BPG Alkalization and Neutralization

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Neutralization: Application of an alkaline agent which reacts with acids in paper to form a salt.

Alkalization: Application of an alkaline agent which reacts with acids in the paper and leaves in paper an alkaline reserve capable of reacting with acids in the future. (Because it enables paper to resist changes in pH, an alkaline reserve is sometimes called a buffer, and the treatment buffering.)

Note: Deacidification, a less precise term, includes the concepts of neutralization, alkalization, and sometimes the removal of soluble acidity by washing.

The purpose of both neutralization and alkalization is to stop acid hydrolysis of the cellulose and associated discoloration, weakening and embrittlement of the paper. Alkalization is also intended to stabilize the paper against further acid attack. Also see the page on Alkalinization of Books.

Original Compilers: Randall Couch
For a full list of the original contributors to this page, see the section below on History of This Page.
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Copyright 2024. The AIC Wiki is a publication of the American Institute for Conservation (AIC). It is published as a convenience for the members of AIC. Publication does not endorse nor recommend any treatments, methods, or techniques described herein. Information on researching with and citing the wiki can be found on the Reference and Bibliography Protocols page.

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American Institute for Conservation (AIC). "BPG Alkalization and Neutralization." AIC Wiki. April 19, 2024. https://www.conservation-wiki.com/wiki/BPG_Alkalization_and_Neutralization.

Factors to Consider

Chemical and mechanical quality of the paper

Degree of inherent instability or expected degradation.

Sources of acidity.

• Local (inks, pigments, etc.)

• General (fiber finish, sizing, environment, etc.)

Effectiveness of prior washing (See Washing)

Housing and storage conditions after treatment

Likelihood of reintroduction of acid due to poor environment.

Effectiveness of buffered housing material in protecting against environmental acidity.

Wet-strength of paper (ability to maintain physical integrity in aqueous/non aqueous alkaline solutions) including areas damaged by acidic media

Permeability of object to aqueous/non-aqueous solutions

Sizing and thickness of object; probable evenness of wetting.

• Laminar structure including mounts and adhesives.

• Possible development of uneven discoloration due to uneven deposition of alkali.

Possibility of changes in aesthetic/optical qualities of paper (color, luster, texture, opacity/translucence)

Problems with solubility of fillers, coatings, sizes, etc. in alkaline solutions (e.g. gelatine, natural gums).

Problems of powdery or crystalline deposits on paper surface after drying.

• Such deposits can sometimes be removed by treatment with a weak volatile acid (carbonated water, dilute acetic acid). Alkaline reserve may be affected.

Problems of color movement/discoloration in paper.

• Presence of groundwood which darkens at alkaline pH.

• Presence of soluble or pH-sensitive material (decomposition products, sizes, dyes, etc.) not previously washed out.

Problems with media (See Media Problems)

Solubility in aqueous/non-aqueous solutions.

Possible color change or increased solubility due to pH sensitivity of media.

Possibility/desirability of protecting against oxidation of cellulose

Possibility of alkaline degradation of paper during treatment

Size and number of objects to be treated

Possible need for bulk treatment apparatus, oversized work area, etc.

Safety factors

Toxicity.

Flammability, explosiveness.

Criteria for Decision to Alkalize

Reasonable evidence of potential damage to the work from acid should exist. This may be provided by ph measurement, fiber analysis, environmental testing, etc. Visual recognition of such inherently acidic paper types as newsprint, or observation of symptoms such as browning and embrittlement, may be adequate given confidence that the work has not been previously alkalized. Environmental conditions to which the work will be returned should be considered.

In deciding whether to alkalize, one must weigh the potential benefit to the specific paper versus its vulnerability to the treatment step itself. Some conservators feel that the beneficial effect of alkalization will be slight for a paper which has already degraded to extreme brittleness, while it may be vulnerable to alkaline degradation such as the peeling reaction during alkaline treatment.

Reasons for the work's selection for preservation should be known and their relative priorities established. Owner or custodian should be consulted.

• Works whose primary value is as historical evidence may suffer from any alteration of their chemical structure. Alkalization may not be appropriate for such works. Papers collected as examples of historic technologies or unusual papermaking materiels are instances of this type.
• The value of book leaves, some manuscripts and certain kinds of paper art may depend upon their ability to withstand flexing, handling or other movement. It may be important to preserve the physical strength of such items, sometimes even at the expense of visual alteration. Occasionally, studies have found an initial drop in paper folding endurance after alkalization, though in subsequent accelerated aging these papers have shown maximum retention of folding endurance. The short term drop in folding endurance may be caused by excess crystals disrupting or abrading the cellulose fibers. The conservator must weigh the trade-off in improved stability on aging versus possible short-term reduced durability.
• Most works of art are valued primarily for their visual effect. This should be preserved in all its subtlety, sometimes even at the expense of loss of physical strength. Alkalizing treatments may be justified if they are not expected to produce visual alterations, or if such alterations are judged to be less significant than those which would occur without treatment. Possible alterations include various shifts in paper color depending on pH and the type of alkaline solution (calcium bicarbonate, magnesium bicarbonate or ammonia water), color shifts in pH-sensitive pigments and colorants (gamboge, turmeric, logwood, cochineal, iron gall inks), decolorization of Prussian blue, blueprints and other alkaline-sensitive colorants. (See Media Problems: chemical sensitivity to pH)

Subsequent planned treatment steps may call for a preliminary alkalization to ensure least damage to the paper.

• The use of bleaches will be more or less damaging to paper depending on its pH. Paper industry research has found a few bleaches such as chlorine dioxide and potassium permanganate are less damaging to cellulose below pH 7. The hypochlorite bleaches, chloramine-T, hydrogen peroxide and sodium borohydride are less damaging above pH 7. Maximum damage occurs to cellulose which passes through neutral pH during bleaching. (See Bleaching.)
• Paper sealed in polyester encapsulations without alkalization has shown reduced permanence after accelerated aging. The deleterious effect can be minimized by adding a sheet with an alkaline reserve within the encapsulation. (See Encapsulation.)

If alkalization is thought appropriate, the object should be tested for stability in specific alkalizing agents and their solvents.

• Testing should demonstrate that the proposed alkalization is compatible with any earlier treatments or with prior steps in the current treatment sequence.
• Testing should make explicit any risks to the paper support. These may include damage to the physical integrity of the sheet or changes in such qualities as texture, color ., etc. (See Factors to Consider.)
• Testing should make explicit any risks to the ground, media or other image components. (See Factors to Consider and Media Problems.)

Criteria for Selecting Alkalizing Method

Chemical objectives of the alkalization treatment.

• Removal of soluble acidity.
• Neutralization of strong acids.
• Neutralization of weak acids.
• Deposition of a moderate alkaline reserve.
• Deposition of maximum alkaline reserve.
• Protection against cellulose oxidation.

Constraints imposed by the materials of the object to be treated.

• Sensitivity to aqueous/non-aqueous solvent. (Permeability, swelling, solubility, desiccation, changes in optical properties. For bindings and other auxiliary supports, adhesives, paper support, fillers, sizings, coatings, image components.)
• Range of pH safety. (Swelling ., solubility ., color changes, saponification of oily ink binders, alkaline hydrolysis and other chemical reactions. For adhesives, auxiliary supports, paper support, fillers, sizings, coatings, image components.)
• Physical compatibility with particles/crystals of alkaline salts. (Abrasion of fibers during flexing, disfiguring surface deposits, changes in optical properties of supports/media. For auxiliary supports, paper support, coatings, image components.)

Practical constraints.

• Number and size of objects to be treated.
• Toxic or hazardous nature of treatment process or chemical residue in treated objects.

Materials and Equipment

Apparatus for mixing chemicals

Apparatus for testing solution strength

• pH measuring device.

• "Drop test" or titration for Mg or Ca with EDTA (see Aqueous Neutralizing/Alkalizing Agents: magnesium bicarbonate below).

Trays

Drying equipment

(see Drying and Flattening)

Brushes

Washing supports/moisture barriers

• Non-woven polyester web.

• Wet-strength paper.

• Polyester film.

Spray equipment

• Aerosol can.

• Pump spray.

• Pressurized commercial cylinder and airless spray gun.

• Air compressor, pressure pot and spray gun/airbrush.

• Pressurized inert gas tank and spray apparatus.

• Cleaning materials for spray equipment.

Ventilation system.

• Fume hood.

• Spray booth.

• Custom-designed system.

Respirator, goggles and gloves for protection against toxic solvents/vapors.

Aqueous Treatment Techniques

Aqueous Neutralizing/Alkalizing Agents

Calcium hydroxide. Formula: Ca(OH)₂. Preparation: An excess (2g/L or more) of high–grade calcium oxide or hydroxide powder is dispersed in purified water, stirred thoroughly, and allowed to settle. This forms a saturated solution with a pH around 12.4. The solution left on its solids remains saturated, but becomes cloudy as insoluble carbonate forms, beginning at the solution/air interface. Any precipitate should be skimmed or filtered before use. For use in treatment the saturated solution is diluted with purified water; the dilute solution forms carbonate much more slowly than the saturated solution and may be stored longer. Commonly employed mixtures range from very dilute (pH @8) up to a 1:1 mixture (about 0.018 N, pH 10–11).

Calcium bicarbonate. Formula: Ca(HCO₃)₂. Preparation: High-grade calcium oxide or hydroxide powder is dispersed in purified water and carbon dioxide is bubbled through this liquid until it becomes clear. About 7.3 g/L of hydroxide powder are required to form a 0.1 M solution. (In practice not all will go into solution because of low solubility.) Use of a large excess of powder will cause difficulty in determining when the reaction is complete. Calcium bicarbonate solutions do not have a long shelf life and should not be used after a visible precipitate begins to form.

Magnesium bicarbonate. Formula: Mg(HCO₃)₂. Preparation: High-grade magnesium hydroxide powder is dispersed in purified water, and carbon dioxide is bubbled through this liquid until it becomes clear. About 5.8 g/L of powder are required to form a 0.1 M solution. Magnesium carbonate (light) may also be used but it is slower to dissolve. (8.4 g/L yield a 0.1M solution). Constant stirring, low temperatures, and maintenance of a pressurized CO₂ atmosphere may be employed to speed up the formation of bicarbonate. Use of a large excess of powder will cause difficulty in determining when the reaction is complete. Settling may be required to eliminate cloudiness. The pH of the solution as applied ranges from 6.5 to 8 depending on age and concentration. Magnesium bicarbonate solutions should not be used after a visible precipitate begins to form (2–5 days in closed container at room temperature). Shelf life may be prolonged by refrigerating the carbonated solution, preferably under a pressurized CO₂ atmosphere.

Testing solution strength: The concentration of finished solution is tested by titration for magnesium with EDTA. Equipment and chemicals for this procedure can be purchased from chemical supply houses, or from Taylor Chemical Co. as the Taylor Total Hardness Set, cat. no. 1123. This set indicates a 0.1 M solution by 18 ml. of titrant. A simpler, less expensive test is available as the Taylor Magnesium Carbonate Drop Test Kit, cat. no. 1597. Both sets may also be used to test calcium carbonate solutions, with suitable modification to the calculations.

Barium hydroxide. Formula: Ba(OH)₂. NOTE: Barium compounds are highly poisonous. One gram of barium carbonate (the residual alkali in this process) ingested is fatal to an adult. Sublethal doses are also toxic. Barium hydroxide-treated material should be so marked and handled with extreme care. Preparation: The solution may be made up in purified water as for calcium hydroxide, although barium hydroxide is slightly more soluble. The pH of the stock solution is around 12.

Magnesium acetate. Formula: Mg(OOCCH₃)₂. Preparation: The solution may be made up in purified water. A 5% (w/v) solution has been described for use alone. A 3% solution may be mixed with 3% calcium acetate in the first bath of a double decomposition treatment. Magnesium acetate has a good shelf life. Both the neutralization reaction and the conversion to the carbonate produce volatile acetic acid, which continues to be generated in treated paper. This may adversely affect lead seals, metalpoint drawings, silver-based photographic images, and lead-based pigments in the presence of sulphur.

Calcium acetate. Formula: Ca(CH₃COO)₂. Preparation: The solution may be made up in purified water. A 6% solution, or a mixture of 3% calcium acetate and 3% magnesium acetate, may be used as the first bath of a double decomposition treatment. Acetic acid is produced in treated paper (see Aqueous Neutralizing/Alkalizing Agents: magnesium acetate).

Calcium chloride. Formula: CaCl₂. Preparation: The solution may be made up in purified water. A 6% (w/v) solution may be used as the first bath of a double decomposition treatment.

Ammonium carbonate (hartshorn). Mixture of ammonium bicarbonate (NH₄HCO₃) and ammonium carbamate (NH₂COONH₄). Preparation: Solution may be made up in purified cool water. A 6% (w/v) solution may be used as the second bath in a double decomposition treatment.

Borax (sodium borate, sodium tetraborate). Formula: Na₂B₄O₇. Preparation: The solution may be made up in purified water. The saturated solution (6.25% w/v) has a pH of 9.5; a 0.01M solution has a pH of 9.2. A 4% (w/v) solution has been employed for alkalizing.

Ammonia water (ammonium hydroxide). Formula: NH₄OH. Preparation: Commercially available as concentrated solution (28–30% NH₃ by weight). Concentrated solution is pH 12. For use in neutralization it is diluted to desired pH with purified water. Ammonia water leaves no residual alkaline reserve.

General Procedures

Paper and media should be tested for solubility and color changes in both water and alkaline solution. Good penetration of alkaline solution is essential. One way to achieve penetration is to wash first in water and treat while still wet. Water in the paper will dilute the alkaline solution and may reduce the alkaline reserve. Wetting agents such as alcohols may be employed to achieve thorough wetting. Powdery or crystalline deposits may form on the paper surface during drying, especially when using concentrated solutions, if solution is left standing on the surface, or conditions favor the movement of salts with the evaporating liquid and their concentration at the evaporation surface. This problem may be ameliorated by a) using a less concentrated solution, perhaps repeating the treatment (drying between) to achieve adequate alkaline reserve; b) drying slowly in a humid atmosphere; c) drying between blotters; d) drying the object face down with only the verso directly exposed to the atmosphere; e) redissolving the deposits in a solution of a weak volatile acid such as carbonated water or dilute acetic acid. Alkaline reserve may be reduced by a, c, or e.

Barrow two-bath process (calcium hydroxide & calcium bicarbonate) Barrow originally employed twenty-minute immersions: saturated calcium hydroxide for neutralization followed by saturated calcium bicarbonate to precipitate the calcium carbonate buffer. The second bath was later deemed superfluous because the hydroxide was converted to carbonate by atmospheric CO₂ during drying. See the section below on Historical Techniques and Materials for updates on the use of this process.

Calcium hydroxide.

• Immersion. Calcium hydroxide is now used in single bath treatments at widely varying concentrations. During removal from the bath, treated paper should be protected from any insoluble carbonate “skin” floating on the liquid surface.

• Brush application. Calcium hydroxide may be applied with a soft wide brush, usually to control or limit penetration (e.g., application from one side only). This method is not usually advantageous for aqueous solutions, since washing is desirable prior to their application. Any alkalizing method which does not completely saturate the paper creates the possibility of uneven distribution. This may result in uneven discoloration of the paper upon subsequent aging.

• Spray. Spray application may be useful to economize on materials, to facilitate rapid treatment of large numbers of items, and to control penetration. Evenness of application is a concern. Spray application can be less efficient than other methods due to premature precipitation of carbonate. This can leave a powdery surface deposit, as well as reducing alkaline reserve.

Barrow/Gear one-step process (magnesium bicarbonate). See the section below on Historical Techniques and Materials for updates on the use of this process.

• Immersion. Barrow recommended a saturated solution of magnesium bicarbonate for spray treatments (see below) and Gear in 1957 introduced a treatment consisting of a thirty-minute immersion in a 0.025M solution of the same agent. The Library of Congress has recommended a minimum concentration of 0.1M to achieve an alkaline reserve of 2–3%.

• Brush application. Magnesium bicarbonate may be applied by brush (see above for description of technique with calcium hydroxide).

• Spray. Magnesium bicarbonate may be applied by spraying (see above for description of technique with calcium hydroxide).

Modification. A. Clapp (1973) has described a treatment in which the paper, supported by a piece of tissue, is placed face down on a sheet of polyethylene and sprayed with a mixture of 90% magnesium bicarbonate solution and 10% alcohol. The damp surface is brushed with a broad soft brush to more evenly distribute the solution. Excess liquid is blotted from the plastic sheet and the paper is covered with tissue and a second sheet of polyethylene. The envelope is closed with “snake” weights and the paper allowed to “marinate” for three to four hours. The envelope is opened and the paper allowed to dry face down.

Barium hydroxide

• Immersion. NOTE: Barium compounds are highly poisonous (see above). Aqueous barium hydroxide was one of the agents employed by O. Schierholtz, whose 1936 patent formed the basis for modern neutralization and alkalization treatments. His immersion times ranged from five seconds to two minutes. Somewhat longer immersion may be necessary for maximum penetration. Extensive premature carbonation of aqueous barium hydroxide solutions may be a problem.

• Brush application. Barium hydroxide solutions may be applied by brush (see above for description of technique with calcium hydroxide).

• Spray. Spray application of barium hydroxide poses a serious health hazard.

Borax.

• Immersion. Borax has been employed in a single bath treatment by F. Flieder and others. M. Hey has reported adverse effects on iron-gall inks and limited improvement in paper strength after moist aging.

• Brush application. Borax solutions may be applied by brush (see above for description of technique with calcium hydroxide).

• Spray. Borax solutions may be applied by spray (see above for description of technique with calcium hydroxide).

Magnesium acetate. Aqueous solutions of magnesium acetate may be employed in immersion, brush and spray treatments.

Double decomposition treatments. These methods, proposed and patented about 1973 by the Library of Congress, were tested but not used for actual treatment.

• Calcium chloride/ammonium carbonate. Paper to be treated is soaked for 10–15 minutes in 6% calcium chloride solution, drained well, and immersed for 15 minutes in 6% ammonium carbonate solution. The second bath should be covered to prevent loss of CO₂ and NH₃. The paper is then washed thoroughly (e.g., 20 minutes in running water followed by four changes of distilled water). The last 10 ml of liquid (roughly) draining from the sheet should be saved in a beaker. 5 drops of 0.025N silver nitrate solution are added to the beaker. If this mixture yields more cloudiness than the same volume of pure water treated with 5 drops of silver nitrate, then residual chloride is present in the paper and it should be washed until the test is negative.

• Magnesium acetate+calcium acetate/ammonium carbonate. Paper to be treated is soaked for 20–30 minutes in a mixture of 3% magnesium acetate and 3% calcium acetate solutions, drained well (perhaps allowed to dry to dampness), and immersed for 20–30 minutes in 6% ammonium carbonate solution. The paper is then rinsed for two hours to remove any excess ammonium carbonate solution.

Ammonia water. Ammonia water in various concentrations may be employed for immersion, brush and spray neutralizing treatments. No alkaline reserve is deposited. Adequate ventilation should be provided to dissipate irritating vapors.

Other Procedures.

• Two-bath treatment (calcium hydroxide & magnesium bircarbonate).

When labor costs permit, immersion in calcium hydroxide solution to effect neutralization and swell the paper fiber may be followed by immersion in concentrated magnesium bicarbonate solution to deposit a large alkaline reserve.

• Double treatment (immersion in aqueous alkali followed by non-aqueous treatmet). After washing and alkalizing with calcium hydroxide or other aqueous agent, a non-aqueous agent such as MMMC may be applied overall or locally in heavily acidic areas (e.g. iron-gall ink). This procedure can be used to produce an extremely high alkaline reserve, and the non-aqueous solvent is less likely to cause movement of salts deposited in the first bath than is a second aqueous treatment.

Non-Aqueous Treatment Techniques

See the section below on Historical Techniques and Materials for updates on the use of Freon.

Non-Aqueous Neutralizing/Alkalizing Agents

Note: The use of magnesium compounds in organic solvents for deacidification is protected by patents (Langwell, Smith). The following information is given in good faith and offers no exemption from proprietary rights.

Magnesium methoxide in methanol. Formula: Mg(OCH₃)₂. Preparation: Commercially available from Wei T'o Associates (on special order) as an 8% solution in methanol. It can also be prepared in the laboratory by adding magnesium to methanol with iodine crystals to act as a catalyst. The iodine evaporates to leave a colorless solution. For use in alkalizing magnesium methoxide is commonly diluted to 1% (about 0.116M) with methanol or other organic solvents. Trichlorotrifluoroethane (Freon) is often used as a diluent because it is a poorer solvent for many media than is methanol. The pH of the solution as used for alkalizing is between 10–11. Magnesium methoxide solutions are extremely sensitive to moisture and should be stored under airtight, moisture-free conditions. They should not be used after a visible precipitate begins to form.

Methylmagnesium carbonate (methoxy magnesium methyl carbonate, or MMMC). Formula (proposed): CH₃OMgOCO₂CH₃XCO₂ (X varies with solvent and temperature). Preparation: This solution is available commercially from Wei T'o Associates. It can be prepared in the laboratory as follows: Carbon dioxide is bubbled through a 1% solution of magnesium methoxide in organic solvents (described above). If pure methanol is employed, the solution will remain clear; the reaction is complete when the solution pH remains steady below 8.5. If a mixture of methanol and Freon is employed, the solution will become cloudy, and the reaction is complete when it becomes completely clear again (pH @ 7.5). Methylmagnesium carbonate solutions are less sensitive to moisture than are magnesium methoxide solutions, to a degree depending upon the solvents used. They should nevertheless be stored under airtight, moisture-free conditions; they should not be used for treatment after a visible precipitate begins to form.

Ethylmagnesium carbonate (ethoxy magnesium ethyl carbonate, or EMEC). This alkalizing agent is available commercially from Wei T'o Associates in two different ethanol/trichlorotrifluoroethane blends. Except for differences in solvent properties (evaporation rate, effect on inks, etc.) its use is similar to MMMC.

Magnesium acetate in methanol. Preparation: Magnesium acetate may be made up as a solution in methanol. Concentrations of 4% (w/v) have been described for alkalization. Acetic acid is formed in treated paper (see Aqueous Neutralizing/Alkalizing Agents: magnesium acetate).

Calcium acetate. Formula: Ca(CH₃COO)₂. Preparation: 2g of high-grade powder are dissolved in 20 ml purified water. 95% ethanol (in water) is slowly added to make 1 liter of solution. If precipitate forms, a few drops of water are added until it clears. Acetic acid is formed in treated paper (see Aqueous Neutralizing/Alkalizing Agents: magnesium acetate).

Barium hydroxide in methanol. NOTE: Barium compounds are highly poisonous. See Aqueous Neutralizing/Alkalizing Agents: barium hydroxide). Preparation: A common formula (1% w/v) is prepared by dissolving 19g of barium hydroxide (octahydrate) per liter of high-grade methyl alcohol. The solution has a pH around 12.

General Procedures

Paper and media should be tested for solubility and color change in the alkalizing solution

Adequate ventilation and safety equipment should be employed. Solvent carriers may be chosen to manipulate penetration rate, toxicity and effects on media.

Magnesium methoxide in methanol, methanol/Freon.

• Immersion. Thorough penetration is essential. Use of poor solvents such as Freon may increase the time necessary to achieve this. Several seconds to a few minutes is usually adequate. Drying (or conducting any portion of this treatment) in a humid environment will encourage undesirable precipitation at the paper surface. Drying between thoroughly dry blotters may help avoid this. Alkaline reserve may be affected.

• Application by brush. This agent may be applied by brush to economize on materials, to minimize vapor exposure and to limit penetration (e.g. application from one side only.) Any alkalizing method which does not completely saturate the paper creates the possibility of uneven distribution. This may result in uneven discoloration of the paper upon subsequent aging.

• Spray application. Spray application may be employed to facilitate the treatment of large numbers of items or paper in bound format, to economize on materials, and to control penetration. All spray equipment should be kept scrupulously clean; clogged nozzles can cause uneven spray patterns and premature precipitation of hydroxide/carbonate. Moisture in the air or in the paper can cause serious problems of precipitation. Several spray systems are available (see Materials and Equipment above); these are often designed for use with specific alkalizing chemicals and can be tailored to the space and production requirements of the conservator or institution.

Methoxy magnesium methyl carbonate in methanol, methanol/Freon. MMMC may be used in immersion, brush and spray treatments (see above for description of technique with magnesium methoxide in methanol). It is less sensitive to moisture than is magnesium methoxide, but caution with regard to humidity and water contact is still advisable.

Ethoxy magnesium ethyl carbonate in ethanol ethanol/Freon. EMEC may be used in immersion, brush and spray treatments (see above for description of technique with magnesium methoxide in methanol). It is less sensitive to moisture than is magnesium methoxide but caution with regard to humidity and water contact is still advisable.

Magnesium acetate in methanol. Methanolic magnesium acetate may be used in immersion, brush and spray treatments (see above for description of technique with magnesium methoxide in methanol).

Calcium acetate in ethanol/water. Paper to be treated is immersed for about 30 minutes in 0.2% (w/v) calcium acetate in ethanol/water (see Non-Aqueous Neutralizing/Alkalizing Agents: calcium acetate above); then allowed to dry in a ventilated area until the smell of acetic acid has disappeared (2 days or longer). The relative proportion of water in the liquid will increase as the paper dries. Areas of water-soluble media should be protected (e.g., blotted). Precipitation of calcium sulphate may be a problem in papers containing high levels of sulphuric acid. If the solution becomes cloudy, the paper should be immersed in a fresh bath of the solution to prevent surface deposition of sulphate.

Barium hydroxide in methanol. NOTE: Barium compounds are highly poisonous (see Aqueous Neutralizing/Alkalizing Agents: barium hydroxide). Methanolic barium hydroxide may be used in immersion and brush treatments. Spray treatment is possible but poses serious health hazard.

Vapor-Phase Treatment Techniques

Vapor Phase Neutralizing/Alkalizing Agents

Ammonia vapor. Ammonia (NH₃) has been used for deacidification. (Kathpalia) It neutralizes incompletely and volatilizes from treated objects in a few months, leaving no alkaline reserve. Observe proper health precautions against vapors.

Cyclohexylamine carbonate (CHC). (Langwell) NOTE: CHC is suspected of being a carcinogen; it may also cause liver/kidney damage. CHC has been used in the form of impregnated sachets and interleaving tissues. It neutralizes effectively but leaves no alkaline reserve. It has an unpleasant odor. Commercially available from interleaf Inc.

Morpholine. In an automated commercial system designed for mass treatment, paper and books to be treated are exposed to a mixture of morpholine vapor and water vapor in an evacuated chamber for ten minutes, after which the excess vapor is flushed and the material removed from the chamber. Morpholine is sufficiently toxic to require special handling equipment, but treated objects are not believed to pose a health hazard. The process neutralizes effectively and imparts some residual alkalinity, but this may diffuse out of the object under even moderately humid conditions. A small percentage of treated materials exhibit color changes, particularly leather and pyroxylin book covers and groundwood papers.

Diethyl Zinc (DEZ). See below under Historical Techniques and Materials.

General Procedures

Currently effective vapor-phase treatments are commercial systems designed for large-scale use. They are not suitable for application by the conservator in the laboratory.

Combined Alkalizing/Strengthening Treatment Techniques

Combined Alkalizing/Strengthening Agents

CMC (sodium carboxymethyl cellulose). Description: Film-forming sodium salt of a polymeric cellulose derivative; high buffering capacity, moderate alkalinity. An aqueous solution, 1% by weight of CMC-12HP and 0.1% of Hercules Kymene, a wet-strength resin, has been used to impregnate paper using a modified mimeograph machine. The effectiveness of any such reinforcing resin depends on the strength remaining in the deteriorated paper (see Consolidation, Fixing, and Facing and Sizing and Resizing).

Magnesium acetate and polyvinyl acetal, polyvinyl butyral, etc. (Regnal process). Paper to be treated is brushed with or immersed in 4–6% magnesium acetate (alkalizing agent) in an organic solvent solution of polyvinyl acetal, polyvinyl butyral, etc. (strengthening resin). Book pages must be separated while drying. Strenghthening achieved is variable.

Magnesium acetate in heat-set adhesive (Postlip lamination tissue). A commercially produced tissue coated on one side with an acrylic or vinylacetate polymer containing magnesium acetate. The tissue is heat-laminated to paper to strengthen it and provide some alkaline protection in one operation.

General Procedures

Heat-set lamination/lining tissues. These may be obtained commercially (Langwell's Postlip) or prepared by thoroughly mixing a suitable alkalizing agent into a heat-set adhesive solution prior to applying it to the tissue.

Lining adhesives. A suitable alkalizing agent may be dissolved in the solvent for aqueous or non-aqueous adhesives (e.g. magnesium bicarbonate solution in water for wheat starch paste; methoxy magnesium methyl carbonate diluted with toluene for PVA resin).

Lining supports. Japanese papers with naturally occurring alkaline fillers have been suggested by A. King for linings using aqueous adhesives. Western or Japanese papers may also be alkalized prior to use as lining supports (they should be allowed to dry thoroughly before beginning the lining process).

Sizings/consolidants. These may be applied as auxiliary consolidants or to replace degraded sizes removed during treatment. Non-aqueous commercial versions are available (Regnal) and both aqeuous and non-aqueous types may be prepared in the laboratory. The alkalizing agent may be the strengthening agent (parchment size, PVA) or an alkalizing agent may be included in the solvent for the strengthening agent (e.g. methoxy magnesium methyl carbonate in methanol for hydroxy propyl cellulose).

Other Treatment Techniques

Mild alkaline wash. This technique, which has been called “calcium replenishment,” employs a wash water that has been made mildly alkaline by passing it through marble chips or by the addition of an agent such as magnesium carbonate. It is not intended to introduce a large new alkaline reserve, but rather to prevent removal of any extant alkaline salts from a paper due to solvent action of the wash water. In this process water pH is typically 8.5 or below.

Historical Techniques and Materials

Diethyl Zinc (DEZ)

In the 1985 print edition of this page, the use of DEZ as a vapor-phase alkalization and neutralization technique was described as being in current use at the Library of Congress. Because DEZ is violently flammable when it comes in contact with either oxygen or water vapor, this technique required special engineering facilities and was not recommended for in-house conservation lab operation. The Library of Congress discontinued its use of DEZ in 1994 due to the technical and financial challenges associated with the process (Harris and Shahani 1994).

General Procedure: Paper and books to be treated are placed in a chamber and partially dried under vacuum and mild heat. Gaseous diethyl zinc is admitted to the evacuated chamber at low pressure to neutralize the acid in the paper fibers and concurrently deposits an alkaline reserve compound. The books are allowed to be treated by the gas for twelve to fifteen hours. After this step the small excess of diethyl zinc is pumped from the chamber and recovered. At this point the treated books are exposed to moist carbon dioxide, which partially converts the zinc oxide left in the paper from the first stage of treatment to zinc carbonate. This leaves an alkaline reserve of about 1.5–2% zinc carbonate/zinc oxide in the treated paper. The treatment also acts as a fungistat to retard mold growth.

Freon (CFCs)

In the 1985 print edition of this page, Freon was suggested as a possible solvent or diluent in certain non-aqueous neutralizing/alkalizing agents. Freon is the brand name for a variety of chlorofluorocarbons (CFCs). In 1987 the Montreal Protocol on Substances that Deplete the Ozone Layer began to phase out the manufacture of CFCs, and the product is no longer available for this application in the United States.

Barrow Two-Step and Barrow One-Step

In her 2003 article, Holly Kruger describes the evolution of treatment practice at the Library of Congress towards the current prevalence of diluted magnesium bicarbonate in an aqueous or ethanol-modified bath. The history of the earlier ""Barrow Two-Step” (concentrated calcium hydroxide, followed by concentrated calcium bicarbonate) and the “Barrow One-Step,” (saturated magnesium bicarbonate) processes with their associated high pH are described as having negative effects on some media, including causing IGI to redden, fade, and/or sink.

Bibliography

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Alkaline sensitivity/​deterioration (peeling, β-elimination), CSC Book Saver, Libertec, magnesium, magnesium-based nonaqueous deacidification, mass deacidification, metal ions added by treatment, Papersave.

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Acid hydrolysis, calcium, calcium hydroxide, deacidification, deionized water, metal ions added by treatment, oxidation, sodium, sodium carbonate.

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Calcium, calcium bicarbonate, deacidification, deionized water, magnesium, magnesium bicarbonate, metals ions added by treatment, tap water.

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Borane tert-butylamine complex/​tert-butylamine borane (TBAB), calcium, calcium propionate (in alcohol), item-level nonaqueous deacidification, metal ions added by treatment.

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Calcium, calcium hydroxide, deacidification, deionized water, sodium.

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Alkaline reserve, calcium, calcium bicarbonate, calcium hydroxide, deacidification, distilled water, magnesium, magnesium-based nonaqueous deacidification, magnesium bicarbonate, methylcellulose, tap water, Wei T’o (carbonated magnesium methoxide).

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Acid-hydrolysis, alkaline sensitivity/​deterioration (peeling, β-elimination), calcium, calcium bicarbonate, calcium chloride, calcium hydroxide, deacidification, metal ions added by treatment, neutralization, sodium borohydride.

Bogaard, John, Hannah R. Morris, and Paul M. Whitmore. 2005. “A Method for the Aqueous Deacidification of Oxidized Paper.” Journal of the American Institute for Conservation 44 (2): 63–74. https://doi.org/10.1179/019713605806082347

Alkaline reserve, calcium, calcium acetate, calcium chloride, calcium hydroxide, calcium nitrate, deacidification, deionized water, metal ions added by treatment, neutralization, sodium, sodium chloride.

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Alkaline reserve, borax, calcium, calcium dichloride, calcium tetraborate, deacidification, distilled water, metal ions added by treatment, sodium, sodium tetraborate

Bukovský, Vladimír. 1997. “Yellowing of Newspaper after Deacidification with Methyl Magnesium Carbonate” Restaurator 18 (1): 25–38. https://doi.org/10.1515/rest.1997.18.1.25.

Item-level nonaqueous deacidification, magnesium, magnesium-based nonaqueous deacidification, metal ions added by treatment, methyl magnesium carbonate

Burgess, Helen D., and Aranka Boronyak-Szaplonczay. 1992. “Uptake of Calcium or Magnesium into Seven Papers during Aqueous Immersion in Calcium or Magnesium Solutions.” In Conference Papers: Manchester 1992, edited by Sheila Fairbrass. London: The Institute of Paper Conservation. 264–72.

Alkaline reserve, calcium, calcium bicarbonate, calcium hydroxide, deacidification, deionized water, distilled water, magnesium, magnesium bicarbonate, magnesium sulfate, metal ions added by treatment, neutralization.

Burgess, Helen D., Stephen Duffy, and Season Tse. 1990. “The Effect of Alkali on the Long-Term Stability of Cellulosic Fibres.” Archivaria 31: 218–23. Accessed August 4, 2022.

Calcium, deacidification, deionized water, distilled water, magnesium, magnesium bicarbonate, magnesium sulfate, metal ions added by treatment, metal ions removed by treatment, neutralization, potassium, sodium.

Burgess, Helen D., Stephen Duffy, and Season Tse. 1991. “Investigation of the Effect of Alkali on Cellulosic Fibres, Part 1: Rag and Processed Wood Pulp Paper.” In Paper and Textiles: The Common Ground; Preprints of the Conference Held at the Burrell Collection, Glasgow, 19-20 September, 1991, edited by Fiona Butterfield and Linda Eaton. Edinburgh: Scottish Society for Conservation & Restoration. 29–47.

Calcium, deacidification, deionized water, neutralization, magnesium, magnesium bicarbonate, magnesium sulfate, metal ions added by treatment, metal ions removed by treatment, neutralization, potassium, sulfur.

Burgess, Helen D., and Douglas M. Goltz. 1994. “Effect of Alkali on the Long-Term Stability of Paper Fibres Containing Lignin.” Archivaria 37: 182–202. Accessed August 4, 2022.

Alkaline reserve, alkaline sensitivity/​deterioration (peeling, β-elimination), deacidification, magnesium, magnesium bicarbonate, magnesium sulfate, metal ions added by treatment, metal ions removed by treatment, neutralization, reverse osmosis water.

Calvini, Paolo, V. Grosso, Margaret Hey, L. Rossi, and Ludvico Santucci. 1988. “Deacidification of Paper—A More Fundamental Approach.” The Paper Conservator 12: 35–39. https://doi.org/10.1080/03094227.1988.9638560.

Alkaline reserve, barium, barium hydroxide, calcium, calcium bicarbonate, calcium hydroxide, deacidification, deionized water, magnesium, magnesium bicarbonate, metal ions added by treatment, sodium, sodium carbonate

Cunha, George M. 1975. "Technical Leaflet 86: Conserving Local Archival Material on a Limited Budget." History News 30 (11): 253–56, 261–64. https://www.jstor.org/stable/42654563

Corbett, W. M.1960. "The Alkaline Degradation of Chemically Modified Cellulose." Journal of the Society of Dyers and Colorists 76 (5): 265–71. https://doi.org/10.1111/j.1478-4408.1960.tb02376.x.

Daniels, Vincent. 1980. "Aqueous Deacidification of Paper." In International Conference on the Conservation of Library and Archive Materials and the Graphic Arts, Cambridge, 22-26 September 1980: Abstracts and Preprints, edited by Guy Petherbridge. London: Institute for Paper Conservation. 121–25.

Daniels, Vincent. 1982. “Colour Changes of Watercolour Pigments During Deacidification.” In “Preprints of the Contributions to the Washington Congress, 3-9 September 1982: Science and Technology in the Service of Conservation.” Supplement, Studies in Conservation 27 (S1): S66–70. https://doi.org/10.1179/sic.1982.27.Supplement-1.66.

Barium, barium hydroxide, calcium, calcium bicarbonate, calcium hydroxide, deacidification, magnesium, magnesium bicarbonate, magnesium-based nonaqueous deacidification, metal ions added by treatment.

DuPuis, R.N., J. E. Kusterer, and R.C. Sproull. 1970. “Evaluation of Langwell's Vapor Phase Deacidification Process.” Restaurator 1 (3):149–64. https://doi.org/10.1515/rest.1970.1.3.149.

Ede, J.R., and W.H. Langwell. 1968. “Sulphur Dioxide and Vapour Phase Deacidification." In Contributions to the London Conference on Museum Climatology, 18-23 September 1967, edited by Garry Thomson. London: International Institute for Conservation of Historic and Artistic Works. 37–40. https://doi.org/10.1179/sic.1967.12.s1.004.

Feller, Robert L., Sang B. Lee, and Mary Curran. 1985. “Three Fundamental Aspects of Cellulose Deterioration." Art and Archaeology Technical Abstracts 22 (S1): 277–354.

Flieder, Françoise, Françoise Leclerc, and Sylvette Bonnassies. 1975. "La désacidification des papiers." Bulletin de l’Institut Royal du Patrimoine Artistique 15: 151–69.

Alkaline reserve, ammonia gas, barium, barium hydroxide, borax, calcium, calcium bicarbonate, calcium hydroxide, deacidification, immersion treatment, item-level nonaqueous deacidification, magnesium, magnesium-based nonaqueous deacidification, magnesium bicarbonate, metal ions added by treatment, not magnesium-based nonaqueous deacidification (Ca/Ba/Zn), Regnal 7P, spray treatment.

Flieder, F., and F. Leclerc. 1972. "Etude du comportement du papier désacidifié par différents procédés." In ICOM Committee for Conservation 3rd Triennial Meeting Madrid Spain 2-7 October 1972. Paris: ICOM. Accessed August 4, 2022
Gerbracht, Amy E., and Irene Brückle. 1997. “The Use of Calcium Bicarbonate and Magnesium Bicarbonate Solutions in Small Conservation Workshops: Survey Results.” Book and Paper Group Annual 16: 15–20.

Alkaline reserve, ammonium hydroxide, calcium, calcium bicarbonate, calcium hydroxide, deacidification, magnesium, magnesium bicarbonate, metal ions added by treatment, neutralization, pH adjustment.

Gilbert, A.F., E. Pavlovova, and W.H. Rapson. 1973. “Mechanism of Magnesium Retardation of Cellulose Degradation During Oxygen Bleaching." TAPPI 56 (6): 95–99.

Golova, O.P., and N.I. Nosova. 1973. “Degradation of Cellulose by Alkaline Oxidation." Russian Chemical Reviews 42 (4): 327–38. https://doi.org/10.1070/RC1973v042n04ABEH002585.

Alkaline sensitivity/​deterioration (peeling, β-elimination), barium, calcium, oxidation, sodium, strontium.

Graminski, E.L., and E.J. Parks. 1981. "The Effect of Calcium Carbonate on the Stability of Acid Treated Papers." Journal of Research of the National Bureau of Standards 86 (3): 309–15.

Acid hydrolysis, alkaline sensitivity/​deterioration (peeling, β-elimination), alkaline reserve, aluminum, deacidification, calcium, deacidification, inorganic fillers, metal ions added by treatment.

Hanson, F.S. 1939.  "Resistance of Paper to Natural Aging." The Paper Industry and Paper World 20: 1157–64.

Acid hydrolysis, calcium, inorganic fillers, iron, linseed oil, metal ions removed by treatment, metallic inclusions/content/traces.

Harris, Kenneth E., and Chandru J. Shahani. 1994. "Mass Deacidification: An Initiative To Refine the Diethyl Zinc Process." Washington, DC: Library of Congress.

This report details the history of DEZ development at the Library of Congress and its discontinuation in 1994.

Hey, Margaret. 1981. “The Deacidification and Stabilization of Irongall Inks.” Restaurator 5 (1–2): 24–44. https://doi.org/https://doi.org/10.1515/rest.1983.5.1-2.24. Accessed August 4, 2022.

Acid hydrolysis, alkaline reserve, barium, borax, calcium, calcium hydroxide, deacidification, iron, item-level nonaqueous deacidification, magnesium, magnesium-based nonaqueous deacidification, metal ions added by treatment, metallic inclusions/content/traces, metallo-gallic inks, methylmagnesium carbonate, sodium.

Hey, Margaret. “The Deacidification and Stabilization of Iron Gall Ink - Cellulose Combinations on Paper." Unpublished report of research performed at the Library of Congress Preservation Research and Testing Office. Washington, D.C.

Hey, Margaret. 1970. "The Use of the Scanning Electron Microscope in Document Restoration Problems." Restaurator 1 (4): 233–44. https://doi.org/10.1515/rest.1970.1.4.233.

Hey, Margaret. 1979. “The Washing and Aqueous Deacidification of Paper.” The Paper Conservator 4 (1): 66–80. https://doi.org/10.1080/03094227.1979.9638520.

Alkaline reserve, alkaline sensitivity/​deterioration (peeling, β-elimination), ammonium hydroxide, borax, calcium, calcium hydroxide, copper, deacidification, deionized water, iron, magnesium, magnesium bicarbonate, metallic inclusions/content/traces, metal ions added by treatment, neutralization, pH adjustment, sodium, tap water, temperature adjustment, wetting agents (alcohols)

Kathpalia, Y.P. 1962. “Deterioration and Conservation of Paper Part IV: Neutralization." Indian Pulp and Paper 17 (4): 226–32.

Kelly, George B., Jr. 1972. “Practical Aspects of Deacidification." Bulletin of the American Institute for Conservation 13 (1): 16–28. Accessed August 4, 2022. https://doi.org/10.2307/3179252.

Acid-hydrolysis, alkaline reserve, ammonia gas, barium, barium hydroxide, calcium, calcium bicarbonate, calcium hydroxide, cyclohexylamine carbonate, deacidification, diethylene triamine,  item-level nonaqueous deacidification, magnesium, magnesium-based nonaqueous deacidification, magnesium bicarbonate, magnesium methoxide, metal ions added by treatment, morpholine, neutralization, not magnesium based nonaqueous deacidification (Ca/Ba/Zn), postlip, sodium, sodium carboxymethyl cellulose.

Kelly, George B., Jr., Lucia C. Tang, and Marta K. Krasnow. 1977. "Methyl Magnesium Carbonate:  An Improved Nonaqueous Deacidification Agent." In Preservation of Paper and Textiles of Historic and Artistic Value: A Symposium Sponsored by the Cellulose, Paper and Textile Division at the 172nd Meeting of the American Chemical Society, San Francisco, California, August 30-31, 1976, edited by John C. Williams. Washington, DC: American Chemical Society. 62–71. Accessed August 4, 2022. doi: 10.1021/ba-1977-0164.ch004.

Kelly, George B., Jr. 1980. “Mass Deacidification With Diethyl Zinc." Library Scene 9 (3): 6–7.

Kelly, George B., Jr., and Stanley Fowler. 1978. “Penetration and Placement of Alkaline Compounds in Solution-Deacidified Paper." Journal of the American Institute for Conservation 17 (2): 33–43. Accessed August 4, 2022. doi: 10.1179/019713678806029184.

Kerr, Nancy, Solomon P. Hersh, and Paul A. Tucker. 1982. “The Use of Alkaline-Buffering Agents to Retard the Degradation of Cotton Textiles.” In “Preprints of the Contributions to the Washington Congress, 3-9 September 1982: Science and Technology in the Service of Conservation.” Supplement, Studies in Conservation 27 (S1): S100–103. doi: https://doi.org/10.1179/sic.1982.27.Supplement-1.100.

Acid hydrolysis, calcium, calcium bicarbonate, calcium hydroxide, deacidification, distilled water, magnesium, magnesium-based nonaqueous deacidification, magnesium bicarbonate, metal ions added by treatment, oxidation, Wei T’o (carbonated magnesium methoxide).

Keyes, Keiko Mizushima. 1982. “Alternatives to Conventional Methods of Reducing on Paper Discoloration in Works of Art on Paper.” Book and Paper Group Annual 1. Accessed August 4, 2022.

Ammonium hydroxide, calcium, calcium hydroxide, deacidification, deionized water, distilled water, light bleaching, localized treatment, magnesium, magnesium bicarbonate, metal ions added by treatment, overall treatment, pH adjustment, suction table/platten, wetting agents (alcohols).

<br. King, Antoinette, Wynne Phelan, and Warren E. Falconer. 1973. "On the Choice of Paper for Lining Works of Art on Ground Wood Pulp Supports." Studies in Conservation 18 (4): 171–74. Accessed August 4, 2022. https://doi.org/10.1179/sic.1973.016

Kolar, Jana, and Gabrijela Novak. 1996. “Effect of Various Deacidification Solutions on the Stability of Cellulose Pulps.” Restaurator 17 (1): 25–31. Accessed August 4, 2022. https://doi.org/10.1515/rest.1996.17.1.25.

Calcium, calcium hydroxide, deacidification, magnesium, magnesium bicarbonate, metal ions added by treatment, Wei T’o (carbonated magnesium methoxide).

Krueger, Holly H. 2003. "Magnesium Revisited." Book and Paper Group Annual 22: 33–39.

Bookkeeper (magnesium oxide), calcium, calcium bicarbonate, calcium hydroxide, deacidification, iron, item-level nonaqueous deacidification, magnesium, magnesium-based nonaqueous deacidification, magnesium bicarbonate, metal ions added by treatment, metallo-gallic inks.

Kusterer, J.E., and R.C. Sproull. 1971. “Gaseous Diffusion Paper Deacidification." US Patent 3,771,958, filed December 30, 1971, and issued November 13, 1973. Accessed August 4, 2022.

Langwell, W.H. 1965.  "Improvements in or Relating to the Preservation of Documents in Storage." British Patent 1,000,981.

Langwell, W.H. 1966. “The Vapor Phase Deacidification of Books and Documents." Journal of the Society of Archivists 3 (3): 137–38. Accessed August 4, 2022. doi: 10.1080/00379816509513832.

Library of Congress. 1978. “The Deacidification and Alkalization of Documents with Magnesium Bicarbonate.” Conservation Workshop Notes on Evolving Procedures, Series 500 (1).

Lienardy, Anne, and Philippe Van Damme. 1990. “Practical Deacidification.” Restaurator 11 (1): 1–21. Accessed August 4, 2022. https://doi.org/https://doi.org/10.1515/rest.1990.11.1.1.

Alkaline reserve, ammonium carbonate, ammonium hydroxide, barium hydroxide, borax, calcium, calcium acetate, calcium bicarbonate, calcium chloride, calcium formiate, calcium hydroxide, cyclohexylamine carbonate, deacidification, diethyl zinc, float/screen treatment, immersion treatment, item-level nonaqueous deacidification, magnesium, magnesium-based nonaqueous deacidification, magnesium acetate, magnesium bicarbonate, magnesium methoxide, mass deacidification, metal ions added by treatment,  methyl magnesium carbonate, morpholine, neutralization, not magnesium-based nonaqueous deacidification (Ca/Ba/Zn), Regnal 7D, Regnal 7P, sodium, sodium bicarbonate, sodium hydroxide, spray/mist treatment, tap water, temperature adjustment, wetting agents (alcohols).

Nielsen, T. F. 1977. "Deacidification, Lamination and the Use of Polyester Film." Archives and Manuscripts 6 (8): 379–81. Accessed August 4, 2022.

O'Loughlin, Elissa. 1992. "Treatment of Two Nineteenth-Century Chromolithographs: An Approach to Reduction of Magnesium Bicarbonate Deposits." Book and Paper Group Annual 11: 126-35.

Deacidification, magnesium, magnesium bicarbonate, metal ions removed by treatment, overall treatment

O’Loughlin, Elissa, and Anne Witty. 1999. “Treatment of Previously Deacidified Paper Artifacts.” In Reversibility - Does It Exist?, edited by Andrew Oddy and Sarah Carroll. London: British Museum. 81–90.

Alkaline reserve, calcium, deacidification, deionized water, item-level non aqueous deacidification, localized treatment, magnesium, magnesium-based nonaqueous deacidification, metal ions added by treatment, metal ions removed by treatment, overall treatment

O'Neill, J. 1979. "The Effective pH on the Yellowing of Lignin-Containing Papers." In Papers Presented at the Art Conservation Training Programs Conference: April 30, May 1 & 2, 1979, Center for Conservation and Technical Studies, Fogg Art Museum, Harvard University, Cambridge, Massachusetts. Cambridge, MA: Center for Conservation and Technical Studies. 139–54.

Plossi Zappalà, Mariagrazia. 1990. “Le propionate de calcium: agent désacidifiant et stabilisant des papiers anciens?” In ICOM Committee for Conservation 9th Triennial Meeting, Dresden, German Democratic Republic, 26-31 August 1990. Paris: ICOM Committee for Conservation. 500–504.

Calcium, calcium propionate, calcium propionate (in alcohol), deacidification, item-level nonaqueous deacidification, metal ions added by treatment

Ralf, Rudolf A.V., R. Dale Ziegler, and Mark F. Adams. 1967. "Archives Document Preservation II." Northwest Science 41: 184–95.

Rouchon, Véronique, and Oulfa Belhadj. 2016. “Calcium Hydrogen Carbonate (Bicarbonate) Deacidification.” Journal of Paper Conservation 17 (3–4): 125–27. Accessed August 4, 2022. https://doi.org/10.1080/18680860.2016.1287406.

Deacidification, calcium, calcium bicarbonate, metal ions added by treatment

Ruggles, M. 1971. “Practical Application of Deacidification Treatment of Works of Art on Paper." Bulletin of the American Group IIC 11 (2): 76–80. Accessed August 4, 2022. https://www.jstor.org/stable/3178898.

Santucci, Ludovico. 1972. "Paper Deacidification Procedures and Their Effects." Colloque International du CNRS sur les techniques de laboratoire dans l’étude des manuscrits 548: 197–212.

Santucci, Ludovico, G. Ventura, and Mariagrazia Zappala-Plossi. 1974. "Evaluation of Some Non-Aqueous Deacidification Methods for Paper Documents." In Etudes concernant la restauration d'archives, de livres et de manuscrits. Brussels: Bibliothèque royale. 131–54.

Smith, Anthony W. 2018. “Aqueous Deacidification of Paper.” In Paper and Water: A Guide for Conservators, 2nd ed., edited by Gerhard Banik and Irene Brückle. Munich: Spiegel. 391–438.

Smith, Richard D. 1977. "Design of a Liquified Gas Mass Deacidification System for Paper and Books." In Preservation of Paper and Textiles of Historic and Artistic Value: A Symposium Sponsored by the Cellulose, Paper and Textile Division at the 172nd Meeting of the American Chemical Society, San Francisco, California, August 30-31, 1976, edited by John C. Williams. Washington, DC: American Chemical Society. 149–58. Accessed August 5, 2022. doi: 10.1021/ba-1977-0164.ch011

Smith, Richard D. 1970. "New Approaches to Preservation." In Deterioration and Preservation of Library Materials: The Thirty-fourth Annual Conference of the Graduate Library School, August 4-6, 1969, edited by Howard W. Winger and Richard D. Smith. Chicago: University of Chicago Press. 139–75.

Smith, Richard D. 1966. "Paper Deacidification: A Preliminary Report." The Library Quarterly 36 (4): 273–79. Accessed August 5, 2022. doi: https://www.jstor.org/stable/4305691.

Smith, Richard D. 1970. "Treatment of Cellulosic Materials." US Patent 3,676,182, filed August 31, 1970, and issued July 11, 1972.

Steczek, Alicija. 2015. “The Uptake of Calcium Carbonate in Paper: Immersion and Float Washing Compared for Selected Paper Samples.” Journal of Paper Conservation 16 (3): 98–111. Accessed August 5, 2022. doi: https://doi.org/10.1080/18680860.2015.1123453.

Alkaline reserve, calcium, calcium bicarbonate, deacidification, float/screen treatment, humidification/pre-wetting, immersion treatment, metal ions added by treatment, neutralization pH adjustment, overall treatment, reverse osmosis water, unrestrained drying.

Stephens, Catherine H., Paul M. Whitmore, Hannah R. Morris, and Theresa Smith. 2009. “Assessing the Risks of Alkaline Damage During Deacidification Treatments of Oxidized Paper.” Journal of the American Institute for Conservation 48 (3): 235–49. Accessed August 5, 2022. doi: https://doi.org/10.1179/019713612804514251.

Alkaline sensitivity/​deterioration (peeling, β-elimination), calcium, calcium hydroxide, deacidification, distilled water, hydrogen peroxide, metal ions added by treatment, oxidation, rinsing, sodium, sodium metaperiodate, tap water, treatment length, UVA radiation.

Stiber Morenus, Linda. 2003. “In Search of a Remedy: History of Treating Iron-Gall Ink at the Library of Congress.” Book and Paper Group Annual 22: 119–25.

Alkaline reserve, Bookkeeper (magnesium oxide), calcium, calcium bicarbonate, calcium hydroxide, calcium phytate, deacidification, deionized water, distilled water, iron, item-level nonaqueous deacidification, magnesium, magnesium-based nonaqueous deacidification, magnesium bicarbonate, metal ions added by treatment, metallic inclusions/content/traces, metallo-gallic inks, methylmagnesium carbonate, neutralization.

Strlič, Matija, and Jana Kolar. 2005. "Review of Practices for Aqueous Paper Deacidification." In 14th Triennial Meeting, The Hague, 12–16 September 2005: Preprints, ICOM Committee for Conservation. London: Earthscan. 231–37.

Calcium, calcium bicarbonate, calcium hydroxide, deacidification, magnesium, magnesium bicarbonate, metal ions added by treatment, potassium bromide, potassium iodide, potassium thiocyanate

Sundholm, Franciska, and Maria Tahvanainen. 2003. “Paper Conservation Using Aqueous Solutions of Calcium Hydroxide/Methyl Cellulose: 1. Preparation of the Solution.” Restaurator 24 (1): 1–17. Accessed August 5, 2022. https://doi.org/10.1515/REST.2003.1.

Alkaline reserve, calcium, calcium hydroxide, deacidification, metal ions added by treatment, methyl cellulose, overall treatment, rinsing

Sundholm, Franciska, and Maria Tahvanainen. 2003. “Paper Conservation Using Aqueous Solutions of Calcium Hydroxide/Methyl Cellulose 2. The Influence of Accelerated Ageing Temperature on Properties of Treated Paper.” Restaurator 24 (3): 178–88. Accessed August 5, 2022. https://doi.org/10.1515/REST.2003.178.

Acid-hydrolysis, alkaline reserve, calcium, calcium hydroxide, deacidification, hydrogen bonding, kinetics/reaction rates, metal ions added by treatment, methyl cellulose, tap water, wet-dry cycles (hornification)

Sundholm, Franciska, and Maria Tahvanainen. 2004. “Paper Conservation Using Aqueous Solutions of Calcium Hydroxide/Methyl Cellulose. 3. The influence on the degradation of papers.” Restaurator 25 (1): 15–25. Accessed August 5, 2020. doi: https://doi.org/10.1515/REST.2004.15.

Acid hydrolysis, alkaline reserve, calcium, calcium hydroxide, deacidification, kinetics/reaction rates, metal ions added by treatment, methyl cellulose, wet-dry cycles (hornification)

Szilard, Jules A. 1973. Bleaching Agents and Techniques. Park Ridge: Noyes Data Corporation.

Tang, Lucia C. 1981. “Washing and Deacidifying Paper in the Same Operation.”  In Preservation of Paper and Textiles of Historic and Artistic Value II: Based on a Symposium Sponsored by the Cellulose, Paper and Textile Division at the 178th Meeting of the American Chemical Society, Washington, D.C., September 10-12, 1979, edited by John C. Williams. Washington DC: American Chemical Society. 63–86. Accessed August 5, 2022. doi: https://doi.org/10.1021/ba-1981-0193.ch007.

Alkaline reserve, calcium, calcium hydroxide, deacidification, deionized water, metal ions added by treatment, neutralization

Tse, Season. 2001. “Effect of Water Washing on Paper and Cellulosic Textiles: An Overview and Update of CCI Research.” Book and Paper Group Annual 20: 35–39.

Alkaline reserve, calcium, calcium bicarbonate, calcium hydroxide, calcium sulfate, deacidification, deionized water, iron, magnesium, magnesium bicarbonate, magnesium sulfate, metal ions added by treatment, metal ions removed by treatment, neutralization, potassium, sodium, tap water

Tse, S., P. Bégin, and E. Kaminska. 2002. “Highlights of Paper Research at the Canadian Conservation Institute.” Studies in Conservation 47 (S3): 193–98. Accessed August 5, 2022. doi: https://doi.org/10.1179/sic.2002.47.s3.040.

Acid hydrolysis, air pollutants, alkaline reserve, butoxytriglycol/​magnesium carbonate, calcium, calcium bicarbonate, calcium hydroxide, deacidification, deionized water, diethyl zinc, FMC-MG3, iron, magnesium, magnesium-based nonaqueous deacidification, magnesium bicarbonate, magnesium sulfate, mass deacidification, metal ions added by treatment, metal ions removed by treatment, neutralization, not magnesium-based nonaqueous deacidification (Ca/Ba/Zn), potassium, sodium, tap water, Wei T’o (carbonated magnesium methoxide)

Williams, John C. 1971. “Chemistry of the Deacidification of Paper." Bulletin of the American Group, IIC 12 (1): 16–32. Accessed August 5, 2022. doi: https://doi.org/10.2307/3178991.

Williams, John C., C.S. Fowler, M.S. Lyon, T. L. Merrill. 1977. “Metal Catalysts in the Oxidative Degradation of Paper." In Preservation of Paper and Textiles of Historic and Artistic Value: A Symposium Sponsored by the Cellulose, Paper and Textile Division at the 172nd Meeting of the American Chemical Society, San Francisco, California, August 30-31, 1976, edited by John C. Williams. Washington, DC: American Chemical Society. 37–61. Accessed August 5, 2022. doi: 10.1021/ba-1977-0164.ch003.

Acid hydrolysis, alkaline reserve, alkaline sensitivity/​deterioration (peeling, β-elimination), calcium, calcium bicarbonate, calcium hydroxide, copper, inorganic fillers, deacidification, magnesium, magnesium bicarbonate, metal ions added by treatment, metallic inclusions/content/traces, neutralization, oxidation, sodium, sodium carbonate

Wilson, William K., Mary C. McKiel, James L. Gear, and Robert H. MacLaren. 1978. “Preparation of Solutions of Magnesium Bicarbonate for Deacidification.” The American Archivist 41 (1): 67–70. https://doi.org/https://www.jstor.org/stable/40292072

Deacidification, magnesium, magnesium bicarbonate, metal ions added by treatment

Wilson, William K. 1979. Preparation of Solutions of Magnesium Bicarbonate for Deacidification of Documents. Washington, D.C.: Preservation Services Laboratory, National Archives of the United States.

Wilson, William K., Ruth A. Golding, R.H. McClaren, and James L. Gear. 1981. “The Effect of Magnesium Bicarbonate Solutions on Various Papers.” In Preservation of Paper and Textiles of Historic and Artistic Value II: Based on a Symposium Sponsored by the Cellulose, Paper and Textile Division at the 178th Meeting of the American Chemical Society, Washington, D.C., September 10-12, 1979, edited by John C. Williams. Washington DC: American Chemical Society. 87–107. Accessed August 5, 2022. doi: https://doi.org/10.1021/ba-1981-0193.ch008.

Aluminum, calcium, deacidification, magnesium, magnesium bicarbonate, metal ions added by treatment, metal ions removed by treatment, tap water

Zachman, Lindsey. 2020. “The Effect of Various Aqueous Bathing Solutions.” Poster presented at the 2020 AIC Annual Meeting.

Calcium, calcium acetate, calcium bicarbonate, calcium hydroxide, citrates (ammonium salts), citrates (sodium salts), conductivity adjustment, deionized water, metal ions added by treatment, metal ions removed by treatment

History of This Page

BPG Wiki
In 2009, the Foundation for Advancement in Conservation (FAIC) launched the AIC Wiki with funding assistance from the National Center for Preservation Technology and Training (NCPTT), a division of the National Parks Service. Along with catalogs from other specialty groups, the published Paper Conservation Catalog and the unpublished Book Conservation Catalog were transcribed into a Wiki environment. In 2017, the BPG Wiki Coordinators reformatted this page by removing the legacy numbered outline format, combining the sections on "Materials and Treatment" and "Treatment Variations", renaming sections, and improving internal links. In addition, two sections (Criteria for Decision to Alkalize and Criteria for Selecting Alkalizing Method), which had been inadvertently skipped during wiki conversion, were returned to the page.

Paper Conservation Catalog (print edition 1984-1994)
Prior to the creation of the AIC Conservation Wiki, this chapter was created in 1985 as Chapter 20: Alkalization and Neutralization of the 2^nd edition of the Paper Conservation Catalog, (print edition 1984-1994) by the following:

Compiler: Randall Couch

Contributors: Marjorie Cohn, Antoinette King, Kitty Nicholson, Robert Parliament, Richard D. Smith, Peter G. Sparks, Dianne van der Reyden.

The 1986 3^rd edition of the Paper Conservation Catalog included two additional sections, "Special Considerations: Criteria for Decision to Alkalize" and "Special Considerations: Criteria for Selecting Alkalizing Method" that were incorporated into the above page.