BPG Glossary of Terms

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This page was created to gather together the various glossaries found in the Paper Conservation Wiki. Included so far are the glossaries from Written Documentation and Adhesives. This page may eventually be merged with the AIC Wiki Lexicon. Readers may also wish to consult CAMEO or the Ligatus Language of Bindings.

Wiki Contributors: Katherine Kelly, Densise Stockman, your name could be here

Copyright 2018. The Book and Paper Group Wiki is a publication of the Book and Paper Group of the American Institute for Conservation of Historic and Artistic Works. It is published as a convenience for the members of the Book and Paper Group. Publication does not endorse nor recommend any treatments, methods, or techniques described herein. There is an ongoing project to update the BPG Wiki. We welcome contributions and feedback. If you would like to get involved in this effort, please contact the wiki team at [email protected].

Glossary from Written Documentation

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This glossary is written for paper conservators, related professionals, and other persons who read written documentation created by paper conservators. The glossary's intent is to define specialized terminology used in condition and treatment reports which is not defined in general dictionaries, either adequately or at all. While a completely standardized vocabulary does not yet exist in the field, this glossary is an attempt to gather terms in general use and their meanings. Some terms are more widely used than others, and usage may vary according to individual conservators. Not included in the glossary are terms describing artist's techniques and media which have been well covered in a growing body of literature, such as William Ivins, How Prints Look, Felix Brunner, A Handbook of Graphic Reproduction Processes, Paul Goldman, Looking at Prints, Drawings and Watercolours, etc.


Abrasion - Damage caused by friction or rubbing action against the paper's surface by a hard, rough or tacky material. May occur accidentally, inadvertently or deliberately, including as a result of cleaning. Surface appearance of abrasion ranges from matte areas, to lifted fibers, to uneven and scratched areas.

Acid-free - State of being neutral or alkaline in pH, often used to describe paper goods used to house art or artifacts.

Acidic - Of or pertaining to a state in which pH is less than pH7. Pure cellulose is initially slightly acidic, but on exposure to light, oxygen, pollutant gasses, and acidic materials in its environment, its pH can drop lower and lower. As a result, the paper loses strength and flexibility, and sometimes changes in color.

Acidity - Chemical state characterized by a pH below pH7; where pH is a reciprocal logarithmic measure of the concentration of hydrogen ions. Acids are chemical substances with a pH below 7, which react with alkalis and can neutralize them. Acids in the presence of moisture degrade paper by causing acid hydrolysis of the cellulose molecule, that is, breaking up of the long cellulose polymer into shorter segments, resulting in paper which is weak and brittle.

Accretion - Foreign material attached to the paper support. In general, it is superficial and rests on top of the substrate; rather than being imbedded. An accretion may cause staining or planar deformation in the support. Examples include mold growth, food, or fecal matter of insects or rodents.

Adhesive - A material which joins surfaces together by adhesive forces. Adhesives may consist of starch, gums, proteins, rubber, shellac or synthetics. Each type has different working properties and chemical characteristics.

Alkaline, alkalinity - Chemical state characterized by a pH above pH7, where pH is a reciprocal logarithmic measure of the concentration of hydrogen ions. Alkaline compounds such as calcium or magnesium salts can protect the cellulose in paper from acid degradation by neutralizing acidity. Alkaline solutions also swell cellulose which can aid in the release of stains and discoloration. Very strong alkalis can degrade the cellulose polymer chain by the peeling reaction. Some colorants are pH sensitive and change color or are decolorized by alkalinity. Physical qualities and long-term strength of papers also depend on the pH of the paper and the percent of alkaline reserve present.

Alkaline reserve - Alkaline earth salts of calcium or magnesium, such as calcium or magnesium carbonate, introduced into paper at its manufacture or in conservation treatment. Calcium and magnesium carbonate are consumed in the process of neutralizing acidity. Their presence assures paper longevity as long as there is an adequate unreacted reserve to neutralize acidity in the future.

Animal glue - An impure, brown protein-based adhesive made from the hooves and cartilage of animals.

Attachments - Integral items or materials (for example, labels, collage elements, etc.), which are adhered locally to the primary support rather than overall.

Auxiliary support - See Supports.


Backing - Material(s) adhered to the back of the primary support. Attachment may be partial or overall. Backings may or may not be original to the support.

Binder - The material which holds pigment particles or dye in a paint or other artist's medium and which helps adhere it to the support. Also called medium.

Blanching - An area of binder which has developed an unintended white or whitish appearance, possibly the result of exposure to moisture or fast-evaporating solvents which occasion local chilling and condensation. Also called bloom, especially in referring to varnish.

Bleeding - Physical movement of non-fast colorants. Usually occurs in the presence of moisture and results in a blurred or feathered appearance. Movement may occur laterally or penetrate to the reverse, which is also called sinking.

Blocking - Condition in which adjacent sheets of paper, e.g. book pages or a stack of sheets, become unintentionally adhered, often because adhesive is present on one or more sheets and has been subjected to pressure while the adhesive is tacky.

Bloom - Opaque or cloudy white appearance on a transparent film of varnish or lacquer which may be related to moisture absorbed in the film.

Break(s) - Scission of paper fibers due to physical weakness in the paper support; generally caused by simple handling and flexing or repeated folding of a very brittle support, in distinction to tearing or cutting.

Buckling - A random deformation in plane, usually concave and convex in appearance. See also cockling.

Buffer - A solution of ions and acids or bases which is capable of maintaining a nearly constant specific pH despite the addition of further acids or bases. In conservation, the term buffered is sometimes used erroneously to refer to the alkaline reserve. It is preferable to refer to the added substance a alkaline reserve and avoid the use of the word buffer in this context. Nonetheless, matboard and paper goods with an alkaline reserve have a history of beingcalled buffered paper or board. The term buffer is also used in describing the effect of certain materials to lessen the shock of sudden change. In discussing environmental conditions for artwork, packaging or housing can be designed and constructed to buffer sudden changes of temperature, relative humidity or shock.

Bulge - A planar distortion or protuberance characterized by a distinct convex formation.

Burnished - Surface area rubbed or polished yielding a shiny and /or smooth appearance. Burnishing may occur accidentally or deliberately.

Burn - Darkening, scorching, embrittlement or destruction caused by heat, fire or certain chemical reactions.


Calender - Manufacturing process of pressing paper or cloth between a set of polished metal rollers in order to give it a very smooth, polished surface.

Card - A medium weight, stiff paper support which generally has a smooth, polished surface due to a manufacturing process known as calendering.

Cellulose - A long-chain carbohydrate polymer found in the walls of plant cells. It is the primary constituent of paper.

Cleavage - Separation or splitting between layers of media, for example, cleavage of paint from a support. See also flaking.

Coating - 1. A material applied to the surface of paper during its manufacture which affects its surface characteristics and enhances its working properties. 2. Application of a material to paper support and/or media for various treatment purposes, such as consolidation, fixing, sizing or varnishing. 3. Application of a material to the paper support and/ or media, at the time the object is produced or at a later date in order to manipulate the visual or working properties of the support or media. (JEK)

Cockling - Deformation of a planar support, generally paper, characterized by multiple alternate concave and convex distortions or ripples, often in parallel ridges.

Collector's mark - An identifying mark, generally a relatively small stamp - inked, embossed or perforated - or a marking applied by some other means, which denotes ownership or provenance.

Compensation - A restoration technique in which losses to the support and/or media are replaced partially or completely, to provide visual continuity and in some cases to enhance structural support.

Consolidation - Reattachment or securing of media which is flaking, cracking and /or friable, by introduction of adhesive or by application of heat, solvent, pressure, and/or adhesive.

Crack - Physical separation or break within one or more layers of a material, often the result of mechanical stress or contraction on drying.

Crease - A line, mark or ridge of paper caused by folding or crushing.

Cut - A sharp-edged break in the paper support, caused by a sharp instrument or object.


Drawing with lead white darkening

Darkening - A shift in color which is darker than the original appearance. May occur as a result of contact with poor quality materials and/or exposure to adverse environmental conditions. The appearance of darkening may be partial or overall.

Deacidification - A general term used to describe treatment steps taken to raise the pH of acidic paper to pH7 (neutral pH) and to pH higher than 7 (alkaline pH). Also called neutralization and alkalization. See also acidity and alkalinity.

Deacidification - can be accomplished by immersion in or by spraying with an aqueous or nonaqueous alkaline solution or suspension, or by deposition of an alkaline earth salt on materials in a vacuum chamber. If deacidification is accomplished by immersion in an alkaline solution, it may also be accompanied by removal of soluble acidity, degradation products, and discoloration.

Deckle edge - A thinner, uneven accumulation of paper fibers at the edge of a paper sheet. It occurs because relatively less paper fiber is deposited along the deckle of the papermaking mold during the manufacture of handmade paper. An imitation deckle edge may be artificially created on machine made paper.


Biological degradation - Deterioration caused by biological factors such as mold, insects, rodents, etc.

Chemical degradation - Deterioration resulting from reaction between primary support and/or media and other chemical species such as atmospheric pollutants, residues from manufacture and poor quality materials.

Physical degradation - Deterioration caused by physical factors such as wear and tear, use, handling, movement, etc.

Deionized water - A type of purified water which has had ions of dissolved chemicals removed by being passed through one or more deionizing columns, filled with compounds which remove the ions into which soluble chemicals disassociate when they dissolve in water. Deionizing columns do not remove solid particles, so particulate filters are needed as well. Most ions removed are harmful to paper, such as iron and copper ions. Deionizing columns also remove calcium, a beneficial ion, which is sometimes added to deionized water for its beneficial effects. Deionized water is not sterile, in contrast to freshly distilled water. See Distilled water.

Delaminate - Lateral separation of a once continuous support or surface into constituent layers.

Dimensions - The size of an object, customarily recorded in the order of height, width, depth. Generally, maximum dimensions are given if portions are missing or support is irregular, identifying where measurements were made.

Desiccated - State characterized by near or total loss of moisture content.

Destructive analysis - A type of analysis in which a sample of material is consumed during testing.

Diffuse - Characterizes a stain which is without distinct edges or boundaries.

Dimpling - Slight indentations in a paper support. Dimpling often occurs when the primary support is partially affixed to a secondary support.

Discoloration - 1. A change or shift from the original color. 2. The chemical or degradation byproduct in the paper which causes the color change.

Discrete - Characterizes a stain which has a distinct edge or boundary.

Distilled water - Water which has been purified by distillation, a process in which water is heated to boiling, the resulting water vapors are carried through a distillation column where the vapors cool, condense and are collected. In distillation, dissolved ions and particulates are both left behind. Freshly distilled water is sterile.

Distortion - A deformation in the plane of the support and/or media.

Dog eared - Crease caused by a single or numerous folds in the corners of paper support.

Draw - Planar distortion usually located in the corners of support. Distortion is characterized by soft undulations resulting from tipped corners onto a secondary support. This manner of attachment prevents free expansion and contraction of the primary support in response to fluctuations in relative humidity.

Dry cleaning - Removal of unimbedded or superficial dirt and grime by eraser cleaning techniques, as opposed to aqueous or solvent treatments. Erasers which might be employed include vinyl (grated or solid), kneaded, rubber or gum. Dry cleaning may also be performed with a brush, cloth or blower. Also called surface cleaning.


Efflorescence - Dissolution, outward migration and precipitation of salts from within a material. These salts are visible on a surface as small crystals or white powdery or crusty deposits.

Embrittlement - Very low folding strength or tendency to break when folded, associated with adverse effects of acids, oxygen, light, heat and residual chemicals from the original manufacture of the paper or after manufacture. See also desiccated.

Encapsulate - To create an enclosure with sealed edges around a paper sheet using two pieces of an auxiliary support, which is generally transparent. The durable, flexible, and very permanent plastic film called polyethylene polyester terephthalate, better known in the U.S. by the brand name Du-Pont Mylar Type D, is currently the preferred auxiliary material for paper objects. The edges may be joined or sealed by heat, ultra sound, 3M 415 double-sided tape or by machine sewing.

Enzyme - A complex protein produced by living organisms that acts as a catalyst in specific chemical reactions, by inducing or speeding such reactions as breaking down and solubilizing starch (amylase), protein (protease), or fat (lipase), etc. Enzymes catalyze but are not consumed in reaction, so very small amounts are necessary. Enzymes generally require moisture to be active, and, in theory, residual enzyme can be reactivated if moisture is supplied. Therefore, after an enzyme treatment step, a thorough rinsing is advised whenever possible and a deactivation step may also be advised in which any remaining enzyme protein is denatured by solvent, heat, etc.

F Fading - Shifts of color in pigments or dyes, generally resulting from exposure to light, but occasionally from changes in pH or exposure to chemicals or pollutants.

False margin - A margin which has been adhered to the edges of the primary support. The margin may consist of individual strips of paper or a single sheet of paper in which the center area has been removed thereby framing the primary support.

Feather, feathering - See Bleeding.

Fill - A technique employed to replace a loss. Fills range from an insert of a like and stable paper, a pulp fill or simply provided by lining. Fills may be considered stabilizing and/or restorative.

Fixative - A coating applied to protect a soluble or friable medium while undertaking other treatment procedures. The fixative coating prevents bleeding or transfer of the medium.

Flaking - Lifting and detaching of clusters of pigment and binder which occurs when a medium loses its binding properties or when it has undergone physical stress. Flaking often results in losses.

Fluorescence - The emission of radiation, generally as visible light, during exposure to a source of radiation of a different wavelength, such as an ultraviolet lamp. Also, the radiation so emitted. In conservation examination, the ultraviolet lamp, also called a black lamp, is used to look for the characteristic fluorescence of iron and iron gall ink (actually black absorption), oils, varnishes, protein glues and sizes, certain pigments or dyes, and mold and foxing growth.

Flyspeck - A dark brown or black accretion of fecal matter produced by insects. Flyspecks appear a small, round, convex droppings; they are often found in clusters. The material is quite acidic and damage caused by staining and deterioration of the support is often irreversible.

Fold - In which one part of the paper support is laid over onto itself. Creasing may or may not accompany a fold.

Footcandle - An English system measure of the intensity of light, based on the light of one candle at a distance of one foot. Used to express recommended light levels for light sensitive media and paper, often in the range of 5 to 10 footcandles. A metric measure of light uses a unit called the lux, which is very approximately 10 times greater than a footcandle, resulting in recommended ranges of 50 to 100 lux.

Foxing - Reddish-brown spots associated with mold growth or metallic specks. Foxing can vary in size and may be round, diffuse or discrete spots. Sometimes the centers of foxing are darker than surrounding areas. Under ultraviolet examination areas of mold growth fluoresce brightly, while iron-rich spots and specks absorb ultraviolet without fluorescence and appear black.

Frass - Chewed material dropped by feeding animals or insects.

Friable - Nature of a material characterized by a loosely bound powdery state. Some media are friable by nature including fabricated and natural chalks and charcoal. Friable states may result from deterioration or desiccation of binder. Also powdering.


Glazing - Protective transparent material used in framing, such as glass, polycarbonate and acrylic sheeting.

Gloss - Surface quality of being very smooth, shiny and reflecting light.

Gouge - Physical damage to support and/or media appearing as a discrete concave distortion, generally accompanied by a spot or linear disruption of the surface. Often the result of sudden impact on a surface, such as with a tool or broken glass.

Grease - A substance which is oily in composition and can penetrate, stain and/or visually disfigure the support and/or media on contact.

Grime - Dirt of a greasy nature. It may be imbedded or superficial.

Gum - A natural secretion from certain plants with adhesive properties. Gums are used as binders and adhesives.


Handling dents - Small creases, often arc-shaped, in a paper support usually resulting from careless handling practices.

Handmade paper - Paper made in the traditional technique, in which a vatman dips a papermaking mold into a vat of paper pulp, catching a fiber slurry which drains to create a mat of intertwined fibers. These fibers, on drying, form a sheet of handmade paper.

Heat-set tissue - A thin tissue paper coated with an adhesive layer which becomes tacky when heated, for example with a handheld tacking iron, and is adhered with light pressure. Developed as an alternative to traditional paper mending techniques. Its use was popularized at the Library of Congress. Their original formulation recommended Barcham Green lens tissue, with a coating of acrylic dispersions Rhoplex AC-73 and Plextol B-500. The paper and adhesives in the Library of Congress formulation are stable and generally easily reversible. Also called Library of Congress heat-set tissue.

Hinge - A folded piece of paper, Japanese paper, linen tape, etc., used to attach a paper artifact to a mount or mat, in such a way that a portion of the hinge is adhered to the back edge of the artifact, while the remaining portion of the hinge is adhered to the surface of a mount or mat. This attachment system can provide good structural support, yet allows safe, ready access to the attachment when it is desired to remove the artifact.

Hole - See Loss.

Humidify - Treatment procedure in which moisture is introduced either as a liquid mist or spray or as water vapor to expand the fiber matrix of the paper support and to allow the release and reforming of hydrogen bonds in the paper support, thus permitting realignment of fibers.


Imbedded - Physical state of a foreign material being irreversibly ground into the support. The material may be intended or unintended.

Incident light - Light falling onto a surface.

Inclusion - Foreign material included within a paper support or other support layer, generally added inadvertently in manufacture.

Infrared radiation - The portion of the electromagnetic spectrum which lies below or beneath visible red, which is invisible and which results in heating when it is absorbed by surfaces. Generally infrared radiation is not useful for visibility and its heating effects are not generally desirable. Infrared examination however can be part of a conservation examination in which carbon based underdrawing is suspected but concealed by heavy layers of paint. As a long wave radiation, infrared is better able to penetrate visually opaque paint layers. When it strikes underlying carbon based drawing, the infrared is absorbed, while it is reflected back by underlying white ground. This differential absorption/reflection can be seen on a vidicon screen and captured by camera, to reveal carbon underdrawings.

Inpainting - A restoration technique in which areas of loss in the media and in some cases in the support are compensated to provide visual continuity. Various artist's media may be employed.

Inscriptions - Information bearing marks or writing which are considered original to the object or which have been added over time.

Insert - A technique used to fill a loss in a paper support, in which a similar weight paper or paper laminate is physically shaped to the contours of a loss, often with a bevel or shelf margin that slightly overlaps the edges of the original thus permitting strong adhesive attachment to the original. Occasionally, inserts are not adhered to the original, but instead attached to a mat backboard directly behind the loss.

Insect damage - Physical damage to support and/or media as a result of destructive contact with insects. Damage may appear as surface thinning, losses or as accretions, such as flyspecks.


Japanese (tissue) paper - A paper support made by traditional Japanese hand papermaking techniques (or by machine in some cases), using traditional Japanese papermaking fibers of kozo (paper mulberry), mitsumata, or gampi. Japanese paper is very strong (has a high tear strength) even in thin weights, because of the very long fibers used to make the paper stock. It generally retains its strength on aging. Japanese paper may be encountered as the primary support, in Eastern or Western art, or as a conservation material. Japanese paper is valued in conservation treatments because its thinness and translucency make it less obtrusive, while its strength and stability on aging lend long-term support to the original.


Lacuna - See Loss.

Laid paper - Paper which is characterized by a grid-like variation in thickness apparent in both raking and transmitted light. The grid consists of chain and laid lines. Chain lines are spaced further apart than laid lines. Laid lines are very close together and run perpendicular to the chain lines. True laid paper is hand made, though machine made paper can be given an impression resembling chain and laid lines through use of a dandyroll in manufacturing. The texture of Western papers is created by the closely spaced copper wires of the papermaking mold surface, while the chain lines result from the fine wire stitching that holds the surface flat. The distribution of paper fibers is thinnest where the laid and chain lines intersect.

Laminate - A layered structure of parallel sheets of various materials, fused or adhered together into one entity. In paper conservation, laminates may refer to layered paper as found in board construction or used to make paper inserts.

Lamination - A reinforcement technique used on paper artifacts, in which one or more layers of transparent material, generally a plastic, are applied overall to the recto and/or verso of the paper artifact. The lamination may be accomplished through the use of plastics and a proprietary adhesive or through thermoplastic materials, such as cellulose acetate, which fuse with heat. Cellulose acetate lamination was introduced in the 1930's by William Barrow. Most examples encountered in the U.S. are cellulose acetate lamination, though other plastics have been used elsewhere. Cellulose acetate laminations can degrade, showing contraction of the plastic film, generally accompanied by a pungent odor of vinegar.

Lamination alters the surface appearance of the paper artifact. Laminations are generally difficult to reverse, requiring strong solvents and/or heat, which may endanger the paper artifact. Newer techniques such as polyester encapsulation and Japanese linings accomplish some of the goals of lamination and are easy to reverse. For these reasons, lamination as defined above has fallen into disuse and disfavor. However under certain circumstances such as extreme fire damage, modern laminating techniques using a thermoplastic adhesive and tissue lamination may be considered an option. (JEK)

Letterpress - A printing method in which dies with individual raised letters are set in sequence in a chase. When paper is placed over the inked form and run through a press, ink transfers to the paper and a inked impression of the letters is made in the paper. Letterpress printing is characterized by recessed inked letters on the recto, and on the verso the impressions if still intact can be felt and seen easily.

Light damage - Reduction of stability of paper support and media caused by (long term or high intensity) exposure to light and ultraviolet radiation. Wavelengths in the ultraviolet region of the electromagnetic spectrum are considered most harmful to paper, however all wavelengths of light are damaging. Light damage is cumulative and its effects may continue in the dark, after intermittent exposure.

Lignin - Polymer which binds together the long cellulose molecules in woody plants. When the plant structure is disrupted in papermaking, lignin becomes unstable, especially on exposure to light or pollutants. Paper and paperboards containing lignin discolor and become increasingly acidic as they age.

Liquid stain - Describes a stain caused by water or moisture. A liquid stain is often characterized by a tideline. See also Tideline.

Loss - Area of the support and/or media which is physically detached or missing.

Lux - See Footcandle.


Mat - As recommended for conservation purposes, a type of protective rigid enclosure for a paper artifact, which is made from a relatively rigid paper board called matboard. While a number of mat structures are possible, the most common structure has two pieces, a front window mat, which has a “window” or opening cut to make the paper artifact visible, and a back board, a solid piece of mat-board the same outer dimensions as the window mat. Generally the window mat is attached to the back matboard with a folded hinge of linen tape applied along the length of one entire side, so that the mat can be readily opened. A mat is always supposed to be larger in length and width than the paper artifact enclosed within it, so that it can protect all edges of the paper. Similarly, the thickness of the window mat is to be greater than the maximum thickness or most protruding part of the artifact, so that the surface of the artifact is also entirely protected from contact or damage. Matboard comes in varying thickness. Four-ply board is most commonly used to make mats, though two-ply is handy for mounts to insert in a window mat, and eight or more plies may be needed to create a window mat that is thicker than a thick or undulating support. Typically a paper artifact is attached to a mat by hinges, though folded corners of paper or polyester may be placed over the corners of the artifact and attached to the mat as well.

Mat burn - A brown line of staining on the support within the aperture of a mat window opening cut from mat board containing lignin. The staining results from the migration of acidic components in the mat board. Also called mat stain.

Matte - Surface appearance which has no shine, reflectiveness or gloss.

Medium/media - 1. Material(s) which comprise the image bearing components of the object. 2. The binder which holds together pigments in a material used to make images.

Mend - A technique used to provide physical stability to a tear or otherwise vulnerable site, generally consisting of a thin reinforcing repair paper and an adhesive to attach it securely to the paper artifact.

Mold - A surface growth of fungus which may have varying color, shape and configuration. It generally proliferates in damp conditions (60% relative humidity or greater) where there is little air circulation. Damage caused by mold includes staining and loss of strength.

Mottled, mottling - Uneven and diffuse discoloration which may appear on both support and media.

Mount - Auxiliary support to which the primary support is partially affixed for storage and exhibition purposes. A window mat may be attached to the mount. It is also the term used in England for mat. (JK)


Newsprint - A smooth, lightweight paper made from unpurified wood pulp fiber stock. Newsprint is acidic and high in lignin. These components contribute to its physical instability and predisposition to darkening with the simple passage of time, and especially when exposed to light and pollutants.

Nonaqueous - A liquid solvent-based system used in treatment in which water is not present.

Nondestructive analysis - A type of analysis during which a sample is not consumed during testing. Nondestructive analysis includes testing in which a sample is removed from the artifact but is not consumed (so that it can be returned to the artifact or used for other analysis), as well as analysis done in situ, without sampling, such as some types of x-ray fluorescence analysis.

Normal light - Light which strikes a surface perpendicularly, e.g. at a 90 degree angle to the surface.


Offset - A mirror image of a paper artifact created by transfer of media or binder to an adjacent sheet of paper, glass, board or plastic film, or by chemical migration of constituents in the paper or medium, such as oil in printer's ink or lignin derived staining.


Paper - A support, generally flexible, made from a liquid suspension of beaten plant fibers deposited on a surface. The primary constituent is cellulose. Paper characteristics vary depending on the quality and chemical stability of fibers and additives and procedures employed in the manufacture.

Papyrus - Support made from overlapped parallel strips of reed plant stalks.

Parchment/vellum - Support made from one of a variety of animal skins, which have been dehaired, soaked in lime, stretched, scraped, and allowed to dry under tension.

Paste - A type of adhesive prepared by cooking starch in water until it forms a thick translucent white suspension. When prepared from purified water and when free of additives, paste has excellent aging properties and can be easily reversed.

Pasteboard - Semi-rigid support consisting of several sheets of paper pasted or adhered together.

Pigment - A finely-divided colorant, which may be derived from a wide variety of substances, organic and inorganic, natural and artificial. Pigments are insoluble in the binder in which they are used, distinguishing them from dyes which are coloring matter that form solutions.

Pith - A smooth white paper-like support which is cut in a spiral from the soft, spongy tissue found in the center of certain plants. Found in Western collections as the support for souvenir depictions of Chinese life. Also called, erroneously, rice paper.

Platemark - The concave impression made in a paper support by a printing plate as it is run through a printing press. Usually printing plates have been copper or zinc plates, of square or rectangular shape with beveled edges to prevent abrupt edges cutting through the paper. No platemark will be created if the paper support is smaller than the plate.

Poultice - A malleable mass or material which absorbs water or other solvents and can be applied to an artifact surface, so as slowly to release solvent and/or to absorb solvent and matter dissolved in it. Poultices can be applied to hold water, solvents or solutions in intimate contact with a surface so as to soften accretions or adhesive. In addition, poultices can function as absorbers of matter dissolved in a solvent, drawing out soluble matter from a surface by virtue of capillarity.

Powdering - Physical state characterized by a loosely bound material. May be used in describing the inherent properties of a media (see Friable) or to describe the appearance of a condition or damage.

Prepared paper - The surface of a paper support which has been covered with an application of a pigmented chalk ground or coating, to prepare it to receive the intended medium.

Pressure-sensitive tape - See Tapes.

Primary support - See Supports.

Puncture - Structural damage to support and/or media. Punctures are generally caused by an impact to the surface and may penetrate, causing a hole.



Raking light - Light source positioned on one side of the support so that the light rakes across the surface. This position creates strong shadows which accentuate textures and deformation of plane. Raking light is distinguished from normal light.

Recto - The right hand side of a book opening. By extension, the front face of a sheet of paper. The front face is also called the obverse.

Relative humidity - The amount of water vapor held by a volume of air relative to the maximum amount which air at that temperature could hold. Expressed as a percentage of the actual water vapor held divided by the maximum water vapor which could be held at that temperature.

Repair - Various treatment techniques which restore structural stability and/or visual continuity to a damaged support or media.

Residue - Remaining portion of a substance after a process, a by-product of a process, not intended as part of the finished artifact. The residue is generally the remains of an attachment that has been removed.

Resizing - Treatment technique in which a sizing material is restored to the support by means of brushing, spraying, or immersion.

Retouch - See Inpainting.


Scratch - Physical surface damage which is narrow and sharp-edged. Scratches often involve a loss of support and/or media.

Scratchboard - A stiff drawing support which has a surface coating of white chalk-like ground, which is covered partially or completely with India ink. The ground enables one to scratch the inked surface, thereby revealing the contrasting color of the underlying layer.

Secondary support - See Supports.

Silking - A form of overall repair and support formerly applied to paper artifacts, which consisted of a layer of fine silk adhered with paste to the verso, and often the recto, of a paper artifact. Because silk is less stable than paper, silking deteriorates faster than the document it was intended to protect and it has been supplanted by other techniques.

Size, sizing - A water-resistant material which is added to paper. Sizing may be added to the pulp slurry during manufacture or as a coating after the sheet is formed. Sizing may also be added in a conservation treatment step as a coating on the surface of paper. Sizing inhibits the absorption of liquid into the fiber matrix, making the paper less susceptible to moisture or the feathering of ink and aqueous media. Sizing substances include gelatin, alum rosin, methyl cellulose, etc.

Skinning - A form of physical damage in which the surface of the paper in an area appears to have lifted up in a continuous thin surface flap.

Smudge - A streak or smear caused by movement of a friable medium or transfer of dirt or grime from another surface or object, i.e. finger smudges. Smudges are generally accidental in nature although they may be intentional.

Solubility - The tendency of aqueous or nonaqueous solvents to dissolve, soften, or swell a substance. Solubility may be complete, as when salt crystals totally disappear into water, or a matter of degree, in which less soluble materials are swelled or softened. Solubility may be desirable in a treatment when a stain, degradation product, or adhesive needs to be removed, but may be problematic when there is undesired vulnerability of media, coatings, collection marks, annotations, etc. which can also be affected by the solvents under consideration. For these reasons, solubility testing should be carried out and documented prior to any solvent treatment.

Split - Physical damage to the support caused by contraction of the support which is held under restraint or when the support sheet ruptures along a previously weakened area such as a fold. Splits usually have the soft-edged appearance of a tear.

Spot test - A small local test using water, solvents, or other materials being considered for use in treatment, which are applied in inconspicuous places on the artifact to determine the possible positive or negative effects on the paper, media, adhesives, etc. present in an artifact.

Stain - A discoloration which lies in the fiber matrix of the support.

Superficial - Resting on the surface of the support or media, not imbedded.

Supports - Conservators distinguish between the sheet or surface which bears the image directly (primary support), an additional sheet which may be adhered to that image bearing sheet (secondary support), and extra materials which lend further rigidity to the former (auxiliary support). Every paper has a primary support but only some have secondary supports or auxiliary supports.

Primary support - The sheet or surface which bears the image directly, generally a sheet of paper for prints, drawings, and manuscripts. The primary support may be a simple sheet of paper or may be adhered to a secondary support, another sheet or surface, which gives additional rigidity and support.

Secondary support - An additional material, often paper or fabric, adhered to the primary support which gives additional rigidity and support, for example, a chine colle print in which a small, very thin paper is adhered onto a thicker, larger sheet, or a map or poster mounted onto linen.

Auxiliary support - Structural materials that lend rigidity and support to the primary support, the surface which bears an image. Examples of auxiliary supports include stretchers, strainers, mats, etc.

Surface cleaning - See Dry cleaning.


Tapa - A beaten sheet material resembling paper which is prepared from the inner bark of the paper mulberry tree, according to methods developed by Pacific islanders.

Tapes - A variety of adhesive-coated materials manufactured in strips and often found on paper art and artifacts as previously-applied mounting or repair materials. Typically, a tape structure consists of a carrier strip of paper, cloth, or plastic, which has an adhesive layer coated on it. Gummed tape has an adhesive which requires moistening to become tacky. Pressure-sensitive tape has a natural or synthetic rubber-like adhesive which is tacky at room temperature and requires only pressure to become adhered to a surface.

Adhesive Transfer Gun (ATG) tape - an adhesive film without a carrier layer, dispensed from a handheld “gun” which transfers tacky adhesive from silicone release paper onto a surface.

Archival tape - so-called “archival tape” varieties are formulated of adhesives which are more stable than typical commercial tapes. Because they can be misused, they are not generally recommended for application on paper art or artifacts.

Cellophane tape - an early form of pressure-sensitive tape, which had a carrier of cellophane, a glossy plastic made of regenerated cellulose, and an unstable adhesive layer very prone to causing oily discolored stains on paper and other surfaces.

Double-sided tape - a form of tape with a very thin carrier that is coated on both sides with pressure-sensitive adhesive. See 3M 415 double- sided tape.

Glassine tape - an early form of gummed repair tape with a carrier of glassine paper, a glossy tan transparent paper.

Linen tape - a form of cloth tape, typically a gummed tape, though some pressure-sensitive varieties are now available.

Masking tape - a form of pressure-sensitive tape with a tan crepe paper carrier. Designed for temporary application, as in masking out areas prior to painting, so generally not stable.

Magic (Mending) tape - a form of tape with a cellulose acetate plastic carrier that has a matte rather than a glossy surface, and an adhesive layer of acrylic adhesive, less prone to discoloring than cellophane tape. Also called frosty tape.

3M type 415 double-sided tape - a form of tape with a very thin carrier that is coated on both sides with a pressure-sensitive adhesive. This adhesive tape has been specified as the recommended adhesive for tape encapsulation. See encapsulate.

Tear - Physical damage which results in a linear or branched separation of the support into partially or completely separate pieces. The resulting edges along the separation have a soft fibrous “feathered” edge, in distinction to a sharp cut edge.

Tenting - Upward lifting in a tent-like curvature of layers which have cleaved, often as a result of shrinkage of the primary support.

Thinning, thin spot - A form of abrasion with marked loss of paper fibers, that makes the paper more translucent to light in the affected area. May be associated with skinning.

Tideline - A stain which occurs when a liquid dries, depositing dissolved material at its perimeter. A tideline is characterized by a discrete edge which is often darker than the remainder of the associated stain.

Transmitted light - Light source positioned beneath or behind the support so that the light shines through the fiber matrix and media. This lighting position allows one to see distribution and density of paper fibers and media, watermarks, chain and laid lines, etc.


Undulation - Planar deformation consisting of soft, gradual distortions which are convex and concave in appearance.

Ultraviolet, uv - A high energy portion of the electromagnetic spectrum, which lies above violet light in the visible spectrum. Ultraviolet radiation is invisible to humans, hence is not correctly called light. It is not necessary for vision and is capable of causing photochemical degradation of many organic materials including cellulose, as well as causing fading of dyes and pigments. For these reasons, ultraviolet radiation present in daylight or the light produced by common light sources such as fluorescent tubes or halogen fixtures should always be filtered to remove ultraviolet in order to prevent photochemical damage and fading of art and artifacts exposed to light. Often abbreviated as uv. See also fluorescence.


Verso - The left hand side of a book opening. By extension the back face of a sheet of paper. The back face is also called the reverse.


Washing - A treatment step in which the paper artifact is immersed in or saturated with water in an attempt to remove soluble degradation products or discoloration and to restore its flexibility.

Watermark - A design created in paper made in a papermaking mold with wire shapes sewn onto its surface. The design is visible in transmitted and/or raking light because paper fibers are more thinly deposited in this area. Machine-made paper can be given an impression resembling a watermark through use of a dandyroll in manufacturing. Chemical watermarks are made by impregnating the manufactured paper support with a transparentizing medium. Watermarks are useful in identifying the origin and age of paper.

Wove paper - Paper which is manufactured (either by hand or by machine) on a screen or with an even mesh. Paper fibers form an evenly distributed matrix of uniform thickness. The sheet may exhibit a faint pattern similar to fabric which is due to the transfer of the texture from the screen or web. Wove paper was introduced in the West around 1750.

Wrinkle - Sharp deformation of paper, angular and irregular appearance, often with broken fibers. (JK)




Glossary from Adhesives

Back to Adhesives
Adhesive - "A substance capable of holding materials together by surface attachment" (Skeist 1977).

Colloid, protective - "Any surface-active substance that prevents the dispersed phase of a suspension from coalescing by forming a thin layer on the surface of each particle" (Hawley 1977).

Gel - "A semisolid system consisting of a network of solid aggregates in which liquid is held" (Skeist 1977).

Glass Transition Temperature (Tg) - "The temperature at which an amorphous material (such as glass or a high polymer) changes from a brittle, vitreous state to a plastic state. Many high polymers, such as the acrylics and their derivatives, have this transition point, which is related to the number of carbon atoms in the ester group" (Hawley 1977).

Retrogradation - "A change of starch pastes from low to high consistency (...comprised...of viscosity, plasticity, and other phenomena) on aging" (Skeist 1977).

Thermoplastic - "A high polymer that softens when exposed to heat and returns to its original condition when cooled to room temperature. Natural substances that exhibit this behavior are crude rubber and a number of waxes; however, the term is usually applied to synthetics such as polyvinyl chloride...linear polyethylene...and cellulosis and acrylic resins" (Hawley 1977).

Thixotropy - "The ability of certain colloidal gels to liquify when agitated (as by shaking or ultrasonic vibration) and to return to the gel form when at rest" (Hawley 1977).


History of This Chapter

BPG Wiki
In 2009, the Foundation of the American Institute for Conservation of Historic and Artistic Works (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 2016, the BPG Wiki Coordinators created this chapter to gather together the various glossaries found in the Paper Conservation Wiki. Included so far are the glossaries from Written Documentation and Adhesives.

Paper Conservation Catalog (print edition 1984-1994)
Prior to the creation of the AIC Conservation Wiki, the Written Documentation chapter was created in 1994 as Chapter 5: Written Documentation (PDF) of the 9th edition of the Paper Conservation Catalog, (print edition 1984-1994) by the following:

Compilers: Holly Krueger, Sarah Melching, Kitty Nicholson
Contributors: Craigen W. Bowen, Irene Brückle, Jane Douglas, Robert Futernick, Margaret Holben Ellis, Karen Garlick, Michelle Hamill, Claire Hoevel, Maria S. Holden, Harold Holland, Jane E. Klinger, John Krill, Cella Manea, Sue Murphy, Maria Pukownick, Pamela Y. Randolph, Nancy Carlson Schrock
Editorial Board: Sylvia R. Albro, Sarah Bertalan, Antoinette Dwan, Holly Krueger, Elizabeth Coombs Leslie, Catherine I. Maynor, Catherine (Kitty) Nicholson, Kimberly Schenck, Ann Seibert, Dianne van der Reyden, Terry Boone Wallis

Prior to the creation of the AIC Conservation Wiki, the Adhesives chapter was created in 1989 as Chapter 46: Adhesives (PDF) of the 6th edition of the Paper Conservation Catalog, (print edition 1984-1994) by the following:

Liaison: Catherine I. Maynor, Diane van der Reyden.
Compilers: Antoinette Dwan, Catherine Nicholson, Christine Smith with Sarah Bertalan, Janet English, Kimberly Schenck, Linda Stiber, Sarah Wagner, Sylvia Rodgers Albro.
Contributors: Cathy Baker, Dan Clement, Debora Mayer, Denise Thomas, Doris Hamburg, Francis Prichett, Frank Mowery, Janet Ruggles, Jill Sterrett, John Krill, Katherine Eirk, Lage Carlson, Lynne Gilliland, Martha M. Smith, Mary Baker, Paula Volent, T.K. McClintock, Tim Vitale
Book and Paper Group Wiki
Using the Wiki

·Contributors Toolbox ·Reference and Bibliography Protocols ·Accessing Conservation Literature (AIC) ·Help Wanted ·Template for New BPG Chapter

Materials and Tips

·Annual Meeting Tips Sessions ·Materials, Equipment, and Tools ·Adhesive Recipes and Tips
·Gels, Thickeners, and Viscosity Modifiers (ECPN) ·Oddy Tests (R&A) ·Instrumental Analysis (Paintings) ·Technical Examination (Paintings) ·Microchemical Testing (R&A)


·Selection for Preservation ·Exhibition, Supports, Transport ·Imaging and Digitization ·Housings ·Encapsulation

Conservation History and Ethics

·Culturally Sensitive Treatment ·Conservation Ethics (AIC) ·History of Conservation and Conservators (AIC)