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This page is maintained by the Sustainability Committee at the American Institute for Conservation of Historic and Artistic Works (AIC). It is intended to provide information about sustainable practices for AIC members, conservation/preservation professionals, and other interested parties within the cultural heritage profession. Please send comments and suggestions to sustainability(at)conservation-us.org.


Introduction

There are many ways to view sustainability and materials. When updating the Sustainability Committee's wikipedia page and sorting information on this topic it became clear that there was no one layout that would satisfy all the possible needs of the reader. For example should information about substituting one solvent for another be grouped with information about using a solvent-free conservation technique? Should information about making your own cotton swabs be placed with information about waste-reduction? Should solvent disposal information be with paper disposal information?

The most obvious solution was to make the information as readily available, and easy to find as possible. As such the information below is specific, unlike the previous pages which were more general and inclusive of all specialty materials. The information below will continue to grow and if/when it becomes difficult to navigate a new format will have to be considered.


Note: The AIC Sustainability Committee does not endorse or promote the companies mentioned. Please feel free to contact us with updates and suggestions, as this list is meant only as an open resource.

Information About Specific Treatments in Conservation

  • Solvent baths for removal of lacquer from metal: Solvent baths of acetone, ethanol, and/or aromatic hydrocarbons are traditionally used to strip protective lacquers from polished metal. Removal of cellulose nitrate-lacquered silver can be accomplished with steam (water) at about 30 psi instead of the traditional solvent baths. The steam removal process is even more efficient if the object can be pre-soaked in warm water. Minimal use of solvent is required to remove remaining traces of lacquer after the steam-cleaning process. In fact, steam stripping of cellulose nitrate lacquer results in a more thorough removal of the material from the metal surface than the use of solvents, either by bath or swab (Thickett and Hockey 2003). Steam is not an effective way to remove acrylic lacquers.
  • Non-solvent techniques for removing adhesives from paper: The Chapter 15: Hinge, Tape, and Adhesive Removal in the Paper Conservation Catalog Wiki gives information about the specific adhesives found in different products and suggests non-solvent techniques for reducing them.
  • Cleaning large surfaces - Use soft natural sponges instead of cotton or wool when cleaning large surfaces, or surfaces that can withstand less specific cleaning, such as stable glazed ceramics or stable stone. Sponges also have the benefit of not leaving fibers behind.

Information About Specific Chemicals in Conservation

Green chemistry technologies are developing substitutions to the petroleum based products that we use. These technologies, supported by the EPA, aim to reduce waste, eliminate "end-of-the-pipe" treatments, offer safer products, reduce use of energy and resources, and supply the consumer with more competitive materials that produce less pollutants. (EPA Green Chemistry page) [1] While newer solvents are being developed, it is worthwhile to consider whether a milder traditional solvent can be substituted in some situations.

How much does the choice of solvent impact impact the environment? Just as conservators have a list of solvents to try in order of least toxic to most toxic, or least polar to most polar, we wanted to make a least green to most green solvent list, but we quickly realized that ranking the environmental impact of solvents is complicated. There are multiple factors to consider and the data available is incomplete.

Solvents

Acetone: has negligible ground level ozone forming properties, is a good alternative to other, more toxic chemicals. It is an acceptable substitute for ozone depleting compounds.

Ammonia: occurs naturally and is produced by human activity. It is a colorless gas with a distinct odor that can be dissolved in water and quickly turns back into gas when exposed to oxygen. It is used as a fertilizer in agriculture.

Xylene: There has been some discussion on the Conservation DistList ([2] search: 'alternative to xylene') about substitutions for xylene in B-72 mixtures. Polypropylene glycol methyl ether was one of the solvents suggested.

Ethanol: Ethanol can be produced industrially using two two methods; the fermentation method is more sustainable than petrochemical processes.

References:

Ankersmit, Hubertus A., and Robert van Langh. 2002. 'The removal of lacquers from silver by steam. 'In Contributions to Conservation, edited by J. A. Mosk and N. H. Tennent, 1-9. London: James & James.

Thickett, David, and Marilyn Hockey. 2003. 'The effects of conservation treatments on the subsequent tarnishing of silver.' In Conservation Science 2002, edited by J.H. Townsend, K. Eremin, and A. Adriaens, 155-161. London: Archetype.

Regarding Substitutions for Solvents in Art

It is worthwhile, as conservators, to be aware that artists are also looking at ways to reduce solvents use. The following websites describe possible solvent substitutions or alterations in technique for making art:

R. Bissett. The Secret to Oil Painting Without Solvents. Retrieved Feb. 2014. [www.buildart.com/secret_paint_without_solvent.htm]

Nontoxic Print: Nontoxic Printmaking, Safe Painting & Printed Art. Safe Solvents (2014). Retrieved March 2014. [3]

Additionally, the National Archives Solvent Solver program uses the principles of Teas Fractional Solubility Parameters to help the user design a mixture of solvents that will have the same properties as a more toxic solvent. Note: this program will work with Windows 95 or later (including Windows 7), but is not Mac compatible.

Surfactants

Regarding Substitutions for Specific Surfactants

Consult the MSDS for specific environmental hazards before using a surfactant. See Stavroudis, Chris. January 2009. Sorting Out Surfactants. WAAC Newsletter (31)1: 18-21 [4] and Stavroudis, Chris. September 2012. More from CAPS3: Surfactants, silicone-based solvents, and microemulsions. WAAC Newsletter (34)3: 24-27 [5]

Triton X- line of surfactants: Use of the Triton X-line is not recommended, as its degradation products adversely affect the environment. (It is an endocrine disruptor that can harm humans, fish, and other organisms). Triton 100X and Triton XL-80N are discontinued. Proper disposal of bulk Triton X products is required.

Surfonic JL-80X: Considered the ‘safe’ non-ionic replacement for discontinued Triton X-100 and Triton XL-80N. According to the MSDS, it is considered moderately toxic to aquatic life but it is not considered hazardous waste. Its biodegradability is undetermined.

ECOSURF EH-line of surfactants: EH-9, EH-6, and EH-3 are non-ionic, low toxicity, and soluble in both water and low polarity solvents. The surfactant is readily biodegradable but the secondary solvent is not. EH-9 may be used a replacement for Triton X-100 or Triton XL-80N.

Surfactant use and disposal tips:

  • Do not dispose of surfactants (even the EH-line) in water or soils.
  • Order small bulk quantities, as very little is typically used.
  • Work in multiples of the surfactants' CMC (Critical Micelle Concentration) to avoid excess quantities.
  • According to Chris Stavroudis, emulsions should be allowed to dry and residue disposed of as solid waste, as the water/solvent mixture will complicate most solvent waste collection programs. For disposal of large emulsion amounts, contact a waste disposal service for further instructions. Additionally, if the emulsion separates- or can be made to separate (perhaps by adding salt)- the organic phase can be removed and combined with waste solvents.

Adhesives

This section is in progress.

Paints

This page [6] created by Golden Artist Colors [7] talks about considerations for disposing of waste in general and also has specific guidelines for disposing of unused acrylic paint.

The sustainability and selection of paints and coatings is discussed by Jean Tétreault in his 2011 article "Sustainable Use of Coatings in Museums and Archives- Some Critical Observations."

Information about Plastics

For more information about recycling plastics, consult the SC article Plastics are Forever and the Recyclability Chart.

Information about Papers and Boards

  • Blotter Paper - Consider whether your use of blotter paper can be replaced with a washable and reuseable material, for example in washing or drying. Some alternatives include Tyvek, Reemay, polyester felts, or other non-woven materials with various qualities, produced under various names.
  • Conservation by Design [8] Ecophant lignin-free and acid-free boxes made from recycled material, and mill board made partially from reused scraps.

Paper Found in Conservation Labs and its Recyclability

In general, the paper materials used in conservation are recyclable if they are made from cellulose, do not contain additional substances (such as dried paints, adhesives, or chemicals), plastic or metal components, or organic material.
Cellulosic paper that can usually be recycled:

  • Office paper (remove staples)
  • Tissue papers (japanese, buffered/unbuffered, packing tissue, interleaving tissues of various trademarked names, etc)
  • Blotter paper and papers formed without adhesives
  • Folders (remove adhesive and labels)


Cellulosic paper that may or may not be recycled:

  • Corrugated boards and pressed millboards (museum-quality, not museum-quality, those of various trademarked names, etc) - This is because these boards are formed with adhesives which are considered a contaminant. Some recycling plants have dedicated machines to recycle these materials or ship them to places that do, others may dispose of boards as trash.
  • Paper towels - This is because of varied recycling regulations and foreign material often found with used paper towels.


Paper that can NOT be recycled

  • Glassine
  • Non-woven polyester (Reemay, Hollytex, Tyvek, etc)

Information about Conservation Supplies and Tools

  • Cotton Swabs - The wooden stick from certain cotton swabs can be used repeatedly. Just use a canister with a small opening to remove the used cotton and roll a new one. Not only does this create less waste, but it is a lot cheaper to buy a package of cotton wool and some bamboo skewers than to buy a box of swabs. The other great advantage of making your own swabs is that you can make customized sizes for what you are working on. Tips for keeping the cotton on is to dip the skewer in distilled water to slightly dampen it before rolling on the cotton, and occasionally sharpen the tip with a rough sandpaper.
  • Plastic or Polyethylene bags - Often polyethylene bags are used for inner packing boxes. Currently some (?) are investigating use of starch-based plastic bags for shipping as they will bio-degrade after use. Another approach is rather than using the usual 2ml polyethylene bags for packing, shifting to using 6ml polyethylene film that can be kept with the inner packing box and re-used every time the box is used which reduces the amount of waste we generate. Along with the use of film, shifting to a lower tack tape that can be re-used and doesn’t tear the film will also reduce waste.
  • Silica Gel - Spent silica gel can be reconditioned in an oven for reuse. Cobalt-chloride self-indicating silica gel is hazardous to the environment when disposed of, so use less of it by mixing it with colorless silica gel. Consider using methyl violet self-indicating silica gel, as it is less toxic. The same is true for for RH indicator cards.

Information about Crates

Some museums have custom crates made for exhibitions, only to discard them once the exhibition is over. Consider offering your crates to a local museum, or listing them on a museum list-serve. Better yet create reusable, modular crates that can be disassembled for easier storage and customized for more frequent use. Turtle Box [9], and Shuert Technologies, [10] are both companies that make reuseable crates.

Sustainable packing and shipping practices for loans and exhibitions depend on the contents. UPS (United Parcel Service) offers suggestions on its website [11] for sustainable packaging of various sized shipments. These types of sustainable packing materials are not appropriate for packaging and shipping artifacts, but would be for shipping additional items associated with the artifacts.

For large shipments, reusable plastic pallets, crates, and bins are available for closed-loop or managed open-loop shipping. Shipping companies, such as UPS' Eco Responsible Packaging Program, offer assistance in identifying and sourcing eco-friendly materials for shipping as well as in designing a sustainable packing and shipping program. The eco-friendly shipping materials are designed of virgin and recycled plastic, wood and metal, and are made to withstand years of heavy use. Cost savings and waste reduction are benefits of using reusable shipping materials.

For small shipments, products made from recycled and recyclable content are available such as: bubble wrap, non-toxic foam, biodegradable twine, biodegradable starch peanuts,and recyclable anti-static peanuts. These materials can in turn be recycled. For example, the UPS Store® participates in recycling peanuts and offers air-filled plastic pillows that can be easily recycled.

Packing and shipping containers can often be reused. 2D typical or standard wooden crates can be refitted to reuse or refitted as temporary storage case for 2D art work such as paintings or framed photographs, drawing. The lid can be replaced with Coroplast corrugated plastic Sheets. Cutouts covered with Hollytex can be made to facilitate the ventilation to minimize the acid build-up from the wood and to keep out the pest.

2D typical or standard wooden travel box commonly placed within the 2D crates can be reuse as housing frame with minor refit. The travel box can be used to accommodate safe handling of painting that do not have frame, a protective cover can be placed on the travel box not on the 2D artwork, the travel box can also be slide in and out of cabinet without damage the bottom of the art work.

Preparation, Art handling, Collection Care Information Network (PACCIN). On the Reuse of Crates. 2/15/2014 http://www.paccin.org/content.php?269-On-the-Reuse-of-Crates[accessed 02/28/2014].

Information about Water

Water Purification and Sustainability

What techniques are used to purify water?

Tap – On demand source; no feedwater waste occasional lab use, general office use, potable, sanitation Quality and content varies according to location Contains VOCs and microbial contaminants Boiling water will kill microorganisms, however it does not remove dissolved ions or particulates.

Filtered – On demand source; occasional lab use, potable Two chief filters of use to conservators are particulate filters and activated charcoal filters.: Amount of feedwater waste correlates with type of filter used. Waste is generally lower than distilled, deionized or reverse osmosis processes. Varying degrees of VOCs and microbial contaminants are removed depending on the filter employed.

Distilled – prepared by heating tap water to create steam. The condensate is collected as product. Distilled is not an on demand source, so it must be made in advance and stored. If the storage container is not made of an inert material, plasticizers will leach out of it and recontaminate the water. Distillation removes all metals, anions, cations, and microorganisms. Distillation eliminates nearly all VOCs. Distillation produces small amounts of water very slowly and uses large amounts of energy and is wasteful of water. Up to 95% waste of feed water; 5% pure product

Deionized can produce moderate volumes of purified water on-demand. While it doesn't produce absolutely pure water, it is convenient and quick, and may be sufficient for many applications. It is an excellent system for removing dissolved solids and gases, although it has a generally poor rating for other impurities. Amount of feedwater waste is much lower than distilled or reverse osmosis, however filters that are re-usable require considerable amounts of water for cleaning purposes. For ultrapure product, deionization systems are often combined with reverse osmosis (RO) systems.

ElectroDeIonized (EDI) water is a continuous water treatment process that removes ionizable species from liquids using voltage applied across a cell. It differs from conventional deionization techiniques in that it is does not require the use of acid, caustic soda, or other chemicals. Deionization can be done continuously and inexpensively using electodeionization.

Reverse Osmosis – depending on system, approx 75% of feedwater is recovered as pure water. While the percentage of feedwater to recovered water is large, the process is very efficient in removing contaminants: RO can remove mineral salts as well as contaminants such as bacteria and pesticides. Reverse osmosis eliminates nearly all VOCs and provides high quality purified water which is suitable for many routine laboratory purposes Product may be prepared in advance and stored for use. The amount of water on demand may be limited by the size of the storage container. If the storage container is not made of an inert material, plasticizers will leach out of it and recontaminate the water.

High Efficiency Reverse Osmosis (HERO) is a proprietary system originally developed to provide ultrapure water. This process was developed for the microelectronics industry. HERO has several potential advantages over conventional RO including greater water recovery – between 95% to 99 %, higher quality product, higher quantity output, and generally lower costs. This is achieved by chemical pretreatment of the feed water undergoing RO. More efficient system than RO, so costs are about 20%–40% less than operating a conventional RO system.

ElectroDeIonization (EDI) is commonly used in conjunction with reverse osmosis (RO) process for ultrapure water. The combination is known as Reverse Osmosis ElectroDeIonization (RO/EDI). Feedwater is first treated by RO. Recovered water is then sent through an electrodeionization cell where voltage is applied across the cell. Output is ultrapure water.

Ultraviolet oxidation is another method that works well as an addition to other systems. It does a good job eliminating bacteria. It works by the use of ultraviolet radiation at the biocidal wavelength of 254 nanometers, which is ‘murder’ on bacteria.


For more in depth discussion of water quality and application, see the Paper Conservation Catalog, [[[BP_Chapter_16_-_Washing#16.3_Materials_and_Equipment| Chapter 16 Water; Quality/Purity]] (pp. 13 – 16 or 16.3.1).

WaterPurificationSystem.jpg

How sustainable are these purification techniques?

The Sustainability Committee has published tables about Water Purification Methods and Environmental Considerations with information that address the following factors:

  • Water discarded during purification (ratio of feed water to purified product)
  • Energy to run purification equipment
  • Energy to make purification equipment and bottles
  • Raw materials to make purification equipment and bottles
  • Disposal of spent filters, equipment, and empty storage containers

To download these tables, go here: Water Charts

Water Use in Conservation

When to use purified water and when to use tap water?

Tap water quality varies by region, and if contaminants are a concern it can be tested. The examples of activities that can be done with tap water assume standard drinkable tap water in the United States.

  • Rinsing silver
  • Rinsing salt contaminated ceramics and stone, except for the last few rinses
  • Inpainting on fill material


Often purified water is necessary in conservation treatments, but not always. Here are a few examples of activities that do require purified water:

  • Mixing reagents
  • Salt test solutions
  • Sample preparation
  • Paper conservation treatments may need purified water, depending on the region and the contaminants in the water. Some conservation use primarily tap water after having the water tested.

Reducing Water Use in Conservation

Another way to go green is to reduce your water use. Here are some ideas of ways to conserve water:

  • If you have an eyewash station, it has to be run regularly to ensure the water is clean and working properly. While it is running, the water can be used to rinse glassware.



References

Tse, Season. Water quality for treatment of paper and textiles. Technical Bulletin 24. Canadian Conservation Institute [Institut canadien de conservation], 2001.

TABLE: 11 Commonly Used Solvents by Stavroudis

Any new solvents used in conservation will have to be vetted to ensure that they are safe to use on and around valuable objects. For the time being, therefore, we will focus on what we know about solvents commonly used in conservation. We chose the top 11 from Chris Stravroutis' list of solvents most used in the conservation community (Chris Stavroudis 2000) and made a chart that takes into account manufacture, environmental impact, disposal implications, and recycling possibilities. The data for columns I - IV comes from the EPA and columns V and VI are based on research done in Switzerland. The chart is not complete, and reflects information available at the time of its writing and the current underdeveloped pollution rating system. The EPA ratings are geared towards US industry and the Swiss ratings consider European disposal and recycling standards, which are not entirely relevant to current US practices.

Note: all are high volume chemicals with production exceeding 1 million pounds per year in the USA except for hydrogen peroxide, which is listed here[12] as “used in at least 8 industries.” This GoodGuide Scorecard was recommended as a website for comparing solvents by a contact at the EPA. (Austin 2010) More about GoodGuide can be found here. [13]

Column I (Health Hazard Ranking) reflects the EPA ratings according to industrial standards, based on relative exposures to large quantities of solvents, as found on the EPA website. [14] The environmental hazard system can be difficult to use for solvent comparisons, especially when trying to apply to art conservation uses. For example, it rates hydrogen peroxide (scored at 52% concentration, not the normal 3% concentration used in conservation) as a worse environmental hazard than toluene, due to its explosive quality at such high concentrations. The “No data” criteria in each of the EPA data columns refers to data that the EPA views as “not toxic enough to comment on.

Column II (Environmental Hazard Ranking System)is based on the GoodGuide Scorecard pollution information “Toxics Release Inventory”. [15] This system ranks 650 chemicals according to 40 different criteria such as air releases, health effects, and ozone depleting potential. (Austin 2010)

Column III (Regulatory Coverage; solvent listed on at least _ lists) addresses the amount of EPA regulatory lists that a solvent appears on. The higher the number, the more environmentally polluting the solvent is rated.

Column IV (Total Environmental Releases in USA pounds/year) was also found on the Solvent Scorecard. [16]

Column V (EHS Score Combined) and Column VI (LCA Score CED) report information taken from work at the Zurich Institute for Chemical and Bioengineering, which resulted in a 2007 publication called What is a green solvent? A comprehensive framework for the environmental assessment of solvents by Christian Capello, Ulrich Fischer, and Konrad Hungerbuhler. [17] The method they developed considers multiple aspects of environmental toxicity. It is promising because it categorizes the issues into two groups: EHS-environmental, health and safety (column V); and LCA- life cycle assessment (column VI), scored according to the cumulative energy demand (CED) required to produce 1 kilogram of the solvent. For both the EHS and LCA, the higher the score, the worse the solvent. To generate their data, they created Ecosolvent -Tool, a computer program [18].

Note: The CED can differ from country to country or processing plant to processing plant, depending on the disposal method -either distillation or incineration, the amount of carbon recovery attained in the disposal process and the amount of solvent recycled or reused. Solvent recycling is the highest variable because it differs country to country and processing plant to processing plant. In Switzerland, they have a 90% carbon recovery rate. In the USA there is no data for recovery, but equipment is available for institutional use to recycle used solvents -relying on the private institution to take action.

In Switzerland, and other European nations, credits are given for solvent distillation because solvent recovery of 90% is assumed, so the higher the carbon fraction of a solvent, the higher environmental credits from solvent incineration. (Capello, Fischer and Hungerbuhler 2007) In the USA, this type of point system has not been established. The EPA pollution control division is hoping to develop a resource that links private companies, allowing individuals and institutions to buy recycled solvents. These would be as clean as “virgin” solvents, but have less environmental impact on the production-end of the lifecycle.

Evaluation of Environmental Impact of Top Solvents Used in Conservation
I. Solvent II. Health Hazard Ranking III. Environmental Hazard Ranking System IV. Regulatory Coverage; solvent listed on at least _ lists V. Total Environmental Releases in USA pounds/year VI. EHS Score Combined VII. LCA Score CED/kg Solvent
Acetone Not Recognized <10 3 No data 3.1 21
Ethanol Not Recognized <4 2 No data 2.6 18
Denatured Alcohol Not Recognized <4 2 No data NA NA
Toluene Developmental Toxicant <2 out of 10 8 64,619,053 3.4 20
Ammonium Hydroxide Respiratory Toxicant <3 2 151,805,024 NA NA
Xylenes Not Recognized <3 out of 10 6 43,243,515 3.4 20
Isopropanol No data <1 out of 8 3 3.1 20
Mineral Spirits No data <3 2 No data NA NA
VM&P Naptha No data <3 1 No data NA NA
Hydrogen Peroxide 52% conc No data <2 out of 5 3 No data NA NA
Stoddard Solvent No data <3 2 No data NA NA


TABLE: Preferred, Useable, and Undesirable Solvent by Alfonsi et al.

Alfonsi et al, in a 2008 article in Green Chemistry [19], broke commonly used solvents into three categories: Preferred; Usable; and Undesirable (see below). Most of the solvents used in conservation fall in to the first two categories but for those that do not, substitutes are encouraged. For example, benzene can be replaced by toluene and hexanes can be replaced by heptane. Shown here:

Preferred Useable Undesirable
Water Cyclohexane Pentane
Acetone Heptane Hexane(s)
Ethanol Toluene Di-isopropyl ether
2-Propanol Methylcyclohexane Diethyl ether
Ethyl acetate Methyl t-butyl ether Dichloromethane
Isopropyl acetate Isooctane Dichloroethane
Methanol Acetonitrile Chloroform
Methyl ethyl ketone 2-MethylTHF Dimethyl formamide
1-Butanol Tetrahydrofuran N-Methylpyrrolidinone
t-Butanol Xylenes Pyridine
Dimethyl sulfoxide Dimethyl acetate
Acetic acid Dioxane
Ethylene glycol Dimethoxyethane
Benzene
Carbon Tetrachloride