BPG Backing Removal

Backing removal is the separation of a primary support from an auxiliary support which is structurally, chemically or aesthetically deleterious to the object.
Original Compilers: Pauline Mohr
For a full list of the original contributors to this page, see the section below on History of This Page.
Wiki Contributors: Jennifer Evers, your name could be here
==Factors to Consider==
Sensitivity of media to pressure, moisture, solvent, steam, pH changes. Object may have time-related sensitivity to chosen treatment. Adjust accordingly and use a combination of techniques to maximize safety and effectiveness. 
Strength of original paper support versus that of auxiliary support.
Actual benefits/necessity to re-back.
*Consider extent of adhesive that can be removed after backing removal. Residual adhesive could cause excessive curl and require re-backing of item.
*Fragile support may require re-backing.
Artist's Intent.
Provenance/integrity of auxiliary support. Backing may have artist's signature or comments.
Value of object versus time for backing removal.
*Discuss with curator or owner.
*Bear in mind the current AIC Code of Ethics and Guidelines for Practice.
Quality and composition of adhesive and backing material.
==Materials and Equipment==
===Water or Solvent Bath===
Trays
Used for floating or soaking object. Should be large enough to allow for adequate handling of object and use of additional tools (e.g. spatula) while object is in bath. May need larger trays for tray-within-tray process. (See Enzymes below.)
*Stainless steel, enamel or homemade trays of polyester film or polyethylene are necessary for solvent work.
Support Materials
To permit safe handling of wet object or support on which to float object or surface on which to lay object face down for in-treatment procedures.
*polyester web
*nylon screen 
*polyester film 
Water Source
Should be conveniently located to permit repeated filling and emptying of tray (See Washing).
Blotters
Used to wick water from object.
Miscellaneous
*Sprayer and wetting agent or alcohol to assist in wetting object prior to bathing
*Ammonium hydroxide, calcium hydroxide or magnesium bicarbonate solutions to adjust pH of water bath
*Solvents appropriate to removal of rubber cement, dry mount or non-aqueous adhesive.
===Steam===
Steamer Unit of "Wrinkles Away" or "Steamstress" type available at local hardware or department store. Some conservators recommend use of sodium bicarbonate instead of salt in "Steamstress."
Small easel to permit vertical or near vertical support for object. Allows for more efficient use of steam for certain machines.
Support materials: Blotters, polyester web, etc. to protect face of object and absorb excess steam around its perimeter.
Miscellaneous tools such as spatulas and scalpels to remove loosened backing material and adhesive.
===Enzymes===
Appropriate enzyme
Thermometer
Support materials such as polyester web, glass or Plexiglas, depending on method of treatment.
Miscellaneous: water, trays, blotters, etc. (See Water or Solvent Bath)
===Humidification===
Humidity chamber
*Can be easily made with plexiglas, polyester film or polyethylene and wood, large trays, etc. 
*Wet blotters or an ultrasonic humidifier are alternative methods to achieving humidification (see Humidification).
Support materials
*Polyester web to protect face of object against any possible condensation
*Nylon support screen on which to rest object above source of moisture.
Water and tray 
To serve as source of moisture.
Measuring devices
*Humidity indicating papers
*Machine to measure humidity level.
===Poulticing===
*Cellulose ether or starch powder and water to make a paste to locally “wet” an area in a more controlled manner.
===Dry Removal===
Splitting, sanding, heating, or freezing. 
Hand tools
*Scalpels
*Spatulas (metal, bamboo, Teflon) for removal of backing board material. 
*some conservators believe that contact of the paper with steel tools is potentially harmful due to possible deposit of iron particles.
Working surface
*Portable board, glass or plexiglas on which to attach item if working face down.
*Tape for attachment
*Plexiglas or glass would permit checking of depth of backing during removal.
Lamp
*Table or floor, especially useful for raking light illumination if object is face up. 
*Permits viewing “depth” of spatula while working. 
Light box 
*For viewing “depth” of backing during removal if object is secured face down to clear support.
Weights and blotters or tape 
*To hold object in place while working. 
*Prevents slippage from applied pressure of scalpel or spatulas.
 Heat source 
Can be used to soften adhesive such as rubber cement or dry mount tissue.
*Hot air gun
*Hair dryer 
*Heated spatula 
Cold source
To neutralize or reduce tack of heat-sensitive adhesives. 
*Dry ice or freon (See Historical Techniques and Materials)
Miscellaneous 
*Rubber cement pickup, erasers, sandpaper, electric sander, cotton and water or solvent to remove residual adhesive
*Polyester web, glassine, silicone paper to protect front of object while working face down or to insert between back of object and backing while treatment is in progress after partial removal of backing material.
==Wet Treatment Techniques==
===Soaking===
Used if strength of paper support and insensitivity of media to prolonged contact with water has been determined to be safe. 
1. Determine safety of media with water and advisable handling procedures for wet paper. (See Media Problems, Spot Tests, and Washing). Preliminary treatment may provide possibility of immersion. (See Consolidation, Fixing, and Facing).
2. Reduce bulk of backing if it seems necessary or appreciably beneficial. This may be determined by thickness, density, absorbency of backing material and actual area of adhesion (ie. object may only be partially affixed at perimeter); assumed strength of adhesive bonding; or expandability, fragility or sensitivity of object. 
*Spot test or spray object and backing to determine above-mentioned properties.
*Remove excess material, using appropriate dry techniques. (See Dry Treatment Techniques).
*Partial attachment of item to backing may lead to uneven expansion of original when placed in water bath. Recommend manual removal prior to bathing and maximum reduction of extraneous material to extent safely possible.
3. Prepare water bath. Adjust temperature and pH as desired. 
*Pre-spray with alcohol or alcohol/water mixture. The addition of a wetting agent to water or use of tepid water may increase responsiveness of item to treatment. Test media and paper for safety with alcohol; alcohol may “move” sizing or degradation products, leading to tidelines, ringing or spotting.
*Adjust pH to 8–8.5 with addition of ammonium hydroxide or neutralizing agent. Protein glue will swell more easily (See Alkalization and Neutralization).
*Employ appropriate enzyme if desired.
4. Immerse object face up on chosen support material. Gentle movement of water over the object or manipulation of object or tool may facilitate removal as the adhesive bond is softened.
*Bathing time will be determined by properties of individual item. Discoloration of water is a good indication of the need for continued bathing. Change or adjust bath as required.
*If adhesive is tough or absorbency of material is low the object might be removed periodically to gradually peel away extraneous material before re-immersing and continuing.
5. Remove residual adhesive as possible. This may be accomplished with object in or out of bath, face down on support, as dictated by object's properties and choice of support material.
*Manipulate with fingertips, moist cotton, stainless steel spatula, blotters, etc.
*Re-immerse and repeat as necessary.
6. Dry or flatten as desired (See Drying and Flattening).
===Floating===
Used if original paper support is extremely thin or fragile or media is somewhat sensitive to prolonged contact with water.
Follow steps 1, 2, and 3. as in above in Soaking.
Support and float the item:
Choose support such as polyester web, polyester film and/or nylon screening stretched onto a frame as determined by item. Polyester film may float away from object during treatment but can be gently realigned for removal of object from bath.
Spray item lightly if possible and place on support. This will insure more uniform expansion of both original and backing and should guard against any ringing or depositing of stain onto original as capillary action moves water up from the reverse once floating begins.
Adjust water level in tray.
*Low level is easier to control.
*If using screen, adjust water level so that a thin film of water just covers the top surface of the screen.
Holding support diagonally at corners, carefully lay item down onto water surface. Allow to remain still. If using a framed screen support, can gently rock tray or lift screen at intervals to increase water flow if desired.
Remove periodically from bath to remove extraneous material and repeat procedure as necessary. Follow directions as in 4, 5. and 6. as above in Soaking, substituting "float" for "immerse."
===Steaming===
Used if media is relatively sensitive to water and/or if proteinaceous glue has been used to attach the backing material. Paste, unlike glue, will not respond so well with the additional heat supplied by steaming.
Test sensitivity of media to moisture and friction.
Remove bulk of backing material with scalpel or spatula.
Secure object face down onto blotter support by taping or pinning (not through item!) or weighting as desired. May use small easel for angled vertical working to maximize vertical rising of steam.
Steam object.
*While steaming, tease off backing material with spatula or scalpel. Area of working and time for removal will be determined by item.
*May prepare local area for steaming by moistening with methyl cellulose or water or preliminary run with steamer over larger area to allow some steam to penetrate before principal “attack” in a smaller area.
*Residual bits of adhesive or backing may be removed afterward with moist cotton, methyl-cellulose application and/or scalpel as determined by object.
*Since exposed original will absorb steam, direct steam accordingly to avoid possible tide lines or damage to sensitive media. May cover partially with blotter to help guard against this.
*Object will be temporarily deformed after steaming but can be flattened and dried as appropriate.
===Enzymes===
Used especially when original paper support is too fragile to tolerate much manual manipulation or adhesive responds very slowly or inadequately to water alone.
Research preliminary information, procedures and appropriateness to object.
May be used in combination with above procedures of Soaking, Floating, or Steaming.
*Enzyme solution may be sprayed on front and/or back of item as preparatory step to soaking or floating.
Proceed, following appropriate chosen treatment.
===Humidification===
Used if original support is very fragile, media is very sensitive to actual contact with water, or removal of thick or dense backing material would be facilitated by slow moisture absorbency as preliminary step to another technique.
May employ a moisture chamber to assist softening and swelling of hygroscopic adhesive such as protein glue. May make viscous methylcellulose poultice to slowly humidify and soften backing material for removal.
*Place object in chamber as in normal relaxation technique. See Humidification.
*Allow to remain overnight or for similar time period.
Remove item from chamber and proceed as in one of the above procedures.
===Solvent Bath===
Used if backing has been secured with a dry mount tissue, rubber cement or similar non-aqueous adhesive.
Test sensitivity of media to chosen solvent. If unsafe, proceed with one of the dry techniques.
Reduce bulk of backing as possible as in Splitting, Heating, Hot Spatula, or Freezing.
Prepare solvent bath. Be sure that tray material is safe with solvent. If not, a temporary tray can be constructed out of polyester film (Mylar) or polyethylene sheeting and rigid side supports.
Immerse object face up on chosen support material. 
*Gentle movement of solvent or tray may facilitate removal.
*Bathing time will be determined by properties of individual item. 
*Discoloration of solvent or presence of adhesive residue on object or tray bottom will indicate effectiveness of treatment. 
*Change or adjust bath as required.
Allow to air dry to truly see results of treatment. Solvent will temporarily cause paper to look translucent. 
*Repeat if necessary.
Should an adhesive be impossible to dissolve (e.g. some synthetic emulsions) it may be possible to swell it and then manually remove it with a rubber cement pickup, plastic eraser or scalpel. Some adhesive may remain.
==Dry Treatment Techniques==
===Scraping===
Used if media cannot tolerate any contact with moisture or solvent necessary to effect removal. 
1. Place item face down on support material such as polyester web, silicone paper, blotter or glass as seems appropriate to item. Tape around edges to portable board or table if desirable and/or possible.
2. Weight to prevent slippage while pressure is exerted by scalpel or spatula movements.
3. Commence removal of layer(s) by pushing or pulling cutting tool as preferred or determined by composition of backing material.
*Take extra caution with backings composed of miscellaneous particulate matter that can “catch” the tool's progress.
*Change scalpel blades or sharpen spatula as necessary to maximize working time and safety of object.
*Adjust tools as proceeding. A large spatula is often good for the beginning stages and a sharper scalpel or smaller spatula better as the back of the original artwork is approached.
*Work as evenly as possible. Best to work down overall layers evenly to prevent undue pulling or pressure on original as the interface of the backing and artwork is approached. Occasional checking on a light box may be useful.
4. Residual bits of backing material and/or adhesive may be removed with scalpel, sandpaper or moist cotton as determined by object.
===Sanding===
Used if backing is very thin and media cannot tolerate any contact with moisture or solvent. Probably used most frequently as a last step to another dry technique. 
Follow 1 and 2 as in Scraping.
Commence removal with coarsest sandpaper as possible (e.g. 80 or 100) and work towards a finer grade as the back of the original artwork is approached. Some conservators employ an electric sander for this purpose.
While working remove residual “dust” with brush or controlled vacuum. Wear protective dust mask while working.
===Splitting===
Used if media is sensitive to moisture or solvent necessary to soften adhesive and/or if backing must be preserved. Probably used most frequently as a preliminary step to another dry technique or a solvent bath to reduce the residual adhesive.
Use only if original paper is strong or thick, backing material is easily fractured in even layers or is much weaker than the original and/or adhesion between original and backing is very weak.
With item face up secure item very well to prevent slippage. 
*Best done with taping to table if margin is available; otherwise, weight well, protecting face of item. 
*Use raking light illumination to assist in seeing the “depth” of the spatula or folder employed.
Choose appropriate tool and method of working
*A Teflon spatula may permit smooth action but is probably thicker than a metal one; a metal spatula may provide the necessary “cut” through the material. 
*Push or pull the tool in small, interrupted arc-like patterns as seems to be most effective, keeping the tool as flat and parallel to the paper as possible. 
*Once one is underway and proceeding safely, the strokes can be elongated to cover a larger area. 
*The procedure may appear to be easier in one direction than another due to the grain of the material being split.
Proceed as above in Scraping or Sanding and approach the artwork from the back if splitting method seems unsafe.
If the separation does not occur exactly at the adhesive interface remove residual backing material and adhesive as in Scraping or Sanding.
===Heating, Hot Spatula===
Used most frequently if backing has been attached with a dry mount tissue. 
Determine appropriateness of procedure (i.e. heat sensitivity of adhesive).
Secure item face up to working surface with tape or weight as possible. 
Begin at one corner and direct heat between item and backing.
*While holding hot air gun or heated spatula with one hand loosen adhesive bond with spatula held in other hand or by carefully pulling up on item.
*As removal proceeds, insert silicone paper between object and backing to prevent re-adhering.
When completed, remove residual adhesive with additional heat, eraser, rubber cement pickup or solvent as appropriate. 
*If dry mount tissue still adheres to reverse of object, reduce manually with scalpel or sandpaper and follow with adhesive removal as possible, dry or with solvent. 
*It may be impossible to remove the tissue without abrading the back of the artwork if the paper is very fibrous.
===Freezing===
Also used most frequently if backing has been secured with a dry mount tissue. 
May use as “other-side-of-the-coin” technique to Heating, Hot Spatula. 
Follow procedures as in Heating, Hot Spatula substituting canned Freon for heat source. (See Historical Techniques and Materials)
Using dry ice:
*Protect face of item with polyester film to avoid possible condensation on paper.
*Protecting hands as necessary, lay dry ice on surface and leave for short period of time.
*Remove and check for release of adhesive. 
*Repeat if necessary; otherwise, insert silicone paper into loosened area and proceed.
*When completed remove residual adhesive with additional heat, eraser, rubber cement pickup or solvent as appropriate.
==Case Studies==
A large number of Arthur Dove watercolors have been mounted with rubber cement. His ink signature has been noted to be partially soluble in ethanol.
==Historical Techniques and Materials==
In the 1985 print edition of this page, the use of Freon was suggested as a possible technique for dry backing removal. 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.
==Bibliography==
ASTM (American Society for Testing and Materials). 1963. Paper and Paperboard Characteristics, Nomenclature, and Significance of Tests. 3rd Edition. Technical Publication No. 60-B. Philadelphia : ASTM.
Baker, Cathleen A. 1984. "Methylcellulose and Sodium Carboxymethylcellulose: An Evaluation for Use in Paper Conservation Through Accelerated Aging." Studies in Conservation 29(Issue Sup1): 55-59.
Browning, Bertie Lee. 1969. Analysis of Paper. Marcel Dekker Inc. 
Burgess, Helen D. and Carmen L Charette. 1983. "The Use of Fixatives to Protect Fugitive Colourants During Conservation Treatments." In AIC Preprints. American Institute for Conservation 11th Annual Meeting, Baltimore. Washington, DC : AIC. 129-139.
Clapp, Anne. 1973. Curatorial Care of Works of Art on Paper. Oberlin, OH: The Intermuseum Laboratory. Accessed August 25, 2020.
DeSantis, Pia. 1983. "Some Observations on the Use of Enzymes in Paper Conservation." Journal of the American Institute for Conservation 23(1): 7-27. Accessed August 25, 2020. 
Glazer, Mary Todd. 1980. "Conservation of Drawings by Frank Lloyd Wright at the New England Document Conservation Center." In AIC Preprints. American Institute for Conservation 8th Annual Meeting, San Francisco. Washington, DC : AIC. 20-25.
Goodwin, Mary. 1981. "Conservation of the Tattooed Lady, a Collage by Peter Blake." The Conservator 5(1): 9-11.
Haner, Paul, Quentin Rankin, and Timothy J. Vitale. 1980. "Paintings on Paper: A Dialogue in Five Case Histories." In AIC Preprints. American Institute for Conservation 8th Annual Meeting, San Francisco. Washington, DC : AIC. 26-38.
Keyes, Keiko. 1978. "The Unique Qualities of Paper as an Artifact in Conservation." The Paper Conservator 3(1): 4-8.
Lepeltier, Robert. 1977. The Restorer's Handbook of Drawings and Prints. Van Nostrand Reinhold Company. 
McKetta, John J. 1973. Wood, Paper, Textiles, Plastics and Photographic Materials. Barnes and Noble Books.
Price, Lois Olcott. 1981. "Patch Picture for Dr. Physick: The History, Analysis, and Treatment of a Trompe 1'Oeil Watercolor." In AIC Preprints. American Institute for Conservation 9th Annual Meeting, Philadelphia. Washington DC : AIC. 153-163.
Sumira, Sylvia, Alan Derbyshire, and Lindsay Farrimond. 1983. "A Technique for the Removal of Glue Residues and Light Backings from Non-immersible Objects Using Enzymes." Paper Conservation News 26:(1) 2.
Williams, John. 1981. Preservation of Paper and Textiles of Historic and Artistic Value II. Advances in Chemistry Series 193. Washington, DC : American Chemical Society.
==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, Jennifer Evers reformatted this page by removing the legacy numbered outline format and improving internal links.
Paper Conservation Catalog (print edition 1984-1994)
Prior to the creation of the AIC Conservation Wiki, this chapter was created in 1985 as Chapter 24: Backing Removal of the 2nd edition of the Paper Conservation Catalog, (print edition 1984-1994) by the following:
:Compiler: Pauline Mohr
:Contributors: Meredith Mickelson and Doris Hamburg
Category:Materials and TreatmentCategory:Book & Paper
Category:Paper
Category:Treatment
Category:Backing Removal