Artwork preservation FAQ
Terry Whittier
Archive-name: art-preservation
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WHY GOOD ART GOES BAD - ARTWORK PRESERVATION SECRETS
by Terry Whittier 11/14/94
PREVENTING DAMAGE TO ORIGINAL ART FROM AGING AND CONTAMINATION
There are two main enemies of original art during long-term storage or
display: Chemicals that are contained in the material (whether board or
paper) and what comes in contact with it.
The main enemy from within is the remaining acidity or alkalinity from the
manufacture of the paper or board. Nasty chemicals are usually used to
produce paper products from wood and some plants. Some acidic or alkaline
chemicals can remain in the paper, causing it to chemically change with age
and turn yellow or brown. A paper that is pH neutral is balanced between
acidity and alkalinity (the pH balance) and therefore will tend not to
discolor with age due to interaction with any chemicals contained within the
paper itself. Some papers are buffered, meaning that they have chemicals
added during production that tend to offset the harmful chemicals.
Some papers are 100% rag. These tend to be free of harmful chemicals. Rag
paper is made from fibers other than wood cellulose. These can be made from
cotton, wool, synthetic fibers, etc. These fibers are aligned in one or
more directions (grain) and glued with any of a variety of substances
(sizings). Not all pure rag papers are completely archival (capable of long
life without chemical change or discoloration) but most are.
Some common copier papers are fairly pH neutral. Some are very acidic.
Use a pH testing pen to check them, if you need to.
When buying paper or board, be sure of what you are getting, if you want
archiveability. Or test for pH with a testing device, such as the pH
testing pen offered through Light Impressions supply company for only $6 or
less. It's a good investment...amaze your friends as the dye turns yellow
to indicate highly acidic paper!
Outside nasties are self-adhesive tape, glue, humidity, skin oils,
temperature, aerosols and ultraviolet light.
The sticky coatings on adhesive tape contain volatile chemicals that can
work their way into the paper and stain it. Plus, the adhesive will
eventually dry with age and come loose. The plastic that forms the body of
adhesive tape may also contain solvents that can migrate out and contaminate
the artwork The worst of the commonly used tapes are masking tape and
cellophane tape, although duct tape, drafting tape or any self- stick tapes
are bad.
The best tape to use is pH neutral cloth or paper tape that has a
water-soluable adhesive. This kind of adhesive will not ooze into the paper
of the artwork and can be removed cleanly with a moist cloth.
The best way to secure an original work on a board is with archival corners.
That way, no adhesive touches the art, thus eliminating one major route of
contamination. Using corners made of acid-free paper and secured with
water-soluable adhesive or tape is the best possible mounting technique.
(For added safety, place a sheet of pH neutral paper between the artwork and
the mounting board.) (Matte board is usually pH neutral on the white back
but acidic on the color front and between the faces.) Use spray adhesive
only on a copy or print that you can replace if it deteriorates.
If you write to me, I can send you a free sample of the archival tape that
is available. It can also be simply folded for use as archival corners.
If tape is used directly on the front or back of the original, it is best to
use water-soluble glue tape and as little of it as possible. Keep in mind
that you may want to re-mount the art at some future date and it might be
decided at that time to trim the original to remove adhesive. Leave as much
room as possible around the image for this.
CLEAR OVERLAYING COVERINGS
Glass is the best choice for a clear covering in terms of chemical
contamination. (However, it may shatter if dropped and injure the art.)
Glass that reduces UV transmission is best, as long as any coatings are on
the outside, away from the art. Be sure to clean the covering before
placing it in proximity to the art.
Mylar is the second best option because of its chemical stability.
Polypropylene, Plexiglas, or any of the hard plastic sheets are almost as
good as mylar and will do nicely for a few years before requiring
replacement. Vinyl is the worst choice, since it's the softest and
therefore contains the most potential for contamination.
The softer and more flexible the plastic, for any given thickness, the more
solvents and emulsifiers that it contains. These chemicals evaporate out of
the plastic and sometimes accumulate on the surface of the plastic. Most of
these substances will cause damage or discoloration to artwork as they
accumulate on or chemically combine with the artwork.
To prevent UV light from accelerating the aging of art, avoid direct or very
bright reflected sunlight. It might be wise to avoid very bright fluorescent
lights, particularly daylight types.
ATMOSPHERE
Most art materials and papers are made to be the most stable at room
temperature and between 30% to 40% relative humidity. A little cooler and
drier than this is ideal, but usually hard to maintain. Wide fluctuations
in temperature and humidity are damaging, too. Eliminating oxygen by
encapsulation and replacing the air with nitrogen gas can also help. Many
historic documents are stored this way.
Naturally, any contaminants such as smoke or aerosol chemicals that could
condense on or infiltrate the art must be avoided.
REFERENCES
It is hard to find information about art conservation techniques, but the
catalog of the archival storage supply company, Light Impressions, contains
many micro-articles about the topic. You can write and request a catalog
from them at 439 Monroe Avenue, P.O. Box 940, Rochester, NY 14603-0940.
Permission is granted to reproduce this article for free distribution. I
can send you camera-ready copies. Copyright 1994 by Terry Whittier, 7059
Via Blanca, San Jose, CA 95139 (type font: GillSans 10 pt. in MacWrite)
Assistance from Gerald Perkins.