DIP Online
Designs Ink Publishing
Article Archive and Reference Library
Articles by Chris A.
Paschke, CPF GCF CMG
"Vellum and Parchment"
February 1999
For years there have been
assorted techniques promoted for the mounting of 'sheepskins' and generally
there is more than one way to skin a cat.
But in order to better understand the positives and negatives of
attempting to mount parchment we need to first examine the origin and
differences of this tricky animal.
HISTORY
The use of vellum animal
skins for recording history has long been an accepted practice, and skins have
survived from as early as Egypt 2500 BC.
Calf, goat and sheep were normally used, but skins of gazelle, antelope,
stag and ostrich have been uncovered and preserved. Vellum is the proper name given for any high
quality animal skin excluding sheep or lamb.
Though all writing skins are often referred to as 'parchment', the only
true parchment comes from sheep.
In ancient times the
preparation of skins for writing was crude.
Archbishop Hildeberg of Tours in the 11th century tells that
prior to writing on skin the scribe cleaned remains of fat and other impurities
with a razor then pumiced it with a stone to smooth and remove tendon
lines. On the other hand, it was said
that Cicero had an extensive library of parchment in which there existed a
parchment so fine that the whole story of The Iliad was written upon it and
fitted into a nutshell.
PARCHMENT IS SHEEPSKIN
Genuine sheepskin parchment
is used for printing, writing and bookbinding whenever excellence or
distinction is desired. This is the
reason many ivy league universities continue to produce diplomas on original
sheepskin instead of artificial parchment or fine grade printing paper.
The skins from sheep are
whiter and oilier than vellum. To
prepare them sheepskins are first pickled for storage then in large batches are
depickled, scraped, limed, then finally squeezed to remove moisture. Skins are then tied to a wooden frame at 21
points around the edge of the skin, and allowed to dry 5-6 days. The skins are then scraped (for the second
and third times), degreased, shaved, pumiced, purified, and whitened, all by
hand. Then they are set aside to dry
slowly to ensure a flat even skin. Dried
skins are cut from the wooden frame for finishing and/or cutting into smaller
pieces.
VELLUM
Though the process for
preparing vellum is similar to sheepskin, while sheepskins are sorted and
selected after dewooling, calfskins and goatskins are selected prior to
dehairing. After the hair has been
removed, there is a long liming process lasting up to four weeks. Shaving of vellums takes much longer and is
more difficult, requiring much greater skill for it is easy to remove too much
or too little of the skin reducing its value.
New skins are generally
stored rolled and reverse rolling will lie them flat. Most vellums are sold as whole skins unlike
sheepskin parchment which is also available in rectangular shapes. Vellums are generally creamy in color and
often showcase the veining of the animal, while parchment is whiter and has a
much smoother surface. Unlike paper,
the preparation of natural animal skin cannot be mechanized.
PARCHMENT AND VELLUM TODAY
Though the use of animal
skins appears to be more limited to university diplomas in the United States,
in other parts of the world it is extensively used for everything from wedding
invitations to royal proclamations (photo 1).
Skins are sought after for their longevity because of their
photo 1
This 1852 sheepskin parchment
ledger sheet has been encouraged to curl
through the application of
tolerable heat (180 degrees F), but excessive pressure.
complete lack of acidity due
to the cleaning and purification processes.
No two skins are truly alike.
This in turn is part of their natural beauty and the basis for framing
them true to their nature...unmounted.
Fully mounting a piece of parchment or vellum using any process
restricts it from the natural expansion and contraction it craves through
variations in relative humidity.
Preservationally, a skin document or diploma should be hinged or
conservationally mounted. If a document
is slightly buckled it is the nature of the beast and is truly a part of the
total effect and appearance, it should be allowed to thrive.
FLATTENING FOR CONSERVATION HANDLING
If a cracked, wrinkled, or
rolled document has been brought in and needs to be made flat, the best advice
for the framer is to be very careful about offering to mount it at all. Moistening and flattening procedures on this
type of project often should be contracted to a book or paper conservator in
your area. Relaxing and flattening a
badly damaged document may involve soaking in water then slowly drying between
Pellon and blotters beneath a weight. If
it has become dry and brittle forcing it flat could crack it.
There are many areas that
require testing prior to submerging any skin document, such as testing for ink
and paint permanence, or wax seals. Also
skins will react differently depending upon what animal they are but more so
how they were prepared for use in the first place.
For help in locating a
conservator in your area contact the American Institute for the Conservation of
Historical and Artistic Works, 1400 16th Street NW, Suite 340,
Washington, D.C. 20036.
FLATTENING WITH MOISTURE AND PRESSURE
Since vellums are originally
dried on frames much like stretcher bars, when dampened they will cockle and
warp, and attempt to revert to the original shape of the animal as they dry (if
left to dry under no restraints). So to
reflatten vellum, it must be dampened and dried under tension or pressure, such
as plate glass weights (photo 2). But
even flattened skins will buckle again with increased relative moisture.
photo 2
This 5x7" vellum sample was first soaked in
distilled water
then allowed to freely air dry under no pressure, encouraging
it to cockle (lower right corner).
Left side was then pressed flat at 160F using a
mechanical press. The top portion was then
dry mounted to 4ply mat board using BufferMount tissue
at 165F for 3 minutes and cooled
under a glass weight.
Simple flattening of a slightly
cockled or warped piece is very easy to do by a framer. Skins may be redampened to relax them in an
attempt to reflatten prior to framing.
Tests should still be done on the document prior to dampening to
determine the permanence of the inks and pigments used. With a dampened Q-tip, touch each individual
color lightly to check for bleeding or lifting of color.
A humidifier is a great way to
moisten a document. A makeshift
humidifier may be made with two plastic garbage tanks, the larger one having a
lid. Place the smaller in the larger and
surround it with a moat of water, keep the smaller inner one dry. Place the document in the dry tub and close
the lid. It will relax as it absorbs the
moisture in the tank.
Heavily dampening parchment will
both effect the surface finish and may shrink the skin, about 5% overall (photo
3). To lessen these dramatic effects,
use the lightly dampened blotter method by pressing it to the skin for just a
few seconds. Then press the parchment
between clean, dry blotters, placing a sheet of Pellon between the skin and the
blotter, under even weight like that of a closed (not locked) cold mechanical press
or piece of plate glass large enough to cover the entire piece.
photo 3
The left sample illustrates a piece of sheepskin that
has been dampened and air-dried.
There is about 5% natural shrinkage due to the original
stretched cleaning process.
The right sample shows the unfortunate damage resulting
in applying both moisture
and heat to the parchment at the same time.
A 50/50 solution of alcohol and
distilled water may also be used during the dampening process, and dampening
may be done from the back of the document with a cotton ball, squeezed sponge,
or mist bottle. Another version is
transferring moisture into the skin by moistening a blotter and then placing it
in contact with the back of the skin, but be careful this can bond to the
document if left too long.
Change the blotters every 1/2
hour if very soaked, 4 hours if misted, until completely dry. Do not leave damp blotters in contact for
extended periods to the skin as it promotes mold growth. Most skins will water stain (some worse than
others) so spot dampening should always be avoided and parchment will
definitely want to curl.
Parchment is much more delicate
than vellum and reacts much more violently when mishandled. Predictability is the key, always know what
will happen prior to doing anything. Many
applications (ie: moisture and heat) individually are quite safe, but when
applied in collaboration can be deadly to that "one-of-a-kind"
sheepskin ledger page from 1852 (again, photo 3).
IF YOU MUST MOUNT
Occasionally the customer
will dogmatically announce they want it flat, regardless of its natural tendency
to buckle through moisture expansion.
Although mounting is often possible, it should be discouraged. These are often one of a kind collectibles or
originals and should be treated as such.
Documents, certificates and diplomas
should be treated in the same manner as a fine art original. Museum mounting using all the standard
conservation methods of hinging with wheat starch and Japanese hinges on only
acid-free 4-ply boards should always be stressed. Slight buckling of a skin with natural
temperature and humidity changes truly is the nature of the beast.
Other options for mounting
depending on the skins include: stretching over coated bars or acid-free museum
board and affixing to the back; wet mounting with adhesives specified for
skins; and dry mounting. Additional heat
applications involve Lamin-all (a heat setting wet glue) and Parchweld. Both of these last two methods involves a
combination of taping, heat and pressure.
Even when vellum is stretched like canvas it will cockle as time passes
and the natural effects of the above mentioned temperature and humidity tighten
and relax it. Of course the ideal
environment is 60-70F with 50% relative humidity.
HEAT APPLICATIONS
But if the plunge is taken and the risks are all
understood, then often parchment may be mounted using many methods. None will be preservation, or reversible. When a dogmatic client pursues the more static
and flat look, dry mounting fully dried skins with low temperature, removable,
acid-free tissues is quite simple and effectively successful. Acceptable dry mount tissues include
BufferMount, TM-4, Drychival or Acid Free Mounting Adhesive.
Vellum
will notoriously tolerate much greater temperature and moisture abuse than
parchment. Applying heat alone to skins
will not radically effect them as long as it is not too hot. Tests show that temperatures of 180F for up
to 5 minutes will not do damage to either vellum or parchment samples, although
a tendency toward brittleness does begin to occur. High temperatures of over 200F will be asking
for trouble, for parchment could literally be fried, it is a real skin. Care should always be taken when applying
heat of any kind, though 160F for 3 minutes to set any low temperature tissue
is very safe (photo 2, sheepskin onto BufferMount).
A
combination of heat and pressure while damp will slightly shrink most vellum
(almost undetectably), while it may do major damage to parchment (photo
3). Make certain any skin having been
dampened to flatten is totally dry and clean of all other adhesives prior to
mounting to avoid any irreversible damage.
Use your common sense, vellum and parchment are both natural animal skins
and will readily react to other natural elements safely, when adding extremes
of heat (an unnatural element) the other elements need to be totally under
control.
Both stretched and mounted
versions of presentation are unnatural to vellum and parchment, for it assumes
an inconsistent character from the true natural look. If archivally hinged, skins should be placed
1/8" from the glazing for room to breathe, which can easily be achieved by
using multiple neutral pH window mats (this pressure against the edges of the
vellum will also minimize overall buckling.
Once framed these pieces of fine art should be hung in a dry location,
preferably out of direct sunlight. Taken
well care of, these archivally preserved masterpieces will last many future
generations.
END
For additional articles on preservation
treatment, design or mounting search your desired topic under Articles by
Subject.
If you
already know the specific title then search under Articles by Title.
Additional information on
shipping boxes is found in my book
Creative Mounting, Wrapping, And
Laminating, 2000.
The two most recent mounting
books are
The Mounting and Laminating
Handbook, Second Edition, 2002, and
The Mounting And Laminating
Handbook, Third Edition, 2008.
All books are available from Designs
Ink Publishing through this website.
Chris A Paschke, CPF GCF
Designs Ink
Designs Ink Publishing
785 Tucker Road, Suite G-183
Tehachapi, CA 93561
661.821.2188
info@designsinkart.com