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Re: Stretching Vellum

Although vellum is hygroscopic, there are many extant examples of drummed
vellum in museums and private collections.

One of the finest pastel portraits I've restored was a late 18th century
piece on vellum, on the original stretcher bars.  Many early books have
vellum pastdowns and they have not changed the boards more than a paper
pastedown can do.  I have a pair of large (approx. 24" X 26") boards from a
17th/18th c. book which have vellum pastedowns and they remain flat.

However, I have also worked on drummed vellum (and paper for that matter)
which has split due to lack of ability to respond to extremely dry weather.

Faced with this problem, as an artist, which I am not, I believe that I
would probably paste the vellum down on something like 6-ply rag board and
line the other side with paper to balance the pull as the sandwich dried.

I would not soak the vellum in water.  What would be better would be to
make a small humidity chamber (wet blotter:fiberglass window
screening:vellum:mylar [or other impermeable membrane]) and leave the
vellum there until it is limp.

Then I would paste it out with a thin layer of a thick, cooked wheat starch
paste, and work if down on the board with as little stretching as possible
to keep it smooth.  Same thing goes for the paper on the other side.

Depending on my feeling about the vellum at the time, I might warm up some
hide glue and blend some wheat starch paste into that and use the
combination as the adhesive.  In this case, the glue would be just warm
enough to be runny, but not hot, and I would work quickly.  But gently....

One of the tricky things about doing something like this is that the vellum
may be fairly thick & stiff in one area and quite thin in another (for
instance, a large piece cut from the middle of the spine out to the belly).
A piece like that would not be a very good candidate for hinging,
drumming, or mounting.

I would also let everything dry for a week or more under gentle pressure,
changing blotters, etc.  Every now and then I would leave it laying on the
bench to air dry.  When it bagan to curl up at the edges, I would turn it
over and let it equalize, then return it between dry blotters and pressure.

Good luck.

Jack C. Thompson
Thompson Conservation Laboratory
7549 N. Fenwick
Portland, OR  97217
503/735-3942 (voice/fax)


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