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Re: Plywood boards

>I'm under the impression that plywood lets off a gas which is harmful to
>leather and paper. Is there an authoritative opinion on that?

>Yehuda Miklaf

About 15 years ago some students in a bookbinding workshop in my
lab wanted to make medieval-style bindings.  Since I didn't want
to use some of the air-dried oak from my stash I purchased some
birch plywood from a local hobby shop for them.

Tonight I looked at the blank book I bound as a demonstration,
and the endsheets are acid burned.

However, the acid burning is not consistent.  The front endsheet
was not pasted down, but it is burned except where the vellum
slip on the inside of the board protected the paper (it was
a split sewing support of laminated alum tawed pigskin and calf
vellum [Gary Frost's design]).

The back endsheet was only pasted half-way toward the fore edge
from the joint.  Just beyond the point where the sheet was
pasted there is a spot where some paste got on the board and
was wiped off.  Enough paste remained in the wood to create
a 'picture' of itself.

With regard to wooden boards used in books during the middle
ages and renaissance, some have 'burned' their endsheets,
and some have not; in fact, most have not.

My personal opinion about why this is so is that properly aged
wood does not outgas as badly as newly processed wood.

On average, it takes about a year-per-inch to air dry wood and
that is a very rough rule-of-thumb.  I have split a quarter of
oak which has been laying around the lab for at least a dozen
years and it still felt slightly damp inside and there was a
clear odor of acetic acid (vinegar).

The boards I prepare for use in restoring early books are worked
down to approximate thickness over a period of 6-8 years.  When
I bring them down to their final thickness I work only on the
side which will take the leather; the side which will take the
pastedown is already finished and has been finished for a year
or more.

I have been experimenting with the idea of boiling the wood (to
remove tannins and sap, etc.) but that test has only been going
on for about 6 years and I'm not prepared to say one way or the
other at this time.


Jack C. Thompson
Thompson Conservation Lab.
7549 N. Fenwick
Portland, Oregon
USA  97217

(503)735-3942 (voice/fax)


"The lyf so short; the craft so long to lerne"
Chaucer, <The Parlement of Foules> 1386 A.D.

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