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Re: Rounding and Backing with PVA



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 Duncan wrote:
>We are also using internally bonded copolymer
>PVA (Wisdom R172DT).

A very elastic and flexible PVA, which certainly makes rounding easier. I have
not seen any archival tests on it, as far as outgassing, reversibility, and long
term effects of alternating humidity and temperature conditions. I'd be
interested to know if anyone has this data.  Have you tried Wisdom R1503 for
rounding and backing?

>Backing is a separate issue all together.

The problems and solutions I indicated are in backing, not in rounding. Perhaps
I should have titled the post "Backing with PVA."

The fully glued PVA spine tends to hold the sections tightly together, and in
order to make a shoulder the sections have to separate. It becomes a particular
problem if the sewing thread is glued to the tape or cord, preventing the
section from sliding outward on the support.

Unsupported sewing does not face that particular aspect of the problem, such as
most Smythe-sewn commercial work, or chain-stitched hand-sewn books.

Commercial hardcover books are rounded only very slightly, and backed hardly at
all.  The angle of the shoulder in most trade books these days is less than 30
degrees.  That's fine for commercial case-binding, which is often done on an
in-line production machine with hot-melt adhesive.

But if a fine binding is sewn on raised cords that are laced into the boards as
in the example I provided, or laced-in tapes, one would like to have a square
shoulder so the board can sit properly in the joint. Otherwise there are
problems with the hinge. This may require movement along the sewing support of
1/8" (3mm) or more, depending on the thickness of the board and the covering
material.

Even on leather case-bindings I tend toward the 90 degree shoulder, as the
endbands look better when they come to the edge of the board and the endcap and
endband end at the same point.

One of the things I like about the strip method of PVA application, particularly
with edition work, is that it is not necessary to round and back within an hour
of gluing, or even the same day. It can be done the next year if necessary. In a
large bindery (even a "small" high quality bindery like Campbell-Logan is
relatively large) that may not be an issue, but in the one-person shop it is
often convenient to glue books up one day and round and back them another.

As an artist working in book media I have many projects going at once, and often
abandon one of my works for a long time when the inspiration for something else
strikes. There are some unfinished works in my studio that were begun in the
70's.  If I live long enough I may get back to them.
;>}

--
 Richard
 http://www.minsky.com
 http://www.centerforbookarts.org

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