Repairing parchment with collagen

I'd like to thank Chris Woods for his excellent exposition of the
properties of collagen (however constituted or reconstituted) and
adhesives.

One use of isinglass which he mentions (...by brewers who use the
material ground up to clarify beer [and wine]) should be amplified,
before people race out to their local home-brew supply house to
purchase packets of ground isinglass.  To retard spoilage, isinglass
prepared for brewers is treated with sulfurous acid (H2SO3).

F. Dawidowsky, in A Practical Treatise on the Raw Materials and
Fabrication of Glue... (Wm. t. Brannt, trans.) published by Henry
Carey Baird/Philadelphia, 1884, mentions that inferior grades of
isinglass are bleached with sulfurous acid.

Walter J. Sykes & Arthur R. Ling, in The Principles and Practice of
Brewing, published by Charles Griffin and Co., Ltd./London, 1907,
discusses the use of acetic, tartaric, and sulfurous acid to
manufacture "finings" from isinglass.

Paul I. Smith, in Glue and Gelatine, published by Chemical
Publishing Co., Inc./ Brooklyn, 1943, repeats this information and
gives a listing of solution times for a dozen samples of isinglass.

Newer books on home brewing discuss the use of isinglass to fine
beer or wine, but those on my shelves do not mention sulfurous acid
being used in its production.

Jack C. Thompson
Thompson Conservation Laboratory
7549 N. Fenwick
Portland, OR  97217
503-735-3942

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                  Conservation DistList Instance 10:90
                  Distributed: Tuesday, April 22, 1997
                       Message Id: cdl-10-90-001
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