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Re: About bleach; Ms. Woods comments



I will not undertake to discuss bleaches and non-paper fabrics as I know so
little about them; I suspect that paper and cloth, when both are of cellulose
content, will yet offer somewhat different problems and solutions, if only
because of gross structural differences and methods of manufacture. Can't
toss my text block in the washing machine.
For those coming late to this discussion, I know of no one who would suggest
the chemical bleaching of paper by any method whatsoever without very
carefully thinking out one's reasons, using it as a very last resort, and
under constant observation and very carefully controlled conditions, most
particularly the monitoring of pH levels in the working solutions as a guide
to process.
For my comments on the use of sodium and chlorine hypochlorites and dilute
acetic acid (vinegar) in paper bleaching, I rely largely on the work of
Margaret Hey at the Library of Congress (in print, amongst other
publications, in The Paper Conservator Vol. 2, pg. 10-23, specifically pg. 16
) and my own working experience. I will very greatly appreciate being
directed to the work which has countervened Ms. Hey's.
While it is certainly true that sodium metabisulphate (which in solution
reacts as a weak acid) can be used to break down residual hypochlorites, and
that both it and the byproducts of the hypochlorite destruction are readily
washed out of paper, it's disadvantage is that it is a sodium salt. One
prefers to avoid the use of sodium salts in paper conservation if at all
possible, and again citing Hey (herself citing work going back to Bonnardot,
1847) dilute acetic acid will do the job, in concentrations and for exposure
times low enough (following the after bleach washing, a 5 minute immersion in
a 5% acetic acid solution, followed by washing in water until the effluent no
longer tests acidic) that it's risks are less than those involved in the use
of sodium salts. Again, the final deacidification and buffering of the
bleached paper neutralizes any possible remaining acid.
All best
James


James Tapley Hand Bookbinder
2077 Thirteenth Street
Sarasota, Florida
34237   USA

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