Hydrogen peroxide as cleaning agent

Daniel-Harry Steward <posterdoctor [at] msn__com> writes

>I use a solution of hydrogen peroxide to clean paper surfaces.  The
>paper is usually printed posters and the inks are not affected by
>the cleaning wash.  I have done numerous tests and the papers appear
>to have no residual damage from the peroxide solution.  Does anyone
have other input with this procedure.

Hydrogen peroxide is not a "cleaning agent," it is a *bleach*.  It
chemically oxidizes chromophores in the paper, changing them to
*acids*.  Raising the pH of hydrogen peroxide solution may favor the
creation of ions, rather than free radicals, but no paper
conservator would deny that damaging free radical chain reactions
can occur.  This is why bleaching may continue overnight, hours
after the treatment has stopped. Rinsing with a fresh bath of
calcium hydroxide at pH 8-9 and testing the rinse water with a
peroxide indicator strip will allow you to ensure that the peroxides
are no longer reacting in the paper.  Neutralizing the bleach with a
reducing agent is possibly more effective, and I know that there are
several conservators who have tried oxidizing/reducing combinations
with good results.

Let me add that light bleaching, which is a milder form of peroxide
bleaching also generates a lot of acids.  A light bleaching bath
with calcium hydroxide dropped from pH 8 to pH 5 in four hours under
a UV-filtered light bank in our lab.

Valinda Carroll
Colonial Williamsburg Foundation


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                  Conservation DistList Instance 16:4
                  Distributed: Wednesday, July 3, 2002
                        Message Id: cdl-16-4-003
                                  ***