Polyvinyl acetate and offgassing

Alexandra Greathead <mcard.pro.kew<-a t->gtnet< . >gov< . >uk> writes

>I am in the process of making boxes in which rolls of 35mm negative
>film strips will be stored.  I am using PVA in the process of making
>the boxes and am wondering what the consensus of opinion is
>regarding the length of time the boxes should be left open and
>unused until offgassing no longer occurs.

The first question is whether the material in question is PVAc resin
or an emulsion (the proper word is probably dispersion, but we're
all used to calling it an emulsion) and if the latter, whether you
are using it wet or as a heat-seal.

PVAc resins have a rather long solvent retention time for some
solvents; but the solvents can be adjusted for allow for this. If
the material is an emulsion, then there is no definitive answer. Test
of emulsions reported in the conservation literature make it
clear that these materials vary widely and that pH in particular
ranges from near 3 to near 9 in the liquid state and can change
during drying. Since pH may be crucial as to the potential affects
of off-gassing on material in the boxes, an emulsion should be
chosen carefully. As to your actual question--I would be interested
in hearing what common practice is, but I don't believe that answer
can come from present research data.

                                  ***
                  Conservation DistList Instance 11:13
                  Distributed: Friday, August 1, 1997
                       Message Id: cdl-11-13-006
                                  ***