Photocopy adhered to plastic film

Chantal Schwendener <chantal.schwendener [at] slb__admin__ch> writes

>A fusion between the toner lines of a photocopy and the plastic
>pocket (obviously not polyester) it is enclosed in, seems to be
>caused by the migration of the plasticiser contained in the plastic
>film. This adhesion doesn't allow us to remove the photocopies from
>the pockets without damaging the toner lines. Has anybody been
>confronted to this type of problem and developed expertise to deal
>with it (e.g. heat, cold, solvent)?

I am not clear whether the photocopy is on plastic or paper. The
pocket is most likely plasticized PVC (you could test it using a
copper wire burning test and looking for a bright green flame).  The
phthalate plasticizer in the pocket (usually about 30% by weight)
has diffused into the photocopy, dissolving and transporting its
ink.

I have seen this phenomenon many times and tried both cold and
solvent treatments to reverse it. I doubt that any treatment
including cooling or solvent, can  reverse the migration of the ink.

As for removing the photocopy, if it is on plastic, you may be able
to it by cooling the whole enclosed in a polyethylene bag in in a
freezer and physically separating the two components while they are
brittle (the Tg of the pocket is probably around  20 deg. C, so it
will be in a glassy phase in a domestic freezer).  If the pocket is
unimportant, you could cut it to remove the photocopy. If you want
to save the information on the photocopy, you could photocopy the
whole pocket with a white paper as background.

Yvonne Shashoua
Senior Researcher in Modern Materials
Department of Conservation
National Museum of Denmark


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                  Conservation DistList Instance 19:36
                Distributed: Wednesday, February 8, 2006
                       Message Id: cdl-19-36-004
                                  ***