Glassine

Lauren Jones <collectionscare [at] rhqre__co__uk> writes

>...  I have read recently that glassine could be used as a
>slip sheet for between prints and drawings (Margaret Holben Ellis'
>Care of Prints and Drawings).  But when I mentioned this to a
>visiting conservator, she was a bit dubious about its use.  So, can
>anyone confirm the good or bad points of using glassine, I have now
>purchased a huge roll, at some expense, from Preservation Equip Ltd
>UK who pitch it as "transparent, smooth with a pH of 7.0,
>unbuffered..."

My understanding is that, technically, glassine consists of
cellulose fibres highly fibrillated to a semi gelatinous state, made
into paper which is then heavily calendered until it forms a
translucent sheet. The point is that it is not parchment
paper/vegetable parchment but a product of normal papermaking
technology.

The hesitation conservators have with glassine relates to the
tendency of older glassine paper to discolour heavily and to
visually alter the emulsion/ image layer of photographic negatives
where a paper seam of a glassine sleeve contacts the emulsion.

Older glassine was not standardised. There was no industry wide
control over manufacturing impurities or the cellulose source, and
it was thought to have had various substances such as glycerine,
oils or waxes added to increase its transparency. I have also
wondered if the fibrillation did not expose the micro fibres to a
greater degree of natural oxidation than with the thicker fibres of
normal paper.

I have quantities of glassine purchased as conservation grade almost
30 years ago which has not discoloured either in use or storage. I
hesitate to use it often because of its reputation, while its
transparency and smoothness are very useful qualities.

I think you might be able to resolve your issue by making an enquiry
of the manufacturer/supplier if, as a neutral pH material, it has
passed the PAT photographic activity test. If it has, it is unlikely
to pose any threat to prints and drawings.

James Elwing
Conservator of archival material
Elwing and Gurney Archival
Lawson, Australia


                                  ***
                  Conservation DistList Instance 26:51
                   Distributed: Tuesday, May 28, 2013
                       Message Id: cdl-26-51-003
                                  ***