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Re: [BKARTS] PVA, internally plasticized



An issue which I don't believe has yet been mentioned in regard to the 
quality of PVAs is that of "plasticizers."   

While this information may be somewhat dated, it was the case that the PVAs 
sold by conservation suppliers were "internally plasticized," meaning that 
their flexible qualities were molecularly locked in.   

This is compared to non-internally plasticized PVAs which loose their 
flexibility over time, sometimes rather quickly.   An everyday example of this 
phenomenon, as described by the late Paul Banks, would be a plastic shower curtain, 
completely flexible when purchased, but that over time, looses is flexibility 
and cracks as the non-internally plasticized components evaporate.   

This is especially important for adhesive bound books, but is certainly 
significant for sewn bindings when the use of PVA is appropriate.

The formulas of commercial adhesives may change without notice, but perhaps a 
current spec sheet or correspondence with the manufacturer may identify 
which, if any, adhesives they make are internally plasticized.   Formulas, 
themselves, are not usually provided.

Hope this is helpful.   I am interested in any updated information anyone may 
have one the subject.   Thanks.

Nancy
Elkins Park, PA

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