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Re: [BKARTS] PVA;: what Elmer's is that?

I whole-heartedly agree with your comments about adhesives, especially with the accelerated aging at 100 degrees.
For many years, I have been trying to suggest that we prepare test pieces, keep them around the shop and look at them regularly. At the same time, I feel it is important that we go back and look at the work that has been done to access how well things are holding up in REAL LIFE. This certainly is easier for our fellow conservators who work in libraries where they can walk out into the stacks and look at their work; its a little harder for those of us in private practice (independent binders/conservators). The response that I hear from various colleagues is that they do not take the time to look at their earlier work. We could learn a lot from the occasional examination of earlier work where we/they know what materials were used.
I have some samples of PVA mixtures (Jade 403 with wheat paste and methyl cellulose) that are now 25 years old. During one of the early GBW Standards conferences, we heard the experts say that mixing adhesives is a bad thing to do because the adhesive could fail all of a sudden after many years. I have not seen any failure, and I hope that nothing happens, as I have been using the same mix for all these years.
I also have some polyester film encapsulation test samples from Elaine Schlefer that are now 22 years old. The samples provide a good insight into the changes that are occurring --- but that is another story.
Bill Minter

On Feb 3, 2006, at 12:06 PM, Bruce Levy wrote:

To my knowledge, PVA acidity is quite different when it is wet and when it's dry. One needs to be careful about throwing data around without pointing out the criteria for collecting such data. If "conservation" PVA is significantly less acidic (maybe a buffer was added like calcium carbonate- I have no idea) how does that effect it's adhesive properties eg. does it hold as long, better, worse? What happens when it "crosslinks", does it just crumble into white powder? Has anyone done a dry test from the various PVA's-especially with the improved PVA's produced in the last 15-20 years? Oh yes, also, the archival tests. What about the possibility that 100 degrees for so much time might not really be a fair comparison TO REAL LIFE AND TIME?

William Minter Bookbinding & Conservation, Inc. 4364 Woodbury Pike Woodbury, PA 16695 814-793-4020 Fax: 814-793-4045 Email: wminter@xxxxxxxxxxxxxx

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