Shelf Life of PVA Glue
PVA glue should be used before its expiration date. December 20, 2005
I have some questions about PVA glue. We are new to this type of glue and I am using a sample that has been sitting around the shop for a couple of years. We are doing some edgegluing of plastic laminate to plywood cores. We use a heater bar set at about 90º for ten minutes. Our heater bar has a timer switch on it so that you can walk away without worrying if the glue will overcook and crystallize. Last Friday I glued an edge and left the piece on the bar. The piece was still on the bar this morning while I pre-heated for another glueup. After the second piece was in the clamps I removed the older one.When I tested the edgebanding for adhesion, it had no stick at all. This seemed unusual because the pieces that were only heated once seemed to be really well glued.
My questions are:
1) Is there a pot life to this type of glue?
2) Will it reactivate itself if glued a second time?
3) What is a good brand to use for this purpose?
From contributor A:
PVA definitely has a pot life, and I would never use any older than one year. It's pretty cheap, so I would advise buying a fresh supply. Anything made by Franklin or Borden should work fine.
From contributor B:
PVA adhesives certainly will soften, or resoften, when heat is applied. In fact, they can soften enough to be absorbed by the wood when heated a second time, resulting in a starved joint with no strength). I have seen PVA core panels that fell apart when a veneer surface was hot laminated to the core. PVA does indeed deteriorate with time in its container, but if it is not unusual in consistency, it probably is not as badly deteriorated as you indicate. In fact, if it works for the stuff heated only once, it would seem to be fine still.
From contributor C:
Most PVA glue has a shelf life of 6 months. I'm sure that is to protect the manufacturer from any claims of problems due to shelf life. It is never a good idea to let glue sit unused for longer than that.
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