I had a plastic bottle of yellow wood glue that had sat at room
temperature 25 years. When I needed it, the level had gone down and it
was too thick and stringy to stick properly. Over a period of days, I
added water and stirred with a screwdriver.
It worked for the job I was doing. The other day I read that wood glue
goes bad after a few months. Is my old wood glue defective?
Problem is the plastic bottle. Over time, water will permeate out and
glue will dry out. I've recovered old glues by rehydrating but since
these glues are emulsions, they do not completely recover. Like you
advise, I'd only use for trivial things.
You've made me curious. Dow doesn't specify shelf life for polyvinyl
acetate but says it's shipped with a chemical to inhibit polymerization,
and it should be kept out of sunlight and below 86F to avoid it.
Dow says polymerization can burst containers. A page on wood adhesives
says PVA glues should not be used on joints with a lot of shear because
in time the glue allows creeping. It doesn't say the bond gets weaker.
The Elmer's page says the glue hardens by drying and the shelf life of
classroom glues is two years. A difference between a solution and an
emulsion is that you must apply energy to make an emulsion. If you can
mix in enough water to make the glue thin enough to adhere, why
shouldn't it be as good as new?
I remember reconstituting PVA glues three times. The first two times
were to replace foam surrounds on loudspeakers, using glue left over
from working on other speakers a couple of years earlier. It was a
critical application. I used reconstituted glue for eight surrounds.
As far as I could tell, it worked like new glue.
I've read that manufacturers of expensive speakers have used urethane
although it would rot, because other foams didn't sound as good. One
manufacturer used urethane with a butyl face.
I've read that the surrounds of speakers made in the last 20 years or so
hold up better. I don't know if it's because of additives or a
different kind of foam.
My first time, I bought expensive kits for four woofers. One repaired
woofer failed my listening test. The glue had been drying several
hours, but I managed to cut it without damaging the foam. Whew!
I got my last ones from matelectronics.com. It seemed risky because
they weren't completely described. I bought four sizes and they all
worked. I'd call it better foam than the ones I bought before for ten
or twenty times the price, but I'm not qualified to judge foam.
I was doing a project and grabbed for my bottle of glue and it had
thickened up quite a bit even though the top was on.Wife says its at
least 5 years old. I added a little water and warmed it in the
microwave for a few seconds. Worked fine, I still bought a new bottle
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