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J. Clarke
 
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Default Shelf life for glue (revisited)

George E. Cawthon wrote:



Leon wrote:

Storage conditions will factor in with each set of circumstances.
As for your 18 year old glue, it is too early to tell if it is still OK
or
not. You may have tested it by doing a glue up and it appears fine but
glue
deteriorates over time any you test piece may not hold up. It could
possibly fail in 10 years. Glue is CHEAP and it should hold your
projects together long after you are gone.


I have Weldwood Plastic Resin glue, Elmer's carepenter's glue, and
Elmer's resorcinol glue that are old. None give a shelf life on the
container. I think I saw 1 year for Plastic resin (a powder).


The data sheet says "1 year minimum" whatever that means. What's the
maximum I wonder?

In any
case, all have been used long after they were purchased and continue
to performed as expected. There is no reason to believe that glue
will fail some time after the application if it doesn't fail
immediately after or during application. All glues probably fail over
a period of time and under adverse conditions.


Kermit Weeks flew his deHavilland Mosquito to Oshkosh, Wisconsin in 1990 to
be put on display in the EAA museum. It was more than 50 years old at the
time, and if you contact the EAA museum they'll likely tell you that if
it's not currently flight-ready the glue is not the reason. If glue will
hold a combat aircraft together for over 50 years then that "period of
time" is long enough that I'm not going to worry about it and you don't get
conditions much more adverse than a WWII bomber experienced.

The world is so full of crap about products and applications that it
is difficult to know what is true, but some is such obvious bull****
that you wonder why people believe it. As an example, periodic wheel
alignment. Wheels are either aligned or not, and the only way to
become unaligned is to bend, break, or wear out a part. If you don't
need a new part for the alignment then you didn't need an alignment or
more likely it wasn't aligned correctly the last time.

Because some things do need periodic maintenance and some things do go
bad after a period of storage, it is easy for manufactures to prey on
the gullible by insisting on certain periodic maintenance and on
replacing older products.

A 1 year or six month warranty (or shelf life) is probably more about
legal protection and a desire to sell more product than any truth
about the product.


Really depends on the product and also on what you're doing with it. Would
you want to fly in an airplane that had been stuck together with out of
date adhesives? Would you want a surgeon to stick your body parts together
with out of date adhesives (surgeons do use adhesives, usually some variant
of superglue, instead of sutures or staples in some situations these days).

A while back I did some preliminary testing on a group of coatings,
attempting to select one to be used in a high-wear area on military
aircraft--we had in some cases to buy several gallons to get the quart or
so we needed for our tests. Once purchased the stuff was carefully stored
according to the manufacturer's instructions and if there were no
instructions it was kept refrigerated. That project got put on the back
burner for a while, then got hot again a couple of years later, when I got
a budget to do a full evaluation of one of the coatings. We pulled out
the samples we had and the first thing we did was replicate the preliminary
test. Results were _very_ different. The stuff looked the same in the
can, and seemed to spray the same, but when we started doing measurements
we found that we didn't get as much build per coat, the color was slightly
different, and the durability of the cured coating was _much_ less. This
is stuff that nobody would have noticed if we hadn't been doing tests with
instruments and comparing with previous data--if we had just sprayed the
stuff and put it in service we would never have known there was a problem
until it wore out prematurely. Tried it again from different cans that had
never been opened before. Same result. Checked the shelf life and
according to the data sheet it was 6 months. So we called up the
manufacturer and got some fresh sent out and the properties on that were
what they were supposed to be.

So don't assume because a glue _seems_ to be OK that it _is_ OK. It might
be or it might not. If failure of the joint could result in somebody
getting hurt or in significant property damage then use fresh. If the cost
of failure is small then take chances.

--
--John
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(was jclarke at eye bee em dot net)