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I have long been an advocate of GE II silicone for
mounting telescope optics, and I have never had a problem with it... until
today.
I suspected something was wrong because it was very
difficult to squeeze out of the tube as if partially cured, and because it did
not have the usual acetic acid smell. The goop did not cure at
all.
I checked the label on the tube, and it referred to
a barely legible expiration date for the material. The expiration date was
October, 2000. It is now August 2001, so the stuff is ten months out
of date.
So, when using silicone, check...
(1) the expiration date pressed into the base of
the tube,
(2) the stuff easily squeezes out of the tube,
(3) there must be a smell of acetic
acid.
As usual, make sure all surfaces to be bonded are
grease-free by cleaning them with acetone; smear a thin layer onto each surface
with your finger before final assembly.
. . . Richard
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