On Tue, 23 Nov 2004 14:37:59 -0600, George
wrote:

jim rozen wrote:

In article , Bob Edwards says...

Now I won't sonic-clean anything but glass lenses again. Damn!

Yep. I've dunked my glass lenses in the ultrasonic at work many
times, because it does a great job of de-greasing them. But
I did find that the polycarbonate lenses developed a fine pattern
of crazes, or cracks, on their surface after a few times of
doing that. Now I only use hot water and soap on them.

Jim

Sounds like you have a chlorinated hydrocarbon in the tank. It doesn't
take much to craze polycarbonate. Just the residue from cleaning oily
parts would be enough.

I remember a particularly interesting case of a SCUBA diver who died
as a result of lubricating the O-rings in the air regulator with a
silicone grease. The regulator was made from PC. The regulator was 5X
over designed for its intended application. The grease reduced its
strength to virtually nil.

BTW Jim, if those were safety glasses, they are no longer very safe.
The crazes will propagate under any tensile load.
Since silicone grease is the standard grease for scuba divers and
their gear it makes me wonder how true this story is. You'd think that
a company making life support equipment would try all ways possible to
make the unit fail. I'm assuming that it was the second stage reg.
The first stage regulator, with hoses screwed into it, and supporting
all the tugs on the hoses, and being exposed to 3000,00 psi
potentially would seem to be a bad choice for polycarbonate. Brass
works so much better. And if it was the second stage, a free flowing
hose can be used for breathing. In fact, scuba divers must show the
ability to do this to be certified. Please giuve us some more facts.
ERS