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Making Bad Molds

I switched to Akron Jewelry Rubber by Zero-D Products several years
ago. You will never have a problem with any of their mold rubber
products. I have tried the Rio rubber made in Mexico. It stuck to my
brass sprue formers. Also, there was only about 4 pounds of rubber in
what looks like a five pound box. They sell by strip count instead of
by the pound. I think they sell 15 strips to a box, which turned out
to weigh only about 4 pounds. That seems a little devious to me.

Craig M.

Somehow this post got turned around, making it sound like I was
unhappy with Castaldo rubber. This is not the case. It was the
Mexican rubber from Rio Grande that has caused all the sticky
problems. It is not a silicone rubber, just very messy to work
with. I am glad that the box of it is finally used up. I just wanted
to try it because it was new…big mistake!

I’ve never had a problem with Castaldo vulcanizing rubber.

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concern over washing frames with solvent is a bit over done, as some
folks have noticed. If you are using the high quality silicones
based in modern chemistry, such as the 4X Series of silicones from
Zero-D Products, you have little to be concerned about. Occasional
washing with soapy water is appropriate, just as you should, from
time to time, clean all of your lab tools.

The lower cost, low quality silicones that are still based in older
chemistry do require great care when changing over to natural
rubber. In many cases, solvents may be needed, as these silicones
leave ingredients on mold plates, etc. The cure process is not
always complete. Generally, you can see the remnant on the mold

Do not confuse the foregoing with the need to clean tools used with
the liquid RTV silicones. In particular, if you use any urethane
RTVs, clean up well at the point of change over to silicone RTV.

Call me if you have questions or wish to evaluate the 4X series of

Bill Mull
Zero-D Products, Inc.
Precision engineered materials solutions
Toll free 800-382-3271 in USA, Mexico and Canada
Phone 440-942-1150
Fax 440-942-2130