casting replacement camera/viewer parts

[E R Swanson <ers@xxxxxxxxxxxxxxxxxxxx>]

I went through the alumilite site Tom had mentioned (www.alumilite.com)
and their product range has expanded since I last looked. It's still one
of the most expensive products, but it has the advantage of being
available in small amounts. Also, they're selling urethene coloring
agents, which could be very useful, but until you actually see how it
looks as a casting, probably best not to count on the color. They also
claim the rtv they sell doesn't need deairing, and this is probably true
for light mold use. The reason you should deair all rtv rubber is that it
makes for a sturdier more durable mold, but if you only need to make one
or two parts, it should be fine w/o the vacuum.

Mold pattern making is something of an art if you're making a two or three
part rubber mold (sometimes necessary to go three or more part to deal
with undercuts), and there are a lot of tricks for putting channels in the
mold so the resin reaches all parts and doesn't leave you with air bubbles
in the finished part. There is a special channel making wax used during
the mold building part of the process, though you can also carve surface
channels.

Lastly I saw the alumilite now sells an rtv molding putty, which would be
handy for small parts that used a simple one part pour mold. 

When you buy any of this stuff, ask for the MSDS (Manufacturer Safety Data
Sheets) for all the products. Neoprene gloves are also a good idea.

Elliott