Subject: Re: Silicone Rubber Mold Making

From: [email-masked] (Don Stauffer)
Date: 18 Jun 1996 07:50:10 CDT

In article <[email-masked]>, Larry Ludwick <[email-masked]> 
says:
>
>Does anyone on the group have experience making molds suitable
>for low temperature metals such as tin, lead, and pewter.  I 
>was steered toward Dow Corning's Silastic -- only to find there
>are about twenty different types of silastic.
>
>I am looking for a relatively simple, room temperature vulcanizing,
>silicon rubber material for making molds for pewter items.
>
>Any help appreciated,
>
>Larry

I use silicone materials sold to the model building community.  It is 
repackaged so it does not necessarily have the original manufacturer's 
type number on it.  I have used two sources; Ace Resin (don't have their 
address handy) and BareMetal. The later has a web site, do a search on 
the name.

I have used the Ace compound extensively.  It pours with very high 
viscosity, but settles well.  Also has limited shelf life.  I have just 
bought the new stuff from BareMetal.  It is supposed to have low 
viscosity.  Hope to try it this coming weekend.

Also, I have used Plaster of Paris for parts which do not have extensive 
fine detail, and no undercutting.
Don Stauffer in Minneapolis
[email-masked]

---

From: [email-masked] (Barry Workman)
Date: Tue, 25 Jun 1996 07:14:11 GMT

[email-masked] (Edward Haas) writes:

>	--Go to a jewelry supply house and get some stuff called "grey 
>tuffy"; they usually want you to bring your own containters, too. There 
>is a white goo and a transparent goo that have to be mixed in some ration 
>or other, not too hard to figure out, and it cures in 12 hours or so. The 
>trick to getting good quality moulds out of this stuff is to put it in a 
>bell jar and draw a good vacuum on the stuff, after you have mixed it, 
>before you pour it onto the form to be copied; this removes many bubbles 
>and reduces the possibility of a void forming at the boundary between goo 
>and part.
>-- 
>	"Steamboat Ed" Haas	:	When fortune proves elusive, 	
>	COMING SOON		:	Concentrate on fame...
>	http://www.west.net/~steamer  	
>		---Decks a-wash in a sea of words---
>	

(Uh, hi, Ed.  How's the new firebox comming?)
In my youthful existance, I sold jewelry supplies for Bourget Bros.
In Santa Monica, CA.  At that time there was a silicon RTV system 
available.  It came in two quart cans with a molding frame and
all.  It was designed for making wax injection molds for jewelry,
of course.  The nice part about it was it was a clear RTV stuff so
you could see if you had any bubbles in the mold before it cured.
Curing time was in the 4 to 8 hour range as I recall and we could
get the bubbles out on a vibrating table.

The bell jar and vacuum is a good method to debubblize most things
however, you usually end up with a lot of goop on the inside of the
bell jar and they ain't cheap.  We used to use old (and I mean old)
reefer compressors to pull the vacuum -- if you come across an old
('50s) fridge that is being disposed of, pull the compressor -- it's
worth the time.
-- 
    - Barry Workman