Re: [FT]Mold probs(Was Scratchbuilding questions)

-MWS- wrote:
> 
> At 10:04 AM 9/22/01 -0400, Alderfek@aol.com wrote:
> >Hi all,
> >   Well, I started to pour lead last night and ran into a problem.
One of
> > my molds started to "sweat" so that the more I used that mold, the
> > castings come out worse and worse. Any ideas on how to fix ? Could I
just
> > bake it out in a oven ? The mold itself I am going to have to redo
but if
> > I have this problem again I will need a fix. The mold is made from
the
> > 1-to-1 RTV material sold by micro-mark.
> >
> >Thanks,
> >Kirk
> 
> You'll probably get a better answer over on the [casting] list, but
from
> personal experience I can state that Micromark's 1-1 RTV is really
designed
> for use in resin casting, not whitemetal, and it will only withstand
> limited runs from a low temp metal pour before burning out.  If you
want to
> cast in white metal, you really need to switch to vulcanized molds
instead
> of RTV ones.

You _can_ cast metal quite happily in RTV moulds - you just need the
right RTV. We use RTV-101 in our centrifuge, a pretty tough red-brown
rubber which is good up to 316ºC. I've also used RTV-11 (white, much
softer) for small-run hand moulds.

Tony

-----------------------------
Tony Francis
Senior Software Engineer