[FT]Mold probs(Was Scratchbuilding questions)

3 posts · Sep 22 2001 to Sep 25 2001

From: Alderfek@a...

Date: Sat, 22 Sep 2001 10:04:33 EDT

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

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

From: -MWS- <Hauptman@c...>

Date: Sat, 22 Sep 2001 10:43:13 -0700

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

> At 10:04 AM 9/22/01 -0400, Alderfek@aol.com wrote:

> 1-to-1 RTV material sold by micro-mark.

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.

From: Tony Francis <tony.francis@k...>

Date: Tue, 25 Sep 2001 12:02:02 +0100

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

> -MWS- wrote:
One of
> > my molds started to "sweat" so that the more I used that mold, the

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.