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I've been doing some resin casting for a while, and I decided to try out casting some stuff in pewter for a friend. Well, I'm running into some problems. The Alumilite RTV mold stuff I've been using isn't working, the finer details seem to get "burned" off. What do you guys use when you cast things with pewter? My google-fu is weak, all the info I've found is about the casting process itself, not mold making. Any help will be appreciated!

Have you tried lost wax casting?

Basically, cast a figure with beeswax with your current mold.

Encase it in plaster, obviously leaving a spot to pour in pewter. You also need another hole for the wax to run out of.

Pour pewter, let cool, break the plaster. You can get amazing detail work from lost wax casting.

Lonecoon wrote:Have you tried lost wax casting?

Basically, cast a figure with beeswax with your current mold.

Encase it in plaster, obviously leaving a spot to pour in pewter. You also need another hole for the wax to run out of.

Pour pewter, let cool, break the plaster. You can get amazing detail work from lost wax casting.

An excellent idea.

Also

Is the RTV silicone you are using the same as RTV-101? You say burned off? I suspect that the rubber you are suing isn't suitable for high temperature work.

I've not tried the lost wax process, it's a bit time consuming for what I want to do.

The RTV I'm using says it's suitable for metal IIRC. It's Alumilite Quickset RTV mold making rubber. But then again, it says that it's only suitable up to 400 degrees, with short durations of 500 (which is around what my melting pot heats to if I remember right)

What kind of silicon mold making "stuff" do you guys use?

I use Smooth-on products for molds/casting. Although I have never done pewter they have a product for it. http://www.smooth-on.com/gallery.php?galleryid=424

Pewter gets hot, so you need special heat resistant rubber for the moulds.

I use a heat resistant RTV for mine (that is suitable for bronze casting - pewter melts at a lower temp). I've had no issues with the rubber melting.

Both the DowCorning RTV I used to use and the current one differentiate their heat resistant ones from the others by colour. The HR ones tend to be a reddish colour.

I couldn't find any references to heat resistant rtvs in the alumilite or Smooth-on sites though. High strength, yes, but these are not the same.

RTV-101! Use it for both pewter and resin casting.

And as chromedog says, high strength and high resistance are not the same things..

I do understand the difference between heat resistance and high strength.

I'm looking at this link here that Depraved - http://www.smooth-on.com/gallery.php?galleryid=424 have any of you guys used this stuff before? Would it be suitable for casting pewter/white metal?

Mr. Burning, I found this here - http://www.tiranti.co.uk/subdivision_product_list.asp?Subcategory=51&Subdivision=173 Is that what you are talking about?

Thanks for the help guys.

Yes to both.

The smooth-on one can do 260*c and up to 316*c (and specifically mentions casting with pewter).

The other one is pretty much standard rtv-101.

I use Smooth-On Mold Max 60 for pewter casting and never had any issues with my molds (expept due to my own mistakes).

Here is where you can order it is you want. The website also has a lot of other cool stuff.
http://www.theengineerguy.com/cgi/commerce.cgi?search=action&category=BDG0