Metal Casting Zone

Hi guys. im still sourcing all my equipment to get started, got most of it now, but wondered about releasing agent.

i was going to buy Cilchem aerosol releasing agent which seemed to be exactly what i needed, but because its a hazardous aerosol, noone will ship it to me to the shetland isles, and for a £5 tin the only way of getting it to me was going to cost atleast £20 whivh seemed rediculous.

is there anything else i can use as a releasing agent for silicone moulds? either something i can find locally, or something i can order which isnt aerosol and therefor can be posted?

Shouldn't be a problem. But first one needs to figure out the goals. Are you trying to get a fairly smooth finish. How hot will the metal get. Do you have access to a pressure pot? Also is this organic rubber or regular synthetic RTV?

I am new to metal casting myself but will drop a couple points that may be of use.

For instance RTV can be dusted with talc, (baby powder has been used in a pinch but there is fragrance and colorant added to it so that is not quite as pure as the mineral talc by its self,) the excess talc is blown off and then you cast. I believe the organic rubbers are often treated the same way. Often they pour talc into an old sock and hit the mold with the sock to get a fast coating.

The David in the lower left is a simple gravity pour with no lubricant. The David on the lower right is with brushing a coat of fine talc into the mold first and then blowing it out with a few gust from my mouth. Then simply gravity poured with no pressure added. Note that there is a slight dimpling from the talc or mica or graphite (they are alternative release agents.) I have a spray graphite on order and look forward to trying that for my gravity pours. And the rubber mold is made of Rebound-25 RTV silicon rubber. The metal is 281 from Rotometals. In all sceneries I am getting my best results from this metal. (58% bismuth + 42% tin)

The two Davids above had been poured and quickly placed into a pressure pot with zero lubricant or release agent. The top left only hand polished with a paper towel across the flats with little effect. the upper right David is hand polished with Vigor rouge white "Wonder" peal away compound and a microfiber eyeglass polishing cloth.

I'll follow this thread to see if anybody else chimes in or you have any questions.

Blobber

Hi Jarveye
When you mention mould release,are you talking release from rubber mould and metal casting or are you wanting the release agent to seperate silicone rubber from silicone rubber when making a 2 part mould. Blobber is right to suggest powder on the mould for pewter casting. If it is for rubber to rubber contact vasaline is good to smear over the lower half of a mould before pouring the 2nd half. Works for my RTV moulds.

Hi, yes i would like a) make a 2 part mould and make sure that both silicone parts dont stick together, and b) make sure the pewter doesnt stick or react with the silicone... ill need to check my details on the exact type of RTV silicone and pewter

OK, Johncast nails the rubber to rubber seperation. Vaseline works great for parting lines, never fails and goes a loooooong way.

Also a thin coat on ones hands and feet before slumber prevents scaley hands and dead skin along the heals. Oops...showing my age.