Metal Casting Token/Coin

[DeepDenizen]

Ok I need some help.

My nephew has a club with some friends and they drew a sort of emblem for it. He asked me to make it into a coin/token so I modelled it in wax, used some rtv silicone to make a 2 part mold and then used polyester resin to cast it. It came out really well, the design is there. The problem is they were a bit light and looked cheap. So then I bought some bronze powder, recast with a clear resin and after some attention with wire wool they looked very nice and my nephew was happy.

However I decided to try casting them with metal as I've always been interested in metal casting. I bought some pewter and high temperature silicone. I used the first resin coin to cast a second 2 part mold. I did the casting and found a problem. The entire surface of the coin was covered in big pock marks, lots of deep holes, some small holes, none of the pattern can be seen it's so bad. Although the snake I cut into the edge of the token came out really well.

So I tried again, I cut a channel for air to escape but the same problem happened. So I cut several holes for air to escape but still the same problem.

Can anyone advise me? I don't really need to do this, my nephew and his friends are happy with the resin ones but this is just annoying me. And I thought I might try some kind of figurine as well, but I want to get this sorted first.

Thanks guys.

 

[Exxos]

Four questions.

- Is the silicone graded for this level of heat and the reaction?
- Did you pre-heat your mold?
- Did you talc the mold?
- Did you make sure the metal was evenly heated, not just molten?

When I cast parts for RPG and wargames miniatures, I always warm up the mold and talc it. The last time I had bad pocks was the result of the mold leeching out something and when it hit the hot metal, it formed bubbles of gas. I also let the molten metal heat a few minutes past the molten point, swirling it in the crucible now and then, to make sure it is evenly heated so I don't get weak spots.

 

[DeepDenizen]

The silicone is graded for pewter and lead casting.

I did pre heat the mold, but I have to do it at a lower temperature (around 100 C).

I did not talc the mold, I will try that next, could you explain the purpose of this?

I tried heating the metal further and swilled it around. I gave it a few tries in case I did something wrong so I tried just heating it until molten or heating it for ages, neither made much difference.

 

[greylocke]

When I did Tin Soldiers, the talc had 2 functions according to the instructions that came with the kit. #1 to insure the metal can be removed from the mold after it cools and #2 it allowed the metal to flow over the mold easier allowing the metal to fully coat the details. Just be sure the talc you are using is VERY dry. If it's damp it will release the moisture as steam which will give you a bad cast.

 

[DeepDenizen]

A big thank you to Exxos. I tried the casting againt today and added the talc, the casting came out perfectly. I actually couldn't believe that something as simple as a light dusting of talc could make such a difference. I only wanted 1 token just to try it but I made a second and third just to confirm this was the problem I had been having all along. Second cast came out great, all the detail showed. I cleaned the talc off the mold and cast again, the terrible pitting and big pockets returned.

So yeah, thank you very much. I'll try a figurine next when I have the time to carve it out of wax. Need to pick something good. And I'll have to remember to account for the slight shrinkage.

 

[DeepDenizen]

Greylocke

Thanks for the information.

 

[kontrolr]

can anyone recommend a technique for casting aluminum coins besides lost wax method or soapstone