Hard Rubber Mold? Any Ideas?

Question

I have a friend that is making pouring lead peices and has a need to build his own custom molds to do this with. He has had one made for him that is made out of hard rubber (like a tire) its 2 peices. He was told that its a special kind of rubber and u take the part you want to make and force the two peices together for a set amount of time , then you take apart and cut pouring holes to pour the lead through. Any ideas of the materials to do this with and instructions? Or any other ideas to do this with. Making fishing lures.

tomcas · Accepted Answer

Most people use the two part RTVs (silicone) from GE or Dow.

carl mciver · Answer

| I have a friend that is making pouring lead peices and has a need to| build his own custom molds to do this with. He has had one made for him| that is made out of hard rubber (like a tire) its 2 peices. He was told| that its a special kind of rubber and u take the part you want to make| and force the two peices together for a set amount of time , then you| take apart and cut pouring holes to pour the lead through.   Any ideas| of the materials to do this with and instructions?| Or any other ideas to do this with. Making fishing lures.    Flexane by Devcon is a pretty stiff rubbery two part mix.  Works greatfor making molds.

David Billington · Answer

Dow Corning Silastic 3120 being one that I use for some pewter casting. What your friend has sounds like it might be a heat vulcanising rubber from the description of the process of making the mould, I believe these are better than RTV for taking the higher temperatures of something like lead.tomcas wrote:

pagerton · Answer

I really appreciat all the help and any more ideas are welcome. I amresearching the products that have been listed so far. Would Flexane byDevcon hold up to the heat of pouring lead?

David Billington · Answer

With a max temp rating of about 80C I doubt it would stand up very well. The Dow corning 3120 has a high percentage of iron oxide for thermal conductivity and although it is rated at 250C max it does stand up well to higher temperatures such as pewter which is about 300C or so. It will cause it to breakdown more rapidly but for small volumes it is fine. I have found that baking it to drive out some of the volatiles helps reduce pin holes in the surface as does using a dusting of talc. The baking does cuase some shrinkage around maybe 5% depending on how long it is baked. The 3120 is quite flexible and I had to add a number of alignment pins in order to maintain the registration to keep the split line accurate. The heat vulcanising rubber I have seen used by a jeweller for making moulds for lost wax pieces so you could contact a jeweler or supplier for more info.     wrote:

Hard Rubber Mold? Any Ideas?

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