Hello All,

I'm playing with silver casting, and I CAN NOT get my silver to flow all the way through the mold. I don’t have access to a kiln, and won’t for a while…so I’ve been using torches for the silver, and a Multigas camp stove to heat the mold.

For the campstove campstove, I’m using Rothernberger Multigas (70% propane, 30% butane) which can get to (measured) 700°C.

For the mold:
Mouldmaster 5 Kg Stonecast. The sprue is an approximately ½ tall wax cone, melted out in advance. I do put air vents between the wax cavity and the exterior of the mold using pins and nails when I make the mold (which are then pulled out after hardening). I know these vents remain patent, since heavy smoke billows out of them during the pour.

I’m melting the silver in an open-air crucible using a Rothenberger Superfire 2-Turbo Brazing Torch and MAPP gas (methyl Acetylene/Propane Gas Mix)

The process…
I put the mold, upside down, on the Multigas campstove (so that the pour hole is facing the flame directly) and then start melting the silver in the crucible. When the silver is really rolling (7-10 mins), I flip the mold over and bring the crucible’s pour to the mouth of the mold, and let the flame cover both the crucible and the mold for 15 seconds or so…and then briskly pour.

BUT, the silver never makes it through the entire mold. The best I’ve gotten so far is about 2/3rds of a ring.

I’ve tried putting the ring sideways instead of vertical, so the silver has to flow a shorter distance (no good).

I’ve tried two different kinds of oils in the mold first, including cooking oil and a high-temp (400 °C) graphite infused machine oil (the cooking oil worked best actually )…but still no good.

I have successfully done delft clay casting with silver, but this ring is too asymmetrical to do a standard delft clay casting (where the original is pulled out of the clay before casting). I have heard of using delft clay and wax…but the wax would have to stay in during the cast. Since delft clay and plaster have similar thermal conductivities, I’m not sure why one would work and not the other.

I have also thought of mixing a metal powder (zinc, copper, or aluminum...anything with a higher melting temp than silver) with the plaster (SiO2 NOT CaSO4…I don’t want to make thermite ) so that the cast can retain heat better, but I havent tried it yet. I did make a mold out of Stonecast plaster (SiO2) and Aluminum powder…and it was so hard I couldn’t crack it (so I never tried casting in it).

Thanks for any advice! Again, my current limitation is I don’t have access to a kiln.