JA7 is an excellent lead-based, low-cost alloy where relatively high weight is not a problem. It is suitable for larger objects over 50mm wide and over 5mm thick. The casting range is 310-360°C. The sticks average 300gm in weight. Approximate average content: Tin 0-45% Antimony 0-10% Cadmium 0-1% plus Lead.
It is now possible to cast quite intricate metal shapes, such as toy soldiers or model car parts using some of the newer silicones as a mould and low temperature white metal casting alloys. Previously this type of work was done using metal moulds, quite difficult to have made and quite expensive. Amongst the most popular of these silicones are M4670 and M4470. The M4670 is an addition cured silicone and has a firm Shore A rating of 55A, suitable for models with slight undercuts. The M4470 is a condensation cured silicone that has a 60A Shore hardness, making it a harder rubber with a tendency to be brittle, but having good resistance to heat and suitable for castings with few or no undercuts.
Please Note: While melting alloy metals is a simple process, it should never be attempted without suitable protective safety equipment such as goggles and heat proof gloves. It is not something that children should ever attempt without very adequate adult supervision.
