left: an 18 quart roaster is being used to melt the wax. Never allow your wax to reach a boil, it is very dangerous. Moreover, you will destroy the wax properties. I never set my knob pass 225° . Once the wax is melted I will set the knob just below 200° .
right: The wax is now melted and I am tempting the wax. The first wax cast may be a test cast. That is, I will test to see what the optimal temperature needs to be for this wax when poured into this mold.
The ideal wax temperatures will vary from manufactures; moreover, the size of your mold will also depend on the process used.
The following guide was used for the first wax cast
1. Wax temp at 180° (fill the rubber mold in one non-stop pour and then empty the wax back into your holding container ASAP)
2. Once the temp of the wax in the holding container drops to 170° (repeat the same process as in step 1)
3. The third pour and final was at 150° (this time the wax was allowed to stay in the mold longer... estimated time was about 10 minutes and then poured back into the holding container)
additional notes: This process will vary as mentioned above. Once the optimal temperatures for the wax is achieved, it should be recorded on the mold in order to achieve the same results in the future.
The mold will insulate much heat; therefore, it will prevent you from achieving the correct thickness for your wax cast. The hollow wax cast needs to be about 1/4" thick. Making the shell to thick will make the final bronze too heavy and costly. Making it to thin will cause problems when you remove the wax cast from the mold. In other words, your wax cast may break. For simple molds, you may get away with very thin wax castings. For more complex molds with many undercuts, you will need to make your walls thicker.
If you try to create a sold wax casting you will encounter issues such as high cost, heavy bronze, and deformation of the final bronze (due to the heat generated) This applies to large castings. Very small bronze casting normally do not have these issue to consider.