Making the wax frame.
I call this step the wax frame. I'm sure other people do this, but I figured it out myself. This step allows you to quickly build up the thickness and provide a structural support for both the wax and the metal and at the same time keeping the weight down. This is not necessary for smaller waxes.
Making the frame.
This is a shot of a sheet of wax. It is about 2mm thick. I make it by pouring melted wax on a slab of marble. A wet plaster bat will do the same thing. I immediately cut strips about 2 cm wide, right after the wax has cooled enough to work, but while it is still soft.
Here you see the mold with wax inside and 2 wax strips.
Here you can see some strips applied to the wax form. I apply them to the still warm wax so they will stick. If the wax cools too much reheat with a hot air gun or hair dryer. Run the strips along any edges and up through the form about 4" apart. Press them in firmly. Remember, the bronze will replace the wax so anything you do to the wax will be in bronze eventually. These strips will act as a framework and help strengthen the bronze. The parts in between can then be thinner and act like a skin, reducing weight in the final product.
The next step is to paint more wax on the inside. Pay attention to the edges. Fill the gap between the mold and the wax. Build the edges up more than the body of the piece. If you have a multi piece mold, this will make joining the parts much easier and stronger.
Now go in and paint wax on all the other strips, taking care to fill in all the gaps. Put another coat between the strips. Apply more wax on the high spots to make them thicker. Use a needle to check thickness. If it's too thin you add more wax. You can also add more wax after the piece is de-molded. They are much easier to see then as light will shine through the thin spots.
Let the piece cool and on to de-molding.
