I have always used a Kiln on low heat to de-wax my investment casts with a pan under to collect the wax, then immediately proceed right to burnout and casting temps. I have thought about using the steam method for de-waxing, but on looking do not really see any comparison conversations. I am curious, if the steam de-wax process is used, if the investment mold can be allowed to cool off after de-waxing and cast it on another day after a proper burn it out? It seems like there would not be mold cracking worry there is with the heating furnace method and letting it cool off?
I burn out my investments in a gas fired kiln. (They range in size from 50 pounds up to 800.) I don't gradually raise the heat. I place the investment in the kiln and turn on the burner. When the temperature in the kiln reaches 1000 F. I adjust the burner to keep it there. I burn out the smaller investments for maybe 48 hours. The larger ones for five or six days. I then lift the kiln off of its base and pour the bronze immediately. Here is the kiln; a 55 gallon drum wrapped in ceramic wool and sheet metal. Here is the base The red arrow points to where the burner is placed. The black arrow is the drip pan. I do melt bricks, but, so what? Bricks are cheap. Here is a freshly poured casting busted out and the result I have found the crucial thing about burning out investments is to burn it out for longer than I think it needs. And then even more. And no more than 1000 to 1200 F. This is probably more than you want to know but maybe it will be of use to someone. Richard
I got a definitive answer! If you steam dewax, you CAN let the investment cool off and sit without going directly into the burnout stage without fear of the investment cracking, either shell or block. Apparently the water in the steam does not have the same thermal shock results that heat only introduces. Nice! A good method to use if your investment is not thermally stable and you need to have some time between dewax and burnout. Looks like I will be dewaxing today!
This is actually a continuation of the "Casting Failures Galore!" thread I started. A belt buckle I did for a friend that retired. http://forums.thehomefoundry.org/index.php?threads/casting-failures-galore.2988/ I will put a couple pics on here but they are not current as I had a couple problems and redid most of it. I will also put it in that thread with an update on what happened.
The steaming of the mold worked well, but the steam vapor mixed with the wax. Now there is another step of gently melting the wax/water mix then letting it harden to separate the re-usable wax from the water. I will probably only use the steam (I used our big canning pressure cooker with a container to catch the wax) method if I can not immediately get to burn out, but it is another tool to use if needed.
