Introduction: How to Burn Wax Out of a Lost Wax Casting Mold

I did this at TechShop.
Wax can be tough to get out of a mold for lost wax casting especially if you are doing it the cheep way without a vacuum dome. It is possible though.

Step 1: Prebake

The wax burns out at 1200 degrees. Heating a plaster mold to that temperature has to be done ever so gradually because it will shatter from heat shock. This is why we will prebake them raising the temperature slowly in a conventional oven untill it reaches 400 degrees. 

Step 2: Set Up the Kiln

Use whatever you can find to catch the wax so it doesn't spill and burn all over the kiln surfaces. I am using a crucible for one of my molds and a steal bowl for another, supported by refractory bricks and some brick chips around to catch any spillage of wax from my upside down molds. Note: do not use aluminum because it will melt and make a big mess.

Step 3: Transfer Molds Into the Kiln

Balance your molds so they will stay where they are during the burn time.

Step 4: Start the Kiln

Refer to either picture or my instructable on how to set up and run a kiln to do this step.

Step 5: Increase Temperature Slowly

Make sure to take your time in increasing the temperature gradually until it reaches desired temperature. on low for at least an hour them to medium for at least 2 hours then high until temperature is reached.

Step 6: Temperature Check

Hopefully you had the right cone number to get you to about 1200 degrees. I didn't so I am checking it with a laser thermometer. Open one of the peepholes, shoot and pull trigger. The gun will read your kiln temperature. I left it in for too long so the gun is reading almost 1500 degrees. Now I know my molds will be cracked but I don't know to what degree. I am turning the kiln off and letting it cool off slowly to try to prevent even further cracking by shocking it with cold air. Hopefully not all is lost.

Step 7: Get Molds Out of the Kiln

After giving the kiln time to cool down carefully remove molds from the kiln. Make sure to use gloves as they may still be hot even after a couple of hours of cooling. Place them in refractory bricks and not on tarred ground for the pour.
The fun is about to begin. Refer to instructables on how to set up and run a casting furnace, how to pour and safety for the full process.