How to make a mold for lost wax casting

This is the cheapest and easiest method of preparing a mold for lost wax casting. All you need is your wax sculptures with sprues, plaster of paris, water and containers.

Step 1: Make a plaster mixture

Use two parts plaster powder to one part water. Most plaster packaging instructions say to mix water into plaster. On the contrary introducing plaster powder to water will minimize the amount of bubbles. So start with water and gradually add plaster. Note- plaster powder shrinks as it soaks, you'll use a lot more then you think so be supplied with a big bag before you start.

Comments

[aholbrook]

Wow. Thank you for this write up. I've been looking into doing this for some time (been using lost foam casting) and now this weekend I will try my hand in lost wax casting. Thank you again.

[chakra]

one ever gnawing doubt.. it is said that plaster of paris is a bad mould material if u r casting anything with a higher melting point than of lead.. and disaster for silver or copper.. suggestions?

[Miss Cabbit]

Good question! I have casted silver and aluminum in plaster molds with great results. There is a particular method of doing this though: You have to heat treat your molds. For investment molds a conventional oven works well. Over several hours gradually increase temperature to 400 then gradually decrease to cool as to not crack your mold with temp shock. With lost wax without a vacuum chamber you'll have to get it much hotter to burn out the wax. I use a kiln and ever so gradually increase the temperature to 1000 degrees. Then gradually bring down to cool and leave in the kiln over night. It always works despite varying opinions. Good Luck!

[chakra]

hey!! thanks for the tips!
will let u know next time i cast!