How do I make a ceramic mold for metal casting using Colloidal Silica?

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Question:

I have a wax figure i would like to cast into metal bColloidald to coat it with some sort of ceramic material except clay to fire melt the wax out leaving a perfect mold for a metal pour!. Is this Colloidal silica liquid and I add sand to it or is it the other way around!. Or do I need to use something completely different!. Www@QuestionHome@Com

Best Answer - Chosen by Asker:

When I took a bronze casting class we did the ceramic shell process like you are talking about!.

You can buy the materials from http://www!.ransom-randolph!.com/
They make the materials for ceramic shell and other types of investment!.

The process we did involved dipping the wax in the slurry then put it on the table and coated the still wet pieces with sand!.

This was done for several coatings letting it dry between!. We started using small fine sand to heavy big grains of sand!. This slowly built up the shell and was then burned out
after it was the right thickness and size!.

I suggest you contact Ransom and Randolf for a distributor near you for the materials!. (see the link above) I hear that they ship all around the world but a distributor can also help with technical advise!.

EDIT Casting metal is best learned from an instructor!. Reconsider doing casting on your own if you haven't taken several class, and are willing to undertake all the steps knowing the proper safety measures!. During the pour several of us put on the heavy safety gear!. We had an instructor that had done the process many times and maintained the equipment!.

Please contact a foundry!. Have the size and weight of your project so you can discuss a price quote!. Discuss what their fee structure is and what you would be permitted or required to doWww@QuestionHome@Com

I think I mentioned this before!. What are your options for the burnout!? How are you going to to get rid of the wax!?
This will determine to some extend your options for investment!.
If you can run a burnout kiln for 3 days I would strongly recommend using plaster/sand investment instead of ceramic shell!. If you can use the facilities of an art foundry they will only do ceramic shell and you will need to do ceramic shell!. You need to follow their instructions!.

1) what way are you using to get rid of wax!?
2) how many pieces are you making and how large, are you going to join with a group of other people contributing their pieces!?
3) what is your facility for casting
4) what metal are you using

The answer to these questions will to some extent determine useful type of investment!. Ceramic shell is for example not useful for jewelry sized objects!. It's too hard to remove easily and the removal process will break delicate structures!. also slurry will set rock hard if you don't maintain it and that investment process takes usually a day or two!. Plaster/sand is fast to invest but needs much longer burnout!.

I would very strongly recommend to take a class or at least read a book!. As far as I remember the book "from clay to bronze" has a pretty detailed descriptions of lost wax casting!.Www@QuestionHome@Com