Metal Casting Zone

Hi! Today i made my first casting. I don't know much about casting, but i really want to learn. I had 8 molds and i got 2 of them survived. I used simple gypsum, found in the local construction shop. I made a big fire, i used bellows and charcoal. The molds cracked when i tried to melt out the wax. I think that the cause of problem was that i used only gypsum and i didn't had any metal cylinder around the mold. Am i correct?
There was one more problem. i succeeded casting 2 molds, but the outcome was that the bronze was quite wrinkled - could it be that the molds were not hot enough?
Can you also give me some tips and hints.

With best regards,
Timmo Liiva
Estonia

I've been playing with some plaster with limited sucess. I mix mine with Silica flour at about 50/50. Some go to 33% plaster and 67% silica flour. I had bubles in mine which says I didn't have a complete burnout, wrinkle surface does sound like too cold. It's good to have the mold at about the same temp as your metal.

Hi Timpohvel,

You may have heated the plaster too quickly. If it was not quite dry the residual water will have turned to steam blowing the plaster apart. Warm your molds slowly till absolutely dry throuout.

The wrinkly castings may have been caused by haveing the melt not hot enough.

Keep trying, and good luck

Peter.

I am really happy for your replies! Thank you very much. Now i have some more questions.

What is really silicate flour? I didn't find any matches in Estonian, i tried to asked from the local construction shop also, but still nothing.

Can i replace it with something i have more handy - some kind of a sand maybe, maybe very fine sand - no?

Could it in formula actually be: ZrO2 ?

What granule size is ok? The finest the best?


The problem is that i live in a small town and sometimes there is a little problem getting the resources - but i can order it also, so it's not the major problem.
I'm quite young also, 20. I have not much experiences, but in time i'll become a good bronze caster

Silica Flour is Silica sand ground to a powder. About the same as the plaster. Mix them together dry and then add the water. I melt out the wax in the kitchen oven and then move it to the furnace to try to get all the wax to burn out. If there is some black left around the sprue hole or in the mold then the wax isn't all burnt out yet. It's not fun when the mold starts spitting molten brass back at you and your finished piece probably won't be any good either. I hope to try some in the next week or so.