Update! Pictures are up, please go to the end.
I have made my large mortar pattern and want to cast it. This calls for a larger crucible!
I bought some plaster of paris today. I plan to use that for the outside mold. The inside will be made of wood, sanded and polyurethaned. The bottom board will have a aluminum plate over it to prevent sticking. All surfaces in contact with the refractory will be vaselined.
I will clamp the whole mess to the bottom board, and pour in the refractory. When the crucible is dry, I will put a plug under the crucible and re-clamp to push the crucible out.
The refractory I will use is rescobond AA 22 S. It is supposes to be a fairly sticky refractory used for gun- spraying, but hte vaseline should stop that.
Will this work?
Will the refractory cure in a mold like this?
Should grog be added?
I was thinking of adding graphite to increase conductivity. Will the graphite burn out?
Will pounding the mold up and down get all the air pockets out?
This will be a large crucible. I am planning 10" high by 8" wide at the lip. As such, I am planning for 3/4" thick walls and 1" bottom. How does this sound? Lastly, I plan to follow the refractory instructions to the letter for mixing. I have heard people say of mixing drier, but I don't think I will.
Any tips for casting the plaster?
Finally, how would I line up the core piece?