ArtMetal

New here - hope I'm doing this right! I have a question about cores for ceramic shell casting. I teach a foundry class, so I am no newbie. Generally for hollow pieces I cut out a section or make sure the piece is designed so that the center will build up a shell and be able to dry properly. But, I am now doing some foundry work for another artist out of my studio of some small animal figures. These are a little too big to cast solid (though I can if necessary), but a little too small for a large enough opening to allow the shell to make a strong core -- soooooooo.....I have been looking into using some sort of core material.

Several options I have found so far:
1) An investment/refractory mix in Ron Youngs book for the modern sculptor, but the book is 25 years old.

2) a mention of cement fondue (which seems to be a high alumina cement) mixed 2:1 refractory to cement. Stucco can be used for the refractory. This is in "fine art metal casting" by Richard Rome and Hamish Young.

3) If there is an opening that will close up after 4 dips or so, do the 4 dips, then fill the inside with dry stucco and seal with some slurry. Allow to dry and continue to dip - the stucco will support the thin inner shell.

Question, does anyone have any experience with this? With the quick burnout times of the ceramic shell, I imagine this could cause an issue with solid cores. I could put some vents in the solid core - but would the burnout times or temperature be different? Other ideas?

If you would like to see my work take a look at my website: http://www.rotblattsculpture.com