Core material for ceramic shell casting

Does anyone know of a good core material that can be used in ceramic shell casting and a supplier? I've used core materials from Ransom and Randolph but they are plaster based and emit gasses that cause voids in castings.

Thank you.

Steve L.

Steve,

Try this:
http://www.unicastdev.com

HAVE YOU THOUGHT OF FIBERMESH CONCRETLE? THATS WHAT I AM TRYING NEXT. LET ME KNOW IF IT WORKS OUT FOR YOU. BEACHPARTYOFONE

[This sounds like good suff, Mark. Have you used it a lot? Will it really form a totally-enclosed core that doesn't outgas? Can you use it in investment castings as well as shell and sand? Any tips for dealing with it? And how much does it cost? Enquiring minds want to know...]

Andrew Werby

foundry work, correct? Are you casting a core and then coating the core with wax which then is treated with the usual ceramic slurry and then cast in metal? Regards, Don

dangerous. Concrete retains way too much moisture and the chance of a hot metal explosion would be very great. Don

Ok found itage 88 'Methods for MOdern Sculptors' by Young and Fennel. They speak about two formulas. One which uses your Ransom and Randolph. Casting Investment 903 50% Satin Cast(Kerr) 25% Refractory cement 23% Chopped Fiberglass 2% Percents by weight Fiberglass is cut to 1/2 to 1 ' lengths (ugh, cutting fiberglass) Ceramic suppliers carry the cement. Dry mix the ingredients. Mix with 80% distilled water until the thickness of unthinned latex paint. Then add liquid colloidal silica until like yogurt. You should have about 15 mins to pour the core. Dont forget those core pins. The book talks also about inserting a wax covered steel rod to use as a holder to apply the slurry. When dewaxed the rod falls out. Don

I have not tried it yet, but I have tech information from the supplier. Generally they liscence the process to foundries, but they sell a variation of their product to art foundries without liscence.

They have been making material for ceramic cores for 50 years so I'm assuming it works pretty well. You have to fire it to remove atomic water of course, but it sets up at room temp (5 min.) and they claim it is very easy to remove as it has great porosity for quick burnout. Sales guy says you can remove it with an air blast but it holds up to the metal erosion.

It costs around $500 for 3600 cubic inches of slurry. They claim it drops to $.085 per cubic inch with quantity.

This is probably wprth it when you consider labor savings of a good core material for those hard to cast 12-24' sculptures.

I'm going to try it. I'll report on it.

Mark Parmenter

Yes, I do my own foundry work. I pour a hollow wax and fill the cavity with a core material and then dip the wax in the ceramic slurry.

Thanks, Steve L.

I haven't tried mixing the formula myself but according to R&R, the mix I ordered from them was made using that recipe. (The book mentioned that they had a core material and they didn't so they decided to make the mix.) I had problems with gas using it. I think there is plaster in some of the ingredients and it emits some kind of gas under extreme heat. I used to think the problem was that the core wasn't completely dry but I kept shells with the cores in the burn-out oven for a long time and am convinced they were dry.

I was in a foundry once that said they had a good formula but they wouldn't give the recipe.

Thanks, Steve L.

I called the company and it sounds like a good product.

Thanks, Steve L.

hai,
would you explain what is this fibermesh concretle