Drip casting revisited

[Ron Coleman]

I've been brushing up on my kiln casting techniques recently and finished a nice cast muller this evening.

After a false start with the wrong wax for the model I poured a 50/50 silica and potters plaster mold with fiberglass shorts mixed in for added strength. I found that steaming the wax out is a far better technique than trying to melt the wax in the kiln, at least for me. I think the moist heat from the steam is easier on the mold that dry kiln heat. I ended up using red casting wax from Sculpt.com for the model.

I used an electric skillet, put the mold on some sticks across the rim and tented the whole thing with aluminum foil to keep the heat and steam in. As soon as the mold got up to temperature the wax ran out. The mold was only poured a few hours before the steam-out.

After 2 days air drying I heated the mold slowly up to 325 f to drive off any moisture and cooled it.

Last evening in a 5 hour cycle I did the casting and every thing worked like a dream. The plaster/silica mold held up to the 1 hour soak at 1700 f and then the 18 hour anneal and cool down cycle. The mold only had hairline cracks and had to be chipped away from the glass, no fins or flash on the glass.

The only problem I had was the entrainment of a few bubbles as the glass flowed into the mold. I watched the process and as the glass hit the side of the mold it would fold back on itself and trap a bubble once in a while. Not really sure how to solve this problem.

The glass was BE clear casting cullet.

Ron

[watershed]

Sounds good. I'm using a wallpaper steamer(minus the large pad) for steaming, works great.

Another drying tip (though the molds are still in). Go ahead and load the kiln. Put a window fan, on LOW, over the top,Pointing IN, for as long as you can stand it. Good drying juju.

But my molds are heavy and thick. YRMV

Greg