First Lost-Foam Casting

[Hawkeye]

You guys have sorted out the language barrier as far as drywall mud goes. Lots of different ways to call it.

When you coat the pattern with some kind of slurry, you do get a smoother finish. Some wrap the foam with masking tape. The main reason I use it is to eliminate the chance of the sand collapsing as the metal replaces it. With a hardened slurry coating, you can use dry sand instead of green sand. No problems with too damp a mix causing steam when you pour. Since the coating is thin, it will allow some of the gases to escape into the sand.

My casting bucket is equipped with an air agitator (seen as the copper tube on the back side of the rim). When you run a small air flow up through the sand, it turns into a dry quicksand that allows you to push the pattern down into the sand very easily. When you shut off the air, the sand settles around the pattern. Same method for removing the finished casting. Turn on the air, the sand starts moving and you can pull the hardened metal out. No dumping.

The steel rig on top of the sand gives you someplace to pour the metal. Easier to hit than a small bit of foam. More importantly, lost-foam requires a ready supply of molten metal ready to flow down as the foam burns out. By pouring a few inches of metal into the reservoir, the flow into the pattern is not interrupted. Since it is smaller than my crucible (the bottom half of a fire extinguisher), it will be easy to drop it in for the next melt.