Which Castable Do You Use? | The Forge Fire | Forum

I've used a number of different products. They all have worked. So I just buy what I find. I did have one many years ago that I particularly liked called "Refracrete". Not only was it castable, but it was moldable. Most of the castables need to be in a form or they slump. Currently use "Cast-o-lite" 'cause that's what the ceramics place has.

I have only made them with ceramic fiber with a thin castable lining. If I were going to go all castable I'd use one of the insulating castables like Kast-O-Lite (which will be about half as insulating per thickness as the fiber insulation). Mizzou is dense, hard and strong, but it's a very poor insulator. The "insulating" castables are about halfway between Mizzou and fiber.

I have never used castable refractory but I have made moulds for refractory for the steel mills. Often they had a means of casting a hard internal shell then an insulating refractory poured around that. They use shortening liberally applied as a release. They also use a large vibratory table to make sure all the bubbles are vibrated out.
The shop I used to work at had some large moulds that they poured a two part foam into. The foam pieces then had refractory poured around them down at the steel mill. The foam was then gouged and burned out. I have often thought that making a plug out of insulating foam would be a good simple way of making a forge with a shape that would be difficult or impossible to slide a plug out of. Woodworking power tools work well on foam and allow you to work more accurately than using a razor knife.

Dave Lisch makes a lot of forges and he takes Mizzou and mixes it into a slurry. He then takes Kaowool (1" thick) and soaks it in the slurry. Then he lines his forges with the soaked Kaowool and lets it set up. He has a lot of happy customers out there with forges like this.