Mizzou vs Kast-o-lite as a forge liner?

[Tenebr0s]

I intend to build a small vertical forge with a 5-6" chamber. The basic plan is to have about a 1" cast liner inside an 8" stove pipe, which I will then wrap in a 2" layer of insulwool and then have that inside the metal forge body. I know that kast-o-lite has superior insulating properties to mizzou, but I'm wondering if that's a plus in this case –– I want the forge liner for both durability and providing an even temperature.

I know the mizzou should make the forge take longer to get to temperature, but would it be better for even temps?

Edit: I had liked the idea of the inner stove pipe both for adding thermal mass and keeping the wool sandwiched between metal layers, so the fibers would never become exposed. But I don't know if it would make the forge take too long to come to temperature...

 

[Stacy E. Apelt - Bladesmith]

The stove pipe sleeve on the outside of the cast liner is fine. You won't notice any difference either way. The wool will be inside the shell, and is not exposed, so that isn't an issue. Kast-o-lite is good stuff, but Mizzou will work if the forge is for general forging. If you plan on welding, get Kast-o-lite 30.
It takes a while to heat up a cast liner but once soaked, it holds temperature well. I let it heat for about 15 minutes to get heated fully.

 

[Tenebr0s]

Thanks, Stacy. I have seen that for smaller forges, some people say 1" of Insuwool wrapped around the stove pipe/cast-o-lite is sufficient. I am tempted, because this is already getting pretty pricy, but I don't want to skimp if it's going to make a worse forge.

 

[Stacy E. Apelt - Bladesmith]

Use 2" of wool. It makes the forge much better.

 

[Tenebr0s]

Ok, then 2" it is!
My basic plan is to have a 5" chamber (I'll use a 5" cardboard shipping tube painted with latex paint in the middle). Then, have an 8" stovepipe around that and pour the 1.5" kast-o-lite 30 liner between the pipe and cardboard. Then 2" of insulwood around the stovepipe. I need to find an appropriate outer metal shell... I have two big squares of insulboard I would like to use for the floor and lid (The floor will get a thick layer of kast-o-lite on top), and the forge-body will just sit on it.
From what I've seen, 14" height is good, with the burner port and doors 3" from bottom and top respectively? I'll use a forced air burner from hightemptools.
For the door openings, I was thinking 2"x3" rectangular steel tubing. I unfortunately don't have a welder here, so I'll be be using angle iron brackets and bolts to secure it to the main body.

This is my first propane forge build, so if I'm missing something, please let me know!

 

[Stacy E. Apelt - Bladesmith]

The cardboard tube and metal sleeve is a good method to cast the liner. A trick to keep it from oozing out the bottom is to put an inch of Castolite in the bottom of a drywall bucket and stick the cardboard tube and pipe in so they are properly centered. Use some wooden spacers between the tubes to keep it centered if needed. Let it dry, then pour the liner between the two tubes. This holds everything spaced right and gives some balance to the setup. It can get really messy if they shift. When the liner has cured for a few days, remove the whole thing from the bucket and knock off the outside and inside extra castolite. and pull out the tube. Most cardboard tubes are spiral wound and you can just start to unroll it from the inside to remove it.

If you have extra castolite or Mizzou, pour about 2-3" in a drywall bucket ( oil the bottom and sides ) to make a great base to sit the forge on. Once fuully dry, carefully turn the bucket over and remove the round refractory base. Set a piece of insboard on it and set the forge body on that.

Don't pour a floor in it. Use your insboard for the top and bottom. Set the forge assembly on the base as above and put in a couple of inches of kitty litter ( the clay type) in the bottom. That way you can take the forge apart in three parts and dump the kitty litter out when it gets full of flux and scale, and put in fresh litter. Also, a reasonably heavy plate of metal sitting on the top will help it stay snug under its own weight. 1/4" plate works fine. Being able to take a vertical forge apart for maintenance is a must. If you are worried about any heat leaking out the top and bottom joints, use stove cement to set them together.

Remember to cure and slowly fire the liner for a good while before using the forge at full heat. It may take a week to fully fire it with short heats and overnight rests to dry, but when done the cast liner will last many, many years at full heat. In use, once fully heated, the forge will stay hot for hours after turning off the gas.