OK, poked around for an hour, and haven't found the info I am looking for. I am building a smallish gasser ustilizing 2 freon jugs and 2 burners. I am wondering however, just how much lining I am going to need, in terms of thickness. Is 1" wool likely to suffice or should I really go to 2"? I do plan on coating with ITC100 for reflection, and some variety of rigidizer like ITC 200 or the like. I know that thicker is better when it comes to insulation, but I would imagine there would be a point of diminishing returns. Anyone want to chime in? Pretty please? I am almost back up and running after being forced to switch to gas due to a shop move.

2" seems to work best for most

Save the cost of the insulation by using less gas. Also if you do 2 1" layers you can then just replace one of them when the inside gets tore up.

Yeah, I had planned to do 2 layers Thomas if I went with 2"... I just wasn't sure if 2" was needed or if it was just a slight improvement.

Slight improvement? My assumption was that 2" would at least double the insulation value of 1"...

When I went from 1" to 2" is when we started *melting* steel in the forge at the same setting on the regulator. Backed it off and saved gas and still had hot steel to work.

Mac Talis Iron, You will definately want to use two layers of Kaowool or similar insulation. If you would like a guide to the sizes to cut your insulation for the freon bottles you mentioned you can do a quick search on this forum for "freon can furnace dimensions" and you'll find a jpg. attachment of a drawing giving sizes for the pieces needed.

Hope it's helpful, Steve G

Yeah, I had planned to do 2 layers Thomas if I went with 2"... I just wasn't sure if 2" was needed or if it was just a slight improvement.

Mac, in your first sentence above it almost sounds like you're thinking about 2 layers of 2" kaowool (4"!). If that's right, a single layer of 2" blanket is all that you should need (or 2 layers of 1" blanket.)

I was just wondering if there a point of diminishing returns is all. I got it dealt with and she gets plenty hot. Thanks guys, always been a coal man... all my gas experiences were with others' forges.

I'm using 2" 2600deg fiber board with the coating of ITC added. Couldn't be happier! My latest forge is designed exclusively for welding. Forced air with ajustable airgate valves and individual needle valves on each of the two burners. Having control over the important elements is key. Have more than enough air available then chock it back to ideal. Same on the propane, I have a regualtor at the tank then a flex hose to the cutoff ball valve, then the line splits...goes to needle valves and from there the gas pipe is weled in place in the direction of the air flow. The whole thing looks like something Doc Brown would have made in his laboratory. Not pretty but it gets really hot in a hurry. My internal dimensions are 4" wide 5 "tall and 12" deep.