Forge building ?: 2 layers of 1" wool or 1 layer of 2"

[Travis Fry]

Title says it all, really. I'm fortunate to live in Houston where, apparently 8# 2300deg (or 2600) inswool can be had for ridiculously low prices and no shipping. I have the option of getting 1" or 2" wool, and 2300 or 2600deg. The cost between them all is negligible, so it's a question of what would be best. I plan to coat whatever it is in satanite and ITC 100. The floor and ends will be Insboard, also coated. This will be a horizontal forge for general forging, not for welding (I'll build another dedicated welding forge later).

Thanks in advance...

 

[EdCaffreyMS]

Travis,

Don't waste your money on 2" kawool. Common thinking is that "thicker is better", but not in this case. I've done the tests in my own shop, with the exact same forge bodies.....2" versus 1".....2" (or 2 layers of 1") will take longer to get to a specific heat/temp, and will require about 1-2 more psi of fuel to maintain the temp versus a single layer of 1" (#8 density).

I know, that doesn't sound right, but that's exactly how it works. It's a product of the way kawool was designed....to absorb a given amount of heat before it starts reflecting.....in the case of a forge, you want more reflection then absorption. THE ONLY argument that I can swallow for 2" of kawool in a forge, is recovery time when a large billet is placed in the forge...personally, the difference is only a matter of seconds, so that really doesn't wash with me either.

1" of either the 2300 or 2600 will work well for a "general purpose" forge. DO NOT use the insulboard to completely block up the rear and/or front......there's a reason that most of use use the firebricks.....it's because it allows for "cracks and gaps", which is what you want when you're dealing with a controlled explosion (which is basically all a propane forge is). Any forge that works well, is one that is allowed to "breathe".