Question for Peter K.

On the forge you built, I'm curious how you fastened the kaowool to the inside of the forge shell? I was going to set it in place with high temp
mortar but got wondering if I should use some sort of fasteners.
Thanks
Andy
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On Fri, 05 Sep 2003 04:03:29 GMT, "Andrew V"

I just cut it to fit, figuring (maybe not correctly) that it would be self supporting due to the cylindrical shape. It sagged about 1/4" or so away from the shell after heatup. I have seen small stainless or steel skewers several inches long welded to the shell used on larger jobs with flat surfaces, but I couldn't figure out how you would get the kaowool over the skewers in a 14" diameter shell. I didn't think a mortar would work that well, but it might be better than nothing.
Ron Reil would be the guy to ask. He's built bunches of these.
Regards,
Pete Keillor
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wrote:

> I just cut it to fit, figuring (maybe not correctly) that it would be

Pete,
Thanks for getting back to me . I think I'll go with a thin layer of mortar on the shell and put the durablanket on that. if it sags to much I'll add some ceramic washers after the fact. I looked over the pics of your forge in the dropbox very nice job.
Andy
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Andrew V wrote:

I missed the start of this, but I've built a 14" diameter cylindrical forge with 2" insulation with no hangers. It works just fine. I do use the most dense wool (8 pounds per cubic foot). You can buy hangers made out of high temp alloy from places that make glass furnaces, but they are pretty expensive.
Steve Smith

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Steve Smith wrote:

Forgive my ignorance, but could you superheat a tungsten tig electrode enough to bend & use that?
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John L. Weatherly wrote:

Don't know if you can bend them but if you have a TIG, you could join a short piece at right angles to a longer piece. Use DC E- so most of the heat goes into the work.
Also, try using a piece of Inconel 625 or HX TIG rod. You *can* bend this and one 36" long, 1/16" rod would make a lot of hangers.
Ted
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I don't know anything about tungsten. Sounds worth experimenting with if you are making a forge with a flat ceiling. If your forge is cylindrical, you may not need hangers.
Steve
John L. Weatherly wrote:

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i'm about at that point in building my forge too, (loooooong project!) so am particularly interested. I wondered if wood screws ( say 25-30mm (1"+) ) from the outside of the shell would provide something for the outer layer of wool at least to hook onto?
russ from Oz snipped-for-privacy@NOTemail.nu
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Hey all, I would forget the mortar idea for securing the blanket to the shell as it just won't hold, at least not for long. The blanket expands and contracts and sooner than later it will separate form the shell. The hangers might work but Tungsten is expensive and how would you attach it to the steel shell? Here is a trick I learned from glass blowers who have been playing with modern refractories long before us smiths. It is a little more work but in the long run you will have a forge lining that should hold up for many years. The method is as follows: Instead of using one or two flat layers of blanket rolled up into the shell, cut the blanket into narrow strips approx.4" wide x the length of the shell. These strips are then soaked in water (yes water) then folded in half along the length. Now compress the strips between boards to make a nice tight fold, most of the water exits now. Take these folded sections and fit them into your shell. It is a little awkward and the last couple of strips require some fudging around but it really is not that much work. As the strips continue to dry out they expand and self lock themselves in place. Not only that but depending on how wide you cut your strips you can get a nice thick layer of insulation. If you want to get real serious about ultimate durability find a source for collodial silica. This is a water based suspension of extremely fine silica particles. This is mixed with the water you use to soak the blanket in. This substance acts as a stiffener similar to the binders used for making refractory fiber board. The collodial silica also makes a great base coat if you intend to add a hard shell layer of refractory to the exposed lining of your forge. This is a good idea for several reasons not least of which is health related! A great top coat for the inside of your forge is finely milled Zirconium mixed with collodial silica. Glassblowers call this mixture "Z-wash" This coating stabilizes the lining acts as a heat reflective coating and is fairly resistant to borax flux, (which will eat through naked blanket like gasoline on styrofoam)! There are lots more tricks we can learn from glassblowers. A great source of supplies and information is available from Dudley Gibberson
milled Zirconium, burner heads, blanket etc. He also has a great book on furnace design. It is geared towards glassblowers but there is a LOT of data directly related to gas forges. It costs like $35. but it's worth it.
Get it HOT, FAST!
Glen G.
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Hey all, I would forget the mortar idea for securing the blanket to the shell as it just won't hold, at least not for long. The blanket expands and contracts and sooner than later it will separate form the shell. The hangers might work but Tungsten is expensive and how would you attach it to the steel shell? Here is a trick I learned from glass blowers who have been playing with modern refractories long before us smiths. It is a little more work but in the long run you will have a forge lining that should hold up for many years. The method is as follows: Instead of using one or two flat layers of blanket rolled up into the shell, cut the blanket into narrow strips approx.4" wide x the length of the shell. These strips are then soaked in water (yes water) then folded in half along the length. Now compress the strips between boards to make a nice tight fold, most of the water exits now. Take these folded sections and fit them into your shell. It is a little awkward and the last couple of strips require some fudging around but it really is not that much work. As the strips continue to dry out they expand and self lock themselves in place. Not only that but depending on how wide you cut your strips you can get a nice thick layer of insulation. If you want to get real serious about ultimate durability find a source for collodial silica. This is a water based suspension of extremely fine silica particles. This is mixed with the water you use to soak the blanket in. This substance acts as a stiffener similar to the binders used for making refractory fiber board. The collodial silica also makes a great base coat if you intend to add a hard shell layer of refractory to the exposed lining of your forge. This is a good idea for several reasons not least of which is health related! A great top coat for the inside of your forge is finely milled Zirconium mixed with collodial silica. Glassblowers call this mixture "Z-wash" This coating stabilizes the lining acts as a heat reflective coating and is fairly resistant to borax flux, (which will eat through naked blanket like gasoline on styrofoam)! There are lots more tricks we can learn from glassblowers. A great source of supplies and information is available from Dudley Gibberson
milled Zirconium, burner heads, blanket etc. He also has a great book on furnace design. It is geared towards glassblowers but there is a LOT of data directly related to gas forges. It costs like $35. but it's worth it.
Get it HOT, FAST!
Glen G.
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While there has been a lot of disucssion, which is good, it really works quite well to just put the insulation in the forge and let it be self supporting. I've made quite a few forges, 12-14" diameter shells, using 2" thick, 8 pound per cubic foot Durablanket. Never a problem with the insulation not holding itself up.
Consider the inside radius vs. the outside radius of the insulation. At 2" thick, the inside edge is compressed pretty good (assuming you cut it square). It really doesn't want to compress further, which is what would be required for the insulation to fall.
Steve Smith
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Cut your Kaowool about 10-12% long, and force arch it into place. When it cures it should stay put without having to use any supports of any kind. Kaowool, especially Kaowool board, shrinks about 10% when it cures. The old stuff didn't shrink nearly as much, but the new stuff has a very high shrinkage rate.
Ron
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