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Old 04-30-2021, 07:24 AM
Ed Caffrey's Avatar
Ed Caffrey Ed Caffrey is offline
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Location: Great Falls, Montana, USA
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Compared to a venturi, a ribbon burner is far more efficient... which is often the comparison folks tend to make. Don't take me wrong! A ribbon burner is hard to beat for the amount of heat it can produce, but as with everything we use/do in Bladesmithing....there's a "give-n-take". In order for a ribbon burner to produce the amount of heat it requires a huge VOLUME of fuel. I capitalize that word, because I suspect someone will jump in and say how they run a ribbon burner at a low PSI.... which is a very different thing.

I've built forges that are completely castable refractory, and those that are "hybrids", using both ceramic fiber blanket, and castable. The forge in the images is that.... 1 layer of 1" thick X #8 density ceramic fiber blanket next to the exterior wall, and 2 1/2" thick Kastolite 3000F refractory.
Keep in mind that if you choose to build a full castable forge, the refractory needs to be AT LEAST 3" thick. That's the general requirement to achieve the products full insulation value. Let's say you use a "pipe" that is 10" in diameter, and line it with 3" of castable..... that only leaves you an interior space of 4". When I built the forge in the pics.... I cut the pipe lengthwise, and added in enough so that when the castable was installed, I have 16" of interior space to work with. It just all depends on what each individual needs/wants. For me, I want to produce as large a billet of Damascus as possible. Right now I'm only limited by what my old, broken down body will let me lift/carry/forge/handle. It's not uncommon for me to forge Damascus billets for "cans" that weight 30-40 lbs.

Remember is talked about "give-n-take"? In the case of castable forges, the take a LONG time to heat up. The completed forge in those pics take at least 1 full hour to reach 2350F. But because of the thermal mass, once there, I can dial back the fuel PSI and it will hold/run at that heat all day long. The other thing you need to be aware of with castable forges is cool down.... you don't want to just shut everything off and walk away! You might get lucky for a while and have not issues.... but because these type of forges hold heat so well, they can destroy blowers is the heat gets to them (that's why the blower should always be hanging down as in the pics), of cause anything nearby to combust. I shut the gas off, and leave the blower running until my pyrometer reads less then 900F...... then it's usually safe to shut the blower off.

One last thing.... as a full time Bladesmith, I've always found it best to have two (or more) different forges in the shop. A small, kawool forge with a venturi burner, that can be used for quick or small jobs (non-welding), and then the castable/welding forge. Used when I plan a full day of making Damascus.

Best of luck with it! Don't hesitate to jump on my forum with any questions!


"Nobody cares what you know.....until they know you care."
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