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Coming to the dark side, gas forge build

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Hello all, after being a dedicated coal forge nerd for years now it is time to build myself a gas forge.


The main reason is that my coal forge is small and has only a 2-to-3-inch hot spot, I am making mainly big knives, and having to take a lot of heats down the length of a blade is getting really annoying. I’d like to go for 5 to 6 inches of hot spot to make forging faster and straightening a lot easier.


Fuel efficiency is my main concern here as I have only limited money to spend on this hobby and gas is expensive where I live.


I only intend to use this forge for the actual forging of blades, I have a separate heat treat forge, and I like doing Damascus in coal.

Since I know next to nothing about gas forges, I want to bounce some ideas against some of the knowledgeable folks here.


I have decided I want to go with a blown burner, I already have a very nice blower.


I want to use a boiler vat as the forge body, with 2 inches of wool it will give me 11’’ in length and 7.5’’ diameter.


I have a few questions:


1.       Can I run a burner on lpg instead of propane? I have an lpg tank already and it is cheaper than propane. (This is the type of gas that you can run a car on)

2.       Is there any benefit to go with a ribbon burner in my application? I hear a lot of good things about them but a standard blown burner like in Geoff Keyes sticky thread would be cheaper and maybe just as good?

3.       Would there be any benefit to go to a vertical forge instead of a horizontal one? I mostly see the vertical forges for Damascus, but some people seem to forge everything in one.

4.       My blower has a 2-inch output, but using a 2 inch pipe seems a bit overkill, a gate valve and elbows for 2 inch pipe are real expensive also, can I step it down to 1'' or 1.5’’?



The picture is the materials I already have, I also have a blanket of insulating wool somewhere. 


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I think you can step it down to 1.5" with no issues, and maybe even 1".  If you flatten the burner end into an oval or rectangular section, it will act a bit like a ribbon burner. Using a blown burner means you'll have no issue with using any fuel gas.  Well, don't use acetylene ;), but propane, butane, heptane, or other LPG flavors will all be fine. Before anyone comments, LPG can be any liquified petroleum gas, not necessarily actual propane, especially in Europe where butane is more common. 


Vertical forges tend to be cleaner, scale-wise, and have a more even heat, than horizontal, but if you don't want to spend several minutes holding the steel a horizontal lets you put it down in the forge.  

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I use a vertical forge for everything EXCEPT damascus, I use an 18 x 8 horizontal for that.  Since I do damascus with a press, I can work a long length (18") in a single heat.  Once a billet gets up around 24" it's difficult to reach the controls.  A welded handle or a clipped set of tongs overcomes the issue with pieces falling into the forge.  If I need to I put a piece of sacrificial steel across the forge (mine has two doors on opposite sides of the tank) and rest small pieces on that.


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That should make a really nice forge.  You can definitely step it down from 2".  Mine runs on 1.5" for most of the piping, and then steps down to 1" before it enters the chamber.  With the right blower I can weld without much difficulty.  I'll admit I haven't played with ribbon burners very much, but for general forging I don't personally see much of an advantage to it.  Heat treating is probably a different story though.  

Any idea what the CFM output of your blower is?  It looks pretty big.  You may have to get a little creative with different ways of choking it down in order to run as fuel efficiently as possible.  I try to be pretty fuel conscious as well and typically only have my forge running as hot as i need it to for what I'm doing.  I've used gate valves, choking the intake, and fan speed controllers.  They all work to a degree, I just haven't found a method that I'm truly happy with yet.

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Generally speaking squirrel cage fans do not work well with Ribbon Burners.  You need a blower that develops pressure.  Because of the small holes in a Ribbon Burner there is resistance developed.  With a Ribbon Burner you can control the atmosphere inside the forge.  I adjust mine for a reducing flame when welding and a neutral flame and lower temp for general forging.  The neutral flame also produces less carbon monoxide and it more economical to operate.  I weld in my forge with about 1# of Propane pressure, 2315 degrees F with no flux..  I do not worry about light rust or mill scale.  I do grind off fire scale when restacking.

Check out the Build a Gas Forge and the Ribbon Burner attachments on the Forge Supplies page at


Let me know if I can help you.

About $100.00 plus the hose, regulator and burner using a 20# Propane tank.

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I have a little bit of progress to show, I decided to go for a vertical forge with a blown burner, I have a simple schematic drawing to help me put together a list of parts.


At a industrial surplus place I lucked out and found most of the pipe parts I needed, I am using 1 1/4'' pipe with 1'' for the burner nozzle, nothing beats buying all these parts for a few euro per kilo.B) 


I ordered a gate valve and propane parts from aliexpress, so it will take a while before I can continue the build.


I have a question about the refractory used to line the inside.

Since mizzou/kastolite and such are brands that I can not get on my side of the world, what do I need to look for to find an equivalent?


Is it the same stuff used for pizza ovens, or is it more industrial?






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  • 1 month later...

Just to wrap this up, the forge is done and it seems to work really well, I used it to forge a damascus chefs knife today and it is really efficient to heat a large knife like this evenly.


I ended up using simple refractory mortar, I found an unopend bag lying around, but it is only rated to 1500 degrees so I'll probably end up replacing that.

I need to build a proper stand next, and some other small tweaks but in principle it seems to work exactly as I wanted.





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22 hours ago, Francis Gastellu said:

*tilts head 90 degrees*


Yep, looks really good! :D 

 Haha for some reason these pictures were flipped by my phone, and they didn't want to straighten up. Modern technology is not really my thing.

23 hours ago, Alex Middleton said:

Agreed.  As is the swage block that its sitting on.


On 6/5/2021 at 7:41 PM, Alan Longmire said:

That's a good-looking forge. 

Thanks, The swage block was plasma cut from plate, and is the perfect horizontal surface for stuff like this to accumulate onto. :)

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