Introduction: How to Make a Propane Forge

Picture of How to Make a Propane Forge

In this Instructable I show you how to make a high efficiency propane forge. I have made a few forges so I have a good idea how they go together but I will give reference and credit to Ron Reil and his designs, that is where I learned how to build them over 12 years ago.

This forge can be used for knife making, blacksmithing, glass making or anything else you can think of that requires heating up stuff to a really hot temperature.

I have access to a welder so I was able to weld some parts together for this forge but if you don't have access or know how to weld, an option is you can braze the parts together or be creative and bolt things together.

Not included in the steps is how to build an operate a propane burner, I have another Instructable for that, which you can check out here:

Important Warning: Do not attempt this Instructable if you do not have experience with propane and how it burns. If you are not comfortable around propane do not attempt this. When propane if used properly is a very safe fuel but bad things can still happen. This burner is very large and can damage you and property. You have been warned, I take no responsibility if something goes wrong.
Always wear safety equipment when lighting and working on the burner. At a minimum, safety glasses or face shield, cotton long sleeves or leather, do not wear synthetic materials as if they catch on fire they will melt to your body.

Lets get started!

Step 1: Video of the Forge Construction

I highly recommend watching the video for the construction and operation of the forge. The written steps follow.

Step 2: Materials and Tools Used

Picture of Materials and Tools Used

I bought the kaowool and refractory from the rest I found locally at the hardware store.

A note about ITC-100 refractory used to coat the kaowool, it works by far better than any other cement/mortar like refractory I have used in previous forges. I notice that it heats up quicker and uses less fuel than a previous forge using a regular kiln refractory (don't remember the type). If you have the extra money spend it on the ITC-100.


  • Airtank or freon tank or propane tank or steel tube (for the container), at least 10" wide
  • Kaowool (ceramic blanket)
  • Kaowool board
  • Firebricks
  • ITC-100 refractory or some other type of brush-able refractory.
  • High heat stove cement
  • High heat BBQ paint
  • Steel tube or iron pipe fitting sized for the propane burner
  • Piece of 14 gauge or similar thickness sheet steel
  • Piece of 1/8" x 3/4" steel flat stock
  • Piece of 1" steel square tubing
  • 2" x 10-32 bolts
  • 3/4" coarse thread screws

Here is a list of the main tools used, some may not be listed.


  • Mini-grinder with thin kerf cutting disc
  • Files
  • Drill
  • 10-32 tap
  • putty knife
  • good quality respirator
  • disposable gloves
  • vacuum
  • welder or propane torch for brazing
  • 1" paint brush

A propane burner will be needed to power the forge, see two different designs here:

or see this video for another design

Step 3: The Forge Body

Picture of The Forge Body

For the forge body is a portable air tank. But you can use anything that is similar, such as a used Freon or propane tank. I have used a steel pipe I found at the scrap yard that worked very well.

The air tank I am using has a built in stand to keep it from falling over so this saves me a step or else I would need to add some feet. I'll leave it to your imagination to add the feet to what ever tank or tube you use, suggestions are some large bolts or weld on some tubing.

I used a pot that was a good size to trace out the size of the opening. A compass could be used as well. I cut the ends off both ends of the tank using a thin kerf cutting disc on a mini grinder.

Step 4: The Burner Mounting Tube

Picture of The Burner Mounting Tube

To mount the burner a pipe nipple was tapped and welded to the forge bottom.

The placement of the tube was at the top of the forge and placed on an angle. The hole was marked and then cut out, I didn't have a hole saw the proper size so I drilled holes all the way around the circle and then used a Dremel with a cutting disc to cut it out.

Then the pipe nipple was tapped using a 10-32 thread tap. The bolts will hold the propane burner in place for mounting.

The nipple was then welded to the tank, if you don't have access to a welder, another option is the tube can be brazed to the tank. If you can find a flange for fencing the proper size, it could be bolted to the tank.

Here is an Instructable for building a propane burner or Google Ron Reil propane burner:

Step 5: Forge Floor

Picture of Forge Floor

The bottom of the forge needs to be lined with fire brick. The firebrick is a durable floor material and can be replaced if you do any amount of forge welding as the flux will eat away at the brick.

The bricks were cut to fit the bottom of the tank and one brick was cut into 1 inch wide pieces as spacers to raise the floor bricks up from the bottom of the tank. See pic.

To cut the brick a wet saw was used, other methods are using a chisel and hammer but the bricked I used were too brittle to cut using that method.

The bricks were placed and then cemented together using high heat stove cement.

Step 6: The Ceramic Blanket and Board

Picture of The Ceramic Blanket and Board

The key material for the forge and insulation is the ceramic blanket and board, it goes by brand names such as Kaowool. The blanket can be purchased in different thicknesses, I recommend getting 1" thick rather than thicker ones as it is easier to work with. For this forge, 2 layers of 1" will be used.

The board is a rigid ceramic board and will be used for the opening and back wall of the forge, thickness is 1".

Important! When working with these ceramic material wear a good quality respiratory and vacuum up any fibers after cutting. You want to keep these fibers out of your lungs!

Step 7: Installing the Ceramic Wool

Picture of Installing the Ceramic Wool

The circumference of the forge was measured and then the blanket was cut to size. It is better to cut it a bit larger so you can trim it down. To cut the ceramic wool use a sharp utility knife, it is very similar to working with house insulation.

Two layers were installed and the bottom of the fire bricks had some installed between the spacers.

The opening for the propane burner was cut open as well.

Step 8: Back Wall

Picture of Back Wall

The back wall is the exhaust port and also can allow for longer pieces of metal to be worked in the forge. It is made from the ceramic board.

To make a template a piece of plastic was draped over the opening and traced out. Then it was transposed to a piece of foam board or cardboard and then traced onto the ceramic board. A utility knife was used to cut the board.

The blanket in the forge compresses so the ceramic back wall was held in place by friction.

Step 9: Front Opening

Picture of Front Opening

To keep the inside of forge so it is accessible a removable front opening was installed. On the body of the forge a piece of 1"x1" square tubing had bolt holes tapped so 10-32 bolts would could be installed. Then the square stock was welded to the body of the forge, again brazing could be substituted.

A front "U" bracket was fabricated from a piece of 14 gauge sheet metal, template was free handed, some holes were drilled for attaching the board. A piece of flat steel stock was bent and welded to the "U" bracket.

A piece of ceramic board was cut that was larger than the opening of the forge but the size of the opening is up to you as it needs to be big enough in my case to have tongs fit in and out. It was fastened to the "U" bracket using coarse screws.

The "U" bracket assembly is held in place with by the flat steel stock in the square tubing with the tapped bolts.

Step 10: Refractory Lining

Picture of Refractory Lining

The ceramic blanket and board needs to be stabilized so fibers do not become airborne when the forge is in operation. There are a few choices for the refractory lining, I am using ITC-100 HT which looks like a cement/mortar, however it can with stand extremely high heats. It needs to be mixed with water so it becomes like a slurry that can be applied with a paint brush. The consistency should be like thin pancake batter.

It was slowly brushed onto the inside of the forge and outside, just make sure to cover all exposed ceramic fiber surfaces.

Other refractories can be used and the application will be similar.

Let the refractory dry before operating the forge.

Step 11: Misc Pic

Picture of Misc Pic

Paint the forge with high heat paint, especially the places where there is exposed metal.

Here are some pics of the forge with measurements included for reference.

Install the propane burner into the forge opening and hold securely in place with the bolts. You want the burner so the nozzle is flush with the inside of the forge wall.

Step 12: Operation of the Forge

Picture of Operation of the Forge

Put some safety glasses on and have a fire extinguisher near by. To light the forge, use a long BBQ lighter and put the flame near the burner nozzle inside the forge. Turn on the propane slowly and the forge should ignite. Leave the forge at low power.

Once the refractory is dry, it needs to be cured. Don't operate the forge at full power until the refractory is cured. Run the forge at a lower temperature for 15-20 minutes to let the ceramic fibers and refractory lining "set up".

The forge is ready to be used. Crank up the temperature of the propane burner and observe to make sure everything is working properly.


bob_the_builder21804 (author)2017-12-24

I LOVE this instructable. I've been wanting to make a forge for various metals for quite a while, and I'll definitely be referring back to this very clear and detailed instructable when I start mine. I work at a steel mill and have collected some scrap materials from when maintenance has been done to our hydrogen furnace, and after watching this, I'm more encouraged to get started, Great job, and I appreciate you posting it. Big, big thumbs up.

Magnusf0711 (author)2017-12-12

Wow. This is so so cool. I am 100% going to make something like this. You did a wonderful job explaining all of the instructions. What temperature can this forge get to?

chadaustin99 (author)2017-04-26

if the ITC-10 is too expensive for me, what can I use as a refractory lining in its place, like is there a specific one you recommend for this application that is a less expensive substitute?

Kraeik (author)2017-01-10

Just a word of advice, Reil has not updated that site in over 10 years. When he put the info out there the acceptable coating for Kaowool to reduce the possibility of airborne ceramic particulate was just the ITC 100, it has since been challenged and updated. It is now advised that you first use, at least, a rigidizer on the Kaowool before coating with the ITC 100.

The ITC 100 alone is no longer suggested or recommended for eliminating airborne ceramic particulate from the wool. That stuff is pretty bad for you.

MaxPower1977 (author)Kraeik2017-01-11

Yeah I have wondered that myself, I have done some research on this and have not been able to find any consensus. Do you have any idea what to use to stabilize the kaowood.

rakrupski (author)2016-12-29

I built a propane forge, but instead of cutting an old propane cylinder, I used a stainless steel cooking pot:

Using soft firebricks to make a rectangular chamber, then wrapping it in 2 layers of Kaowool makes a cube that fits perfectly in the 13 inch diameter pot. The rear of the cube is also insulated from the rear (bottom) of the pot with 4 inches of Kaowool cut into 13 inch diameter circles.

Then, the propane plumbing is attached to the rear of the pot for mechanical stability and there you have it... a forge with almost no cutting required (aside from the hole for the burner and the small holes for the screws in the rear).

I did later cut a rectangular hole in the lid of the pot to cover the front - but this is not really necessary.

Questor1 (author)2016-09-13

I want to melt 260 Brass scrap from cut-up materials in a small ?rectangle? ceramic cruicible to make small 260 Brass ingots. These small ingots would later be re-melted by me for casting small and thin brass
parts from "Lost Wax" casting molds.

1.) Can a ceramic front door or gate be safely and effectively added to help increase internal temperatures more quickly while reducing heat loss? This could also reduce higher Propane usage and costs...

2.) How much or what volume of Propane Gas is used to heat up your Propane Forge during an average use? I realize this depends on the Forge construction/materials, the temp/humidity/weather conditions, and the amount/type of metal to be melted. However, I'm trying to roughly estimate the total propane usage and cost for average use.

3.) Which Metal Element names were you able to effectively melt in a Ceramic Cruicible?

4.) Did you place the metals to be melted inside the Propane Forge when it is "cold" or else after the Propane is "hot" and at high temperature?

It seems that placing these metals while the Forge is "cold" saves heating time, reduces propane costs, and may be somewhat safer than trying to insert a ceramic crucible into a hot Propane Forge with a small opening...

5.) Is your Propane Forge recommended to be used only on concrete bricks, or a concrete floor, or in a sandy "pit" ?

Thanks, Steve

Cincinnati, Ohio

astrong0 (author)Questor12016-12-27

So, I have a propane burner I use in my forging. I can get about four hours of continuous use until the temperature of the propane gets too low, the flow stops. So I only have that long to forge. Now it only really would take about 45 minutes with my setup to get hot enough to melt brass. Maybe an hour to get it to casting temp. Hope that helps. I can post a pic if need be.

MaxPower1977 (author)Questor12016-11-08

You could make a door from ceramic wood and a metal brackets. Not sure but I think a full 20lbs tank of propane would last around 5-6 hours of constant use. I use the propane forge on a work stand. But best to use it on non flammable area and outside.

I don't have answers for your other questions.

KryptoTSD (author)2016-12-25

I'm gonna try this. I want to get into blacksmithing and bladesmithing, you know, making knives, daggers, swords, maces, war hammers and the lot...

astrong0 (author)KryptoTSD2016-12-27

Do it!!! It is a little expensive to start out unless you get an anvil of some sort for free-ish. But it's so amazingly rewarding when you get something done. Do it!!!

GTO3x2 (author)2016-09-13

I thought forging was the hammering and shaping of metal. I don't know how the furnace, or oven, has taken on the name as "forge" so much. BTW people, there is cold and hot forging.

Nice looking oven BTW !

astrong0 (author)GTO3x22016-12-27

True there is cold and hot forging, but you will never get the strength that hot forging produces in steel. Copper would be fine, to a point so would bronze but not steel.

ShaneM6 (author)GTO3x22016-09-13

Actual the hearth has been called a forge for atleast a couple thousand years, the act of making something is called forging. They are not called a furnace or an oven, those are different units used for different processes. I would suggest you do a little historical research on the subject if you have an actual interest in it.

JetMechanic (author)ShaneM62016-12-26

English has developed over the last 1400 years, nevertheless that's plenty long enough to make your point.

MaxPower1977 (author)GTO3x22016-09-13

Thanks! and yup no idea why they use the term forge.

Mark 42 (author)GTO3x22016-09-13



a special fireplace, hearth, or furnace in which metal is heated before shaping.


the workshop of a blacksmith; smithy.
astrong0 made it! (author)2016-12-27

I'm getting there!!! A slightly different design but close enough.

aebe (author)2016-12-25

You can increase the efficiency of your forge by preheating the air . I have done this on forges by blowing combustion air through a heat exchanger attached to the rear of the forge .

KryptoTSD (author)2016-12-25

Oh, yeah, cutlery for in the kitchen and little clench nail spoons, too! You can never have enough knick knacks laying around...

John T MacF Mood (author)2016-12-25

Brilliant work! I wish I could go build one right now, but lack a few tools, and a lot of the funds needed for materials. Most of what's shown that can be obtained as scrap, I'll easily barter for at my pal the recycling metal dealer down the street.

Anyone with extra fire wool or firebrick can email me at aa4pc (at), I'll gladly barter or buy.

Craig Gibson (author)2016-10-12

overall cost?

Aisofidaho (author)2016-10-01

Could I use and aluminum thick walled tank or does it have to be steel? Took a descent size water tank out of my 1965 camper and it has the inlet tube in the middle of the tank already.

MaxPower1977 (author)Aisofidaho2016-10-02

Nope you can totally use an aluminum walled tank, the outside does not get super hot, at least not hot enough to melt aluminum. The metal is only there to hold the refractories in place.

polymarkos (author)2016-09-29

Is there anything to prevent the kaowool from collapsing? I used one of these designs for a while, and the kaowool degraded until I had to change the lining. I tried using stainless steel wires to keep the roof of the lining in place. That didn't work too well.

On mine I used two of Frosty's T-Burners; much cheaper and easier to build than Ron Reil's designs, though not nearly as efficient.

MaxPower1977 (author)polymarkos2016-10-02

I've never had an issue of the wool collapsing, I try to keep the fit super tight so friction holds it in place since it's kinda like an arche.

GaryN26 (author)2016-09-14

Very nice little forge incredibly easy to follow instructions and photos.

Man Up (author)2016-09-14

I have been studying forge designs for a while now so I can replace my cement-bucket-forge with something better. This is by far the best design I've seen, and incorporates all of the best practices of every other home-brewed forge I've seen out there. This will be the forge I build.

If there was one thing I would add (and literally, it's the only one thing I would add) - all of the burner designs out there are intended for diagonal mounting, but do not include any strain relief protection for the hose. I strongly recommend people buy a 2 1/2" spring from their local hardware store, and slide it over the end of the fuel hose where it meets the burner assembly. The spring will take the strain of the hose and spread it out. Without this, the strain will result in hose failure where it meets the connector, and that could be very bad.

Robbin1 (author)2016-09-13

I've looked at a lot of homemade forges here on instructables and many other sites, but this one is by far the best design I have seen!

Great job!

I need mine to be able to melt gold and platinum as well as knife making, so I was wondering if you took the end you cut off, fill it with the kaowool and hinge it to open and close; if that would help the temperature rise high enough? Also, the addition of a blower could help as well. You would only use the outside door to heat and then retain the heat, while still using the front cover you made with the board and half moon steel. Just cut a notch for the adjustable arm on the cover in the door?!

Any thoughts on how that might work? Of if it would?!?


agaye (author)2016-09-13

what's the highest temperature it can reach? enough to make Damascus?

MaxPower1977 (author)agaye2016-09-13

With the ITC-100 it should easily reach forge welding temp. You may have to crank up the PSI depending how well your burner works.

brianhunt (author)2016-09-12

Ceramic board for the door. What a good idea, now I can stop trying to find time to weld up a door for my propane forge. I will make up something like this instead.

Mark 42 (author)brianhunt2016-09-13

I bet large ceramic tile would make a nice looking door.
Might melt the glaze though.

MaxPower1977 (author)Mark 422016-09-13

That's a really good idea.

russ_hensel (author)2016-09-13

I bought the kaowool and refractory from, the rest I found locally at the hardware store.

Note that a "," has crept into the url, might test all and clean up bad ones?

russ_hensel (author)russ_hensel2016-09-13

Also may be a more useful link.

MaxPower1977 (author)russ_hensel2016-09-13

Thanks, fixed now.

MikeH36 (author)2016-09-13

Safety wise, your water saw leave a bit to be desired since water and electricity don't play well together....

Drake88 (author)MikeH362016-09-13

I have used a small portable water saw in the past and the design was very similar to the one in the picture. As far as could tell from looking at the one I used, it was exactly the same as an average 'skill'-type saw - except that the housing around the shaft was better sealed to prevent water from entering the motor.

The one I used had the water line running over the top of the blade protection and the dripper was on the front side of the blade. The water line was also smaller, but that doesn't matter. It was a fairly old water saw belonging to my grandfather. I couldn't find a manufacturer name or emblem anywhere on it, but it worked perfectly for cutting some 1/2 inch tile we used for a bathroom and shower floor.

As long as the water is kept away from the motor and any electrical items, it is safe.

MaxPower1977 (author)Drake882016-09-13

Also I use mine with a GFI plug.

SuperKariO (author)2016-09-13

You can increase the temperature in the forge by using a mixture of
propane and air. My father designed a forge with a burner mixing the
gases and thus achieving over 2000 degrees celsius temperatures. This
allows to do welding and especially damascus steel. This page ( is
unfortunately only in Finnish but there is a picture of the forge and
the burner (bottom of page)

TCZS (author)SuperKariO2016-09-13

Thanks for link.

BeachsideHank (author)2016-09-12

You advise about clothing is well founded. In the early '70's, the U.S. Navy was changing work uniforms from dungarees and cotton shirts to synthetics, rapidly abandoning this change when it was found personnel in the engineering spaces who contacted hot surfaces had the synthetic material melted into their flesh, kind of like Napalm, so it was back to the old stuff.

Mark 42 (author)BeachsideHank2016-09-13

Wool is somewhat flame retardant.

JonathanC193 (author)2016-09-13

Any idea what the volume is?

deluges (author)2016-09-13

Looks really cool. Pun intended.

tipigeon (author)2016-09-12

Wow this looks really good! Might try to make it :D

(does it have enough space for a crucible to melt aluminium?)

MaxPower1977 (author)tipigeon2016-09-12

Depends on the size of the crucible :) But you could always make a larger one from a metal bucket. There are a few Instructables on making one, I made one based on the design of "The King of Random" but I plan on remaking one with the left over Kaowool I have. His works good, but it takes too long to heat up as the refractory is mostly plaster of Paris whereas ceramic wool and ITC-100 is superior but of course costs more.

tipigeon (author)MaxPower19772016-09-13

Thanks for the info!

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