How to Make a Propane Forge

by AndrewW1977

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Intro: 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:

https://www.instructables.com/id/How-to-Build-a-Pro...

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

I bought the kaowool and refractory from http://www.psh.ca 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.

Materials:

  • 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.

Tools:

  • 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:

https://www.instructables.com/id/How-to-Build-a-Pro...

or see this video for another design

STEP 3: 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

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:

https://www.instructables.com/id/How-to-Build-a-Propane-Forge-Burner/

STEP 5: 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

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

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

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

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

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

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

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.

51 Comments

FredFB 1 year ago

I made one similar to this using an old freon can. I bought the spun ceramic blanket from Amazon and the floor I made from a mixture of fine sand and Plaster Of Paris...I made bricks of this as well by adding small bits of steel wool to make them less brittle. Buying the burner made sense because I would have spent as much on the parts as I would the completed unit.

SamuelH111 4 years ago

I have a few Questions. I have a whole aluminum beer cage. Witch is a little longer and the inside diameter then the air tank. If I used the same layers of the blanket. Along with a couple of coats of refectory cement. I welded some aluminum stock for feet and a handle on the top. To make it more portable. Is the a formula for the inside diameter and length. To figure out what min. & Max. size hole I should have in the front and one in the back ..if needed. I texted a long text with questions and it disappeared. So I'm sending just part of the questions.

BakerBoy7 1 year ago


Aluminium is probably not the best material for this as it melts about 600°C

janeemarie 5 years ago

What size tank is this? For Christmas I am getting my husband all the supplies he needs to build a forge! This video and instructable has been an amazing help. There are a few things I’m not familiar enough with to eyeball though.

hydro8082 4 years ago

It appears to be a standard 10 gallon portable air tank that can be purchased at most hardware or auto parts stores

Oldprophet 4 years ago

Were did you get your ceramic board insulation?

bob_the_builder21804 6 years ago

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 6 years ago

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?

Kraeik 7 years ago

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.

AndrewW1977 7 years ago

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 7 years ago

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

https://www.amazon.com/gp/product/B000E62GRU

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 7 years ago

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 7 years ago

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.

AndrewW1977 7 years ago

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 7 years ago

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 7 years ago

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 7 years ago

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 7 years ago

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 7 years ago

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.

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