Gas Forge Build 5: Intial Burn

Here have inserted the burners and tightened the collar screws. The flare tips are sitting up in the insulation about 1".
I placed to hard firebricks inside the bottom of the forge. This will prevent the ceramic blanket from compressing under the weight of whatever steel may go in. It also will keep the borax off the bottom.

I expect to replace these bricks from time to time, so they are not cemented in place.
With this arrangement the gas supply hose can come to the front or go to the back. After some consideration I think the hose would be best coming off the back of the forge.

This will give you an idea of the initial position of the torch inside the adpater. The torch can be slid in and out to tune the burner.

Additional notes: Stuff some scraps of ceramic blanket in the collar around the burner tube. This will prevent heat from escaping and avoid the chimney effect where hot air is drawn into the burner.

Open up the door to let some fresh air in and start it up.

Using a hand-held propane torch I lit the burners and cranked up the gas. The initial burn is quite rich. The large yellow flame is indicative of unburnt fuel.

After a few minutes I shut it down. Yes, It gets very hot. I don't think I'll have any problem forge welding in there. Some tweaks to do on the fuel to air mixture, but satisfied with the build so far. Stay tuned here for updates on the fine tuning.

Other Things of Interest

If your burners are running rich you can shoot some additional air into the intake to improve the fuel-air mixture. Remember we need about 1:100 fuel to air and that's a lot of air. If a burner is running rich, the additional air will make it more efficient and save you on LPG. The correct ratio will also reduce the carbon monoxide (CO) output of the forge. CO is bad.

LPG vapour is relatively safe and needs the right amount of air to burn. Unlike gasoline where combustion is possible with a wide range of mixtures, LPG needs the ratio to be just right

CO Detector
It's highly recommended that you get a carbon monoxide detector for your shop if you are going to forge indoors. CO is colourless and odorless and poisonous. Outdoor forges are ventilated and CO buildup is normally not an issue.
Storage of Cylinders
Legally in my locale (may vary by juristiction) propane is not to be stored indoors.

As per the Propane Storage and Handling Code, no propane cylinders may be stored or used inside any structure unless specified in the code, and shall not be stored or installed under any fire escape, stairway, or ramp used as a means of egress form a building.

This means your tank needs to be outdoors.

Orientation of Cylinders
The normal 20 lb BBQ cylinder must be stored and used in the upright position. The vapour is meant to be in the top of the tank. If the tank is on its side, there is a risk of liquid coming out of the tank's pressure relief valve or the main valve. One drop of liquid will vapourize to 270 times its volume. When mixed with enough air, this can become an explosion hazard.

Vapourization Rate
In cold winter areas this may become a problem as the low temperatures may prevent the vapour from boiling off inside the tank. The rate of boiling is a function of the temperature and surface area where the liquid is exposed to the ambient temperature.

Hose Protection
If you are concerned about accidentally hitting your gas hose with a super hot piece of steel, you can make a leather wrap for the hose. Optionally, you can buy a stainless steel hose braid to cover the hose or use foil for that matter.



  1. Are you happy with this forge? I am preparing to build one like it and would like to know if i need to make any adjustments to your design. Thank you for sharing your valuable knowledge.
    Tim in Kansas

    1. I am very happy with the forge. I am doing some forge welding of cable right now. Works great! I find that one burner is often enough. I shaped a piece of firebrick and set it inside the effectively shorten the chamber. Then use the front burner.


  2. Hey Dan - Quick question on the tank size. If I went with a 10 gal tank, would 2 burners still be sufficient? I'm getting ready to build this baby. Thanks!

    1. I'd think a 10 gallon tank with 2" of blanket would be fine. With the 5 gallon two burners is a bit overkill as far a heat goes. Having two burners is useful for evening out the heat.

  3. How long you burn with one tank of gas

    1. I haven't ran through a full tank at one time. The fuel consumption would be based on a bunch of factors. Most of the work I am doing with only one burner running. I'd say approximately 8 hours of single burner forging.