Coal Forges vs Propane Forges for Blacksmiths by David Robertson

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Coal Forges vs Propane Forges for Blacksmiths
by David Robertson

Which forge is right for you if you are starting out as a blacksmith.

Coal Forge
Coal is the traditional fuel and forge for the blacksmith. Originally using charcoal blacksmiths switched to coal as the available timber had been used up in charcoal making. Coal and charcoal fall into the solid fuel category of forges.

The design of a coal forge is very simple and can easily be made by someone starting out. In general a coal forge is a table or pan shape roughly 2 feet in diameter (larger sizes for larger work) with a hole in the bottom about 3 inches in diameter. This hole has a
grate in it to prevent the coals from falling through.

A controlled air blast comes through the grate and fans the fire above. In better designed forges the hole is in a basin or trough shape formed out of cast iron. This is called the tuyere or the fire pot. This allows a deeper bed of coals under the steel that is to be
heated.

The air blast can come from a set of bellows, a hand crank blower, or an electric blower. Each one has to be able to control the volume of air flowing through the coals. The connection from the blower to the hole with the grate above it is a Tee connection. Think of the Tee on its side --| the air comes in from the side. The bottom is capped. The top leads to the grate and then to the coals.

Many blacksmiths start with a break drum forge. Which is just a small automobile brake drum supported on legs with sheet steel on top to form the pan. The brake drum is set into a whole in the sheet steel so the steel is level, with the brake drum protruding below it. Then use a vacuum cleaner blowing air, or a hair dryer as your air source. Not ideal and they will eventually burn out but will work to start.

I prefer a sliding gate to control the air flow. This way the motor just runs and you slide the gate to the desired position for the amount of air that you require. You can develop very good sensitivity this way.

This type of coal forge is very versatile. You can put almost any shape and size of metal into the forge and cover it with coals to get it hot. Very useful if you are working large odd shaped pieces.

Bennefits of the coal forge:
Most versatile for heating many shapes and sizes of steel.
Coal burns hotter than propane. Softer steel easier to work.
You can easily forge weld in a coal fire.
Easiest forge to build.

Disadvantages of coal:
Finding a source of coal.
Sulfer smoke when starting a coal fire nasty for lungs and neighbors.
You can easily burn your steel since it is so hot.
General dirt and mess associated with coal.
Difficult fire to learn how to maintain a constant heat.
Needs cleaning out every few hours. This depends on the quality of your coal.
Takes a long time to get up to working temperature.
Take a long time to cool down and make sure the fire is out of all the coals.

Propane Forge
Many blacksmiths have opted for the convenience of a gas forge. These are small insulated boxes with a propane burner going through the top and is directed into the chamber. The propane mixes with air either added by a blower or sucked in with the stream of gaseous propane.

The burner keeps running as the forge is in operation and temperature is controlled by adjusting the amount of propane that flows into the chamber. The box has doors either end or on the side to allow access for the steel bars.

The main catch with a propane forge is that everything that you want to get hot has to fit inside the box. Not as versatile as a coal forge, but there are other advantages.

Propane Forge Advantages:
Easy to run. Just set the pressure and you don't have to fool with it at all.
The fuel is easy to get at many gas stations, and relatively cheap.
Cleaner no smoke or coal dust around.
Takes up a smaller space.
Quick to start only a few seconds to fire up.
No cool down time. Just turn gas off and safe to leave.
Steel doesn't burn in a gas forge. Usually

Disadvantages:
The biggest disadvantage is everything has to fit inside the box!
Runs cooler than coal. Takes a long time to heat larger bars.
More difficult to forge weld in but possible.
Difficult to build without a manual or plans.
Working with a pressurize flamable gas, requires extra safety precautions.
Creates a more generalized heat than the spot heat of coal.

So You can see my preference is actually for a gas forge. I do use both and started with coal. The ease of use and the cleanliness sold me on gas forges, but when I do have large pieces or complicated shapes the coal is better.

No matter which heat source you use, it is the quality of work that is important.

Author's Biography:

David Robertson has been an artist blacksmith for over 20 years. He devotes his time to

educating people on blacksmithing tools and techniques. For more information on