What Is the Difference Between Coal and Coke Fuel?

Blacksmith working over a large coal fire.

Have you ever wondered what makes coal different from coke? After examining the differences, you’ll appreciate how both types of fuel benefit the blacksmith.

What is the difference between coal and coke fuel? Coal is a shiny, black fossil fuel that contains impurities, emits smoke when burned, and produces less heat than coke. Coke is a dull, black byproduct of coal that burns hotter and cleaner.

Although coal is not a renewable resource, it’s trusted to generate electricity around the world. Coal is also a conventional fuel for industrial applications, such as the production of steel.

By the 1880s, most plants used coal’s byproduct, coke, to produce steel. Currently, most steel producers use pulverized coal, rather than coke ovens, to make their products.

However, blacksmiths still rely on coke as an efficient source of fuel for the forge. Coke’s properties significantly differ from those of coal, but both serve their purpose in blacksmithing and benefit master craftsmen.

Learn about getting started, blacksmith flux, important tools, project ideas, and more. You’ll find all my blacksmithing articles right here.

Producing Coke From Coal

If you want to forge with coke, you’ll have to heat bituminous coal first. Depending on the location of the mine, bituminous coal contains varying amounts of impurities.

High levels of contaminants negatively impact the metal with which you’re working and have an unpleasant side effect of toxic fumes.

If you want to produce premium coke fuel, purchase bituminous coal that has low sulfur and low ash.

Believe it or not, you can find excellent quality bituminous coal on Amazon. It comes in 50 pound bags and is already cut into 1 – 3 inch ready-to-light chunks.

Many blacksmiths encounter problems when shopping for quality coal. If a local supplier’s coal is loaded with impurities and is not worth purchasing, you may have to pay more for superior coal.

However, if you happen to live in an area that charges less for anthracite than high-end bituminous coal, you could try anthracite instead.

Anthracite is not porous like coke and is difficult to burn. It takes much longer to reach a suitable forge temperature, but if it’s all you can find in your area, it will work.

Ideally, you’ll want bituminous coal for your forge. (In case you don’t already have a forge, I tell you exactly how to create a simple, completely functional DIY forge in this article.)

For a detailed demonstration on using coal in your firepit, watch this video by Black Bear Forge.

Before you actually light the fire, be sure you’re wearing the proper protective gear such as:

When you start the fire in your forge with newspaper, it’s best to place coke from a previous burn in the center of the pit, but if you don’t have any, use small pieces of wood.

Around the center of the pit, place the coal next to the burning paper. As the fire burns, move the fuel closer to the center so that the pieces on the perimeter of the pit will carbonize and turn to coke.

Once the coal is coked, you can tell the difference between it and the coal. The porous coke is lighter than the coal, and when you stir the fire, you’ll find clumps of coke in the center of the pit.

How to Use Coke Fuel

Coke is a byproduct of bituminous coal. When coal undergoes a process known as destructive distillation, it converts to coke.

This process entails heating the fuel at a high temperature with no oxygen. 

The impurities and flammables burn off when coal changes to coke, and the result is a dull, porous substance with high carbon content.

Although it occurs naturally, most coke is produced by man. Currently, coke is most commonly used in iron smelting, steel production, and blacksmithing.

If a blacksmith heats bituminous coal to a temperature of 1,832 degrees Fahrenheit, the coal begins changing to coke.

As a fuel, coke has distinct qualities that are beneficial to blacksmiths.

New to the world of blacksmithing? Be sure to check out my Top 5 Beginner Blacksmith Projects.

Advantages of Coke As a Fuel

There’s a reason, actually quite a few of them, why blacksmiths prefer to forge with coke. Let’s take a look at the advantages provided by coke fuel.

Higher Forging Temperatures

When coal turns to coke in a forge, its temperature can reach 2,912 degrees Fahrenheit. This extreme heat is hot enough to melt iron and is ideal for blacksmiths.

Smokeless Fuel

Before coal becomes coke, it emits a harsh, dark smoke. On the other hand, when coke combusts, it burns clean. That’s a significant advantage if you plan on spending several hours in front of the forge.

Fewer Emissions

Many of the impurities and volatiles, including methane, sulfur, and carbon dioxide, burn off in the conversion from coal to coke. 

High Carbon Content

Since coke contains a higher level of carbon than bituminous coal, it’s more efficient to burn. Higher carbon levels mean that coke retains more energy from its plant debris origins. 

Center Glare Reduction

When a forge nears 3,000 degrees, it produces an intense, white light. The light will damage your eyes if they’re unprotected.

However, if you carefully work the coked coal into the center of the pit where the glare is brightest, you’ll reduce the glare and save your eyes.

Protecting your eyes should always be top priority. You definitely should invest in a quality pair of safety goggles with UV protection.

Understanding Coal

The Carboniferous period of the Paleozoic era was a period in Earth’s history where forests and shallow oceans stretched across the globe. The creation of coal is believed to have begun in this period. 

When flooded forests trapped algae and other forms of vegetation in the bottom of swamps, the material was forced deeper into the earth.

Over time, this organic matter slowly decomposed. Extreme temperatures, high pressure, and a lack of oxygen helped transform plant debris into coal. 

Five Levels of Coal

Although it looks like a rock, coal is an organic material. The carbonization process of coal is a very long one, but you can use coal at different stages of its aging process.


Although peat is not technically coal, it can become coal in ideal conditions.

The plant debris is only partially carbonized and is not as efficient for fuel as coal is. However, the peat found in swampland protects areas during flooding because it absorbs a vast amount of water.


In terms of age, lignite is the youngest form of coal. It is also more costly and risky to mine.

Lignite contains less than 35% carbon and has higher moisture levels than older types of coal. Due to its combustible properties, it can be deadly if improperly handled.

Sub-Bituminous Coal

Older coal that contains up to 45% carbon is sub-bituminous. Like lignite, it is brown, dull, and mostly used in electricity generation.

It contains less moisture, and when burned, it produces fewer emissions than lignite.

Bituminous Coal

With a carbon level of up to 86%, bituminous is the preferred type of coal for mining operations and blacksmithing.

It accounts for the remaining half of US coal production and is a significant source for energy in North America, South America, and Russia.

Bituminous coal is older still than sub-bituminous coal and is the predominant fuel source for steel companies, blacksmiths, and other industrial manufacturers. It is also often converted to coke.


Because it’s under intense heat and pressure for a more extended period before it’s mined, anthracite retains more energy than other forms of coal.

Its carbon level can be as high as 97%, but due to its expense, anthracite is not ideal for wide-scale energy production.

Some industrial manufacturers and blacksmiths use anthracite as fuel, but its most essential and beneficial use is in water filtration.

Here’s an interesting video on the history of anthracite mining in Pennsylvania.

Last Stage of Carbonization: Graphite

Although it is no longer coal, graphite is the final stage of carbonization.

Although graphite is not suitable for energy production or metalworking, it’s widely used in several practical applications. As a conductor, it is a common material in lithium-ion batteries.

It’s also a significant component in rockets and missiles because it has a heat tolerance of 5,400 degrees. Until recently, graphite’s most recognized use was in the manufacturing of pencils.

Are There Other Byproducts of Coal When Blacksmithing?

Another byproduct of coal that you may not find too pleasant is clinker.

Clinker is a hard, clumped mass that will clog up the bottom of your fire pit. It forms when bits of metal, impurities, and dirt collect under the burning coal.

Unlike coke, clinker is hard, shiny, and not porous.

When you find chunks of clinker in your fire pit, remove them. The irritating material will prevent the fire from reaching an optimal forging temperature.

Closing Remarks

Although there are several different types of fuel to use in your forge, bituminous coal is an ideal choice for forging with high temperatures.

Once you burn off the impurities and convert the coal to coke, the fire burns clean, and you won’t notice as much smoke or foul odors.

So, grab a bag of high-quality coal with few impurities and fire up that forge.

Don’t forget to read through all my blacksmithing articles for key tips and detailed info about this valuable skill and worthwhile hobby. Click here for more.

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I'm a hobby enthusiast with a real love for painting miniatures. I also happen to run this site and write the majority of its content!