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The
forge hearth is the center of focus of the blacksmith's work. It is in the fire of
the forge that the iron is heated to incandescent red, orange, yellow and white
heats. For only at these highly elevated temperatures can the iron and steel be
made plastic enough to be shaped and deformed easily and without damage to their
granular structure.
Latest Update: Monday September 16, 2019.
What is a forge?
The forge is the hearth that the fire is kept upon, or inside of, for the purpose of heating the iron. The forge provides a safe fire resistant structure in which to keep the fire, and to which a source of air blast can be piped to increase the heat of the fire. Most modern shop forges incorporate a chimney structure to remove smoke from the fire, out of the shop safely. The blast of air raises the heat of the fire in the same way as blowing softly on a small flame to help light a campfire. Click the links in the navigation bar at top of page to see examples of blacksmith's coal forges; on the Coal Forge pages.
The blacksmith's forge has remained similar in design and purpose for millenniums. Some of the differences being in the materials we now use to build our forges and the source of air supply and delivery. Despite its modern look, the modern forge works exactly the same as those of its predecessors.
Showcasing now 17 different blacksmith's coal forges on 13 pages. The Coal Forge series offers a look at how other smiths from around the world, build their forges. To visit the Coal Forge pages, click on the links in the navigation bar at the top of this page.
The Coal Forge pages have several purposes:
What fuels are used for the fire?
Charcoal was the original forge fuel. Blacksmith's charcoal is made by a process of distillation in which wood is heated hot enough to burn, but starved of oxygen - causing most of the compounds in the wood to be driven off in the form of vapors or smoke - leaving carbon behind. Before the industrial era this was accomplished by stacking logs in a pile and burying under a mound of dirt. A small fire was built at the bottom of one end and a hole opened in the top of the mound to vent the vapors or smoke. The air supply was restricted to allow the fire to burn hot enough to literally char the wood into 'coal', but at the same time starving the wood pile inside the mound from getting enough oxygen to burn completely. The idea was to put out the fire after the wood was converted to charcoal. After the burn most of the wood was recovered in the form of charcoal with only minor losses due to burning wood that was closest to the fire. Visitors to this website will need to search elsewhere for instructions on making charcoal.
Barbeque charcoal as forge fuel. A beginner might ask the question: "can I use barbeque charcoal?" The answer is no, barbeque charcoal does burn red hot, but barbeque charcoal is dirty and produces too much ash and does not allow the smith to work efficiently. Barbeque charcoal is made from wood chips and/or straw and clay or some other filler material, pressed together to form brickets and heated to drive off volatile matter - thus creating small convenient brickets of charcoal for barbeque use. The filler content and the low grade materials used in making barbeque charcoal, creates a tremendous amount of ash. The high ash content, along with the high price of barbeque charcoal, makes this fuel prohibitively expensive and unsuitable for use by blacksmiths.
Coal. Between approximately the 15th and 19th centuries, blacksmiths gradually began the change to coal as their primary source of forge fuel. Not all coals are suitable for forge fuels, and the lack of access to a source of good coal and the lack of success with coal slowed its adoption as the primary fuel for blacksmiths. Even today blacksmiths must be very picky about how and where they obtain their coal, and most smiths locate good sources by word of mouth. In some regions of the world, coke is easier to obtain. Under construction.
Coke. Coming soon. Under construction. A new section (including lots of photos courtesy of a friendly coke supplier) will be added here soon.
The Forge Design pages (now numbering 9 separate pages and more material will be added soon) offer lots of ideas to help in the design and construction of good custom built forges. Note that when this page was originally written, I was counting the Forge Design pages together with the Coal Forge pages. This has changed and I know count the Forge Design pages as a separate source. What the reader will find here is lots of pictures of real blacksmith's forges - built by professional and historical blacksmiths from around the world. The style and method of constructing the shop forge is a matter great consideration and individual preference of the blacksmith who will be using it everyday. A blacksmith cannot use 'just any forge'. Placement of the fire, chimney, size of hearth, height, and materials and construction considerations are discussed. This series has become a great companion resource to The Coal Forge pages.
Time and again, amateur smiths often build their forges with little or no knowledge of what they are doing. Worse yet, they usually build another forge to replace the first failed attempt, and again they fail to learn from previous mistakes. The Forge Design pages - and the Coal Forge pages- were published specifically to help new smiths start out with the best forges possible.
The smith that fails to understand basic fundamentals of forge design will ultimately fail to build a good blacksmith's forge. Let me give these readers a hint. Learn how the professionals build their forges - look at what the best blacksmiths did to design the most practical forges for their shops. Forge design must give careful consideration to the work that will be encountered throughout the life of the forge. There are very important forge design aspects that must not be overlooked - or the smith risks being forced to tear down the original forge to build a properly designed forge. Do the job right the first time, and it won't need doing again. The Forge Design pages were written to help the new smith better understand as many aspects of forge building as possible, and to help the new smith do the job right the first time.
The Fire page links to articles that help the new smith learn how to use a blacksmith's fire. After reading the Fire pages, an amateur smith or beginning smith will have a better understanding of how the fire is used, and and be able to troubleshoot problems he may be having with his fire.
Lighting the Fire was written for beginners. This page written exclusively for beginners, details several different methods of lighting the blacksmith's coal fire. Look for a few photos to be placed on that page soon.
Using the Fire describes the proper maintenance and control of the blacksmith's fire to heat the iron for forging and welding. Photos will be added to this page a few at a time as I have time to shoot them. Heats and colors are described on this page along with fire tool use.
What about natural gas and Propane?
Blacksmiths today now have access to gas-fired forges and furnaces as well as coal and coke forges to heat the iron. Gas forges offer the convenience of not having to worry about where to buy good blacksmithing coal. Gas forges are not as hot as coal forges and take longer to heat the iron to a forging temperature. In all cases the lower heat value of gas means longer heat times and more oxidation. However the size and capacity of the gas forge allows a much larger number of straight un-worked, or nearly straight bars to be placed in the fire at one time, and therefore can heat more un-worked bars over a longer period of time than the coal forge. Many small companies that produce small forgings - are more likely to have a gas forge than a coal forge - because the gas forge can heat many small bars at once, and the gas forge does not require the workers to have large amounts of training or experience. On the other hand the and the coal forge is still king when higher heats on larger and heavier bars are needed, and fewer bars are to be heated for work, and for heating work of more complex shape which cannot be placed inside the limited interior area of the gas forge. Each type of forge (coal or gas) has its advantages and disadvantages, and this is why each shop must choose what type of setup works best in their situation. Many shops employ both gas and coal forges and use them each for specific tasks such as; coal for heavy bars, and a gas for large quantities of small work.
Most gas forges never get up to welding heat.
Contrary to what most hobbyists are claiming today, most factory-made gas forges cannot reach welding heat. Don't be fooled by the claims of amateurs that they forge weld all the time with this or that forge. Most amateurs are simply boasting of being able to do something that they have never actually done. Most factory-made gas forges cannot reach welding heat, and the few that can, will heat the iron much more slowly. During the last 25 years, a new welding flux was introduced specifically for allowing gas forges (those forges that are actually capable of reaching welding heat) to be used for welding. This special flux is formulated for the increased scaling that results from longer heat times when using the gas forge.
The lower temperature and slower heating associated with the gas forge is actually helpful to most beginner smiths and those with poor fire skills because, a cheap gas forge will not heat the iron to a sizzling white heat- suddenly destroying the iron. Instead the iron will waste away (slowly burning) in the gas fire over a long period of time, but the inexperienced smith need not worry about suddenly destroying his iron by accidentally leaving it in the fire too long. On the other hand...
Some gas forges CAN get hot enough to fire weld!
There are some homemade and custom designed gas forges that can reach this higher heat. If the reader is going the gas forge route, I recommend visiting Ron Reil's website to see how to design the hotter custom-made forges at http://ronreil.abana.org/design1.shtml . Ron has compiled a large collection of designs both of his own and those sent to him by friends. Lots of designs of burners, insulation, most are inexpensive.
Special fluxes needed for fire welding with gas forges.
Since gas forges will take longer to heat iron, more oxidation will develop during the extended heating period. Special fluxes are used to deal with the additional scaling which results from this oxidation. Centaur Forge (www.centaurforge.com) sells these fluxes.
Latest Update 16 September 2019.
The author can be emailed at address in picture below:
December 1999