Inventions & People of Cast Iron History

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Sara, here

This was a much, much, much longer post originally. Which means I should cut it down, so what was a multi-page piece now becomes something shorter. I’ve heard our attention spans are waning, so…now you get information in snippets here, too. I want to talk about some of the inventions and the people (other than blacksmiths, which are their own topic and post) who made cast iron possible in the past and, consequently, into our current day.

The blast furnace was supposedly first invented in the areas of Sweden, France and Belgium between the 1100’s – 1300’s. For the first time in history, fires could be made hot enough, and sustain enough heat, for a proper length of time to get the iron blooms up to 2800 degrees and stay there long enough to be poured into molds. The process to create efficient furnaces that could produce more slag-free iron was refined first in Spain, and later in Austria and Germany, where they created taller furnaces with air power provided by water wheels and other mechanics.

Higher quality iron was pumped in greater quantities from these furnaces, which was a big deal – less brittleness, less screw-ups…you get the picture. Suffice to say the 15th century the blast furnace revolutionized how iron was heated, melted and formed. Melted iron means a great many possibilities could now be realized. And realized they were!

Still, for all it’s meltingness (not a word, I know), the iron needed to be handled by hand until the process was mechanized. The workers who originally had a hand in both making and experimenting with hot iron (thereby paving the way for today’s current iron and steel) are lost to posterity (or at least, the information about them is rare). These iron workers were called puddlers.

Puddlers were usually great bears of men – they had to be, to withstand the enormous heat that they stood by all day, pulling the paddles through the molten metal to create purer blooms of iron against slag. Most puddlers were dead by the age of 40!

To puddle, the pig iron was smelted (heated) in the blast furnace until it ‘boiled’ and then the boiling iron was moved about, or “puddled” by the puddler to help remove impurities from the iron. The stirring would continue until all the oxygen was also removed, apparent to the naked eye when carbon monoxide stopped bubbling to the surface and could be formed into balls. These balls were then shingled (meaning hit with a shingling hammer) leaving a “bloom” now shaped into a brick of iron usually 5” x 5” x 36” in size. After rolled through the mills, the squashed bar was re-heated until it reached the hoped-for grade of iron/steel, even though these earlier smiths had no idea they were making cast steel if and when it happened. The puddlers did, however, have a hand in trying to create steel by cooling the hot metal at different rates to see what might happen. Pretty cool, right?

Another piece of the puzzle to creating today’s cast iron is that the blast furnaces, once developed by more modern foundries in the mid-1800’s, were heated with minerals instead of wood (forests already, especially in Europe, being greatly depleted thanks to the Industrial Revolution). In America, the fuel called ‘stone coal’ or anthracite coal, was used in the blast furnaces. While anthracite was hard to burn, it was inexpensive compared to charcoal and less frangible, which means it was not as molecularly brittle as regularly charcoal and was less likely to back up and clog the chimney. Because of this, bigger blast furnaces could be made, and the blasts of air pumped in became hot blasts (instead of the previous cold), hugely affecting the iron market and making it ever easier to make and less expensive to sell.

Once the American railway system came into play, they demanded cheaper iron products that were hardier than the original wrought iron rails (originally made by blacksmiths, expensive, and usually broke often). With new types of furnaces (the Bessemer) sweeping the nation and the world, as well as the use of bituminous coal (turned to coke) for heating, suddenly the original tall blast furnace and its anthracite heat source were rendered obsolete. It all happened relatively quickly, if you think about it.

I also want to dip my toe into another terminology piece of the puzzle here and discuss the “Three F’s of Iron” – and no, I don’t mean the ‘f-bomb’ you drop when trying your hand at an anvil at a re-enactment and bang your thumb. The 3 F’s are as follows: Forges, Furnaces and Foundries.

Forges came first – these are the blacksmiths who beat the metal and make wrought iron, and heat and curl and create, in this day and age, beautiful single pieces one by one with a small bellows and fire.

Furnaces next – the blast furnace, that is, which is where iron could finally be completely melted and new possibilities in terms of molding, heating, cooling and even iron quality became possible

Foundries – with the Industrial Revolution, foundries took on the bulk of the iron work, thanks to the invention of the Bessemer and use of coke fuel. Foundries today make all the cast iron pieces that are modern-made.

Blast furnaces remained in use for at least 100 years after the Civil War, but they primarily turned out the more brittle pig iron for forges/blacksmiths, and also as a supplier of the pig iron as one of the additives to the cast iron make-up. Blacksmithing trades became far less necessary. The mass production ability of the gray iron (and later cast steel and ductile) and the molecular structure and capabilities of these two made wrought iron and their smiths a commodity of the past. However, we shouldn’t forget how incredibly linked each piece of the historical adventure in iron truly is.

Without all the pieces leading up to change and inventions, there’d be no Industrial Revolution, and certainly no great cast iron piece for your morning eggs. Pretty amazing, don’t you think?

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