How did ancient civilizations make ovens so hot that they could melt metal without the kinds on materials we have today?
In: Engineering
If you make a campfire out of some branches out in the open, there is a limit to the amount of heat that will be produced, which is far below the melting points of metals like iron or steel.
However you can alter the way you build that fire to heat it up…
To start with you can enclose a fire and turn it into an oven, which contains the heat and prevents it radiating away in every direction.
You can also add forced airflow – by purposely blowing air into the fire you are adding extra oxygen to the fire, which lets it burn faster and hotter.
You can also control what you burn to get a more efficient fire – using charcoal for example will burn much hotter than normal wood (charcoal is a form of wood that has been slowly heated to remove any moisture and carbonise it).
Add these things together and you can create a fire hot enough to work steel.
Iron Prills – https://www.youtube.com/watch?v=DyGLE0usN_I
Precursor: Forge Blower –
* with bricks and bellows you can create a fire hot enough to melt the melts ancient peoples used, such as bronze
* you don’t have to melt metal to work it, iron, copper and bronze can be worked after heating, gold and silver can be worked cold, and most metals can be sintered
You can make a something capable of melting iron out of clay you dig up locally and basic fuel, like coal. It’s not difficult. You just need proper airflow.
Also, to work metal you don’t need to melt it. Just heat it until you can work it with a hammer and tools.
That’s why it’s such old knowledge. It’s what let us get to the point we can melt materials with a much higher melting point,like tungsten.
It progressed over time
Early copper was cold worked, aka not melted. Then someone figured out bellows and made a kiln that could melt copper allowing it to be cast and then worked. Once you can melt copper you can also melt tin so now you’ve got some bronze which is harder than copper.
Iron was the hard one. Without coal you can’t really liquify iron and make proper steel so ancient cultures relied on clay bloomeries which would give you a blob of iron and slag that needed to be worked to beat the slag away and give you decent iron. Early iron would have been comparable or worse than the bronze of the era and it wasn’t anywhere close to even basic iron that you’d get today.
Making a really hot fire doesn’t require modern technology. That’s all you’re doing when you’re working with metals or building kilns to fire pottery – just making a really hot fire. It’s perfectly easy to make a fire that’s thousands of degrees with just wood or coal. All you need is some structure to contain the heat (brick, ceramic, stone…etc), fuel, and some way to blow oxygen to get the fire really hot and keep it hot. These are all things that require no modern technology whatsoever.
Clay and stone are *really* hard to melt. Copper, tin, bronze, iron, gold, and silver (common primitive metals) don’t have the highest melting points compared to other metals, and some melt at rather low temperatures (relatively speaking). Take a fire in a carefully shaped furnace made of clay, blow in a significant amount of oxygen (you can make a good bellow fan with a few sticks, some thread, some bark, and more clay), and you can make a furnace that gets hot enough to melt metal.
It’s really not all that hard. Finding the material’s actually harder, but we did that too.
Thank you everyone for such an insightful discussion!
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