It’s not a “weird” question, but it might not be “boring.”
Anyway, does anyone know where I could find a good illustration of an early Copper-smelter design? And I mean like “Pre-bellows” early.
And also…all the sources I’ve found online noted how both purified Copper and “slag” were/are produced in the smelting process…but, what exactly do the Copper and slag look like when they’re pulled out of the smelter?
Well, thanks for your time,
Ranchoth
A local hsitorical group once demonstrated this. I didn’t have a camera along, so there are no pictures for me to show you.
It looked like this:
Dig a hole in the ground about three feet across and a foot or so deep.
Build up a thing like an inverted funnel above it. You use clay, and build up a large base. Then you build the funnel on top of this . The hole down the middle of the funnel is about as three feet across, just like the hole in the ground. Your funnel needs to be a good twelve to fifteen feet high, and still a bout a foot thick when you get to the top.
One one side of the base of the funnel and above ground, you make a hole about a foot across that goes all the way into the bore of the funnel. This hole lets in air for the fire.
Fill the funnel with copper ore and charcoal. I don’t know the proportions, and it would vary with the quality of the ore anyway. The guy doing the demo commented that this method really only works with high quality ore - lots of copper, relatively few impurities.
Light the fire though the air hole in the bottom, and let the whole mess burn out. You can add more ore and charcoal through the top while the fire is burning, but after a while the funnel will be clogged and won’t burn hot enough to purify the copper.
This thing works by using the fire in the high funnel to generate a draft. The hot air from the fire rises and creates a draft. The higher the funnel, the stronger the draft and the hotter the fire.
The guy only had a little ore, and apparently it was of poor quality. The smelted copper looked like little dark brown metallic globules fused into clumps. There wasn’t much of it, and I suspect that if there had been more it would have looked more like a large lump of brown metallic stuff instead of being just drops that collected up.
The slag looked like black ash. It was hard and in clumps that looked like you had made charcoal from termite eaten wood - imagine charcoal riddled with zillions of little holes.
To make the smelter more efficient, you would set it in a hollow - sort of off the side of a small hill. The top of the funnel would be above the top of the hill. A breeze blowing across the hill would create a lower pressure at the top of the funnel and make the draft stronger. You arrange things so that you can walk up to the top of the funnel so that you can drop more charcoal and ore in the top (which would be a nasty job when the fire is burning.)
You dig your smelted copper out of the smelter through the air hole at the base. If you are good at it, you can load at the top and unload at the bottom and be in continuous production for as long as you can supply ore and charcoal.
Danke shoen…BTW, were the purified Copper and the slag “attached” to each other, somehow? Or was everything just piled together at the bottom of the smelter?
Pretty much just a mess at the bottom of the smelter. Lots of ash from the charcoal, lumps of slag and a couple of little lumps of copper. If I remember correctly, the copper seemed to have fallen through to the bottom of the mess. Then again, there was so little copper that it would be hard to judge if that is always the case of if the little bit just happened to fall there.
The copepr was seperate from the slag and the ash.
You might be able to find some stuff on the historical metallurgy site (follow links). I recall there was a Swedish group that did smelting and casting of replicas.
And save yourself the sore muscles and get a hand-crank bellows. The ancient smelters were in much better shape and were used to pumping the air bladders for hours on-end.
This site (which I coincidentally found yesterday …) has some good info. on early copper smelting, where and how it was done, what ores were used, etc.
http://www.unr.edu/sb204/geology/smelt.html
Here’s the simplest method: