Primitive Smelting

[chrisski]

I crushed up a couple of ounces of copper ore to smelt, pictured in the white cup with green dust that looks more whitish.  I roasted the fine green dust in a clay pot in the fire for a couple hours.  The next day I panned the ashes out, and was left with lots of black sand, which I guess is copper oxide.  I guess my next step will be to crush up some charcoal, mix it with the copper oxide at a 1:1 ratio, put it in a clay pot, and roast over charcoal and fanning the coals as much as I can.  That should create a reaction where the CuO and C are changed to CU + CO, or the charcoal and copper oxide turn to copper and carbon monoxide. 

Doing this off a couple of You Tube videos, and not much is available on the process, so any tips appreciated.  The video made it appear as if the copper should appear after the first burning, but later I found a couple more that said to mic the black ore with powder.  This does not necessarily need to be hot enough to melt the copper, but create the reaction to get the oxygen out of the copper oxide.

[Sonoran Dave]

When I found that half pound copper chunk last year, I did some limited research into primitive copper smelting to try and figure out how they did it. I couldn't find much either. Maybe try a library and look for a real book on smelting. The internet still has gaps in its collective knowledge base and you may have to go old school to find your answer.

Post your progress please. I'm fascinated by the subject and I hope you succeed. 

[chrisski]

I am trying to figure out how I want to do this next.  I do not want to spend 2 hours blowing a straw hoping to get the coals hot enough to melt, so I'm looking for a scrap computer fan to stoke the coals.  I've also looked at maybe using a Bunsen burner, but there's too much there to do in a reasonable amount of time.  I guess a marble sized piece of the black sand copper oxide would be way to much to melt with a Bunsen burner and I have 2/3 of a 3 OZ Dixie cup I want to try to smelt.  I'm unclear if a small propane torch would be hot enough.  Some of what I see makes it plenty hot, but other of what I read makes it hot enough only at the tip of the flame.  Oxyacetylene would definitely be hot enough.  Either of those gases are too much for what I want to pay for this. I may get a small smelter for Christmas. If I can scrounge up a fan and maybe a length of metal pipe for the air to go into the clay where the coals are before Christmas, I will give it a shot

You mentioned getting a book in the library.  I went to a small store today to pick up a book on gardening, and the store didn't sell any books saying there was too much stuff available on the internet and with how long they would sit on the shelf, the book would be outdated and non-purchasable.  Also seems that even our schools are moving away from textbooks as learning starts to migrate to the web.  I may have to add this to my YouTube channel once this is done.  With just being in books these kind of things are a dying art with no one putting a good how to video on YouTube.

[grubstake]

Get you some Map gas, its hot enough to do what you want. Grubstake

[Desertpilot]

I’ve seen a torch taken chacocite and when burned it created visible copper. Seen this at a mine down near Bisbee. I’m not sure how that worked but every piece brought out from underground did that. 

I agree old school smelting is a lost art on the inter webs.

Be careful if your rocks have high zinc content.

 

 

Edited December 2, 2018 by Desertpilot

[chrisski]

8 hours ago, Desertpilot said:

I’ve seen a torch taken chacocite and when burned it created visible copper. Seen this at a mine down near Bisbee. I’m not sure how that worked but every piece brought out from underground did that.  

I agree old school smelting is a lost art on the inter webs.

Be careful if your rocks have high zinc content.

 

 

What's wrong with a high zinc content?  I know there's iron in there, because there is magnetic black sand just like every other rock I've ever crushed.  The area the sample came from was a test dig for a manganese mine, but ended up at non-commercial values, so I suspect there's also Manganese.

I may have a separate project coming up that may justify using a torch, so if I get one I may try that.

[Au Seeker]

If you heat zinc and breathe the fumes which will happen at a little over 900 degrees you could get numerous health issues commonly know as "metal fume fever".

 

https://www.teck.com/media/Zinc-Metal-SDS.pdf

[Saul R W]

20 minutes ago, Au Seeker said:

If you heat zinc and breathe the fumes which will happen at a little over 900 degrees you could get numerous health issues commonly know as "metal fume fever".

 

https://www.teck.com/media/Zinc-Metal-SDS.pdf

Yep.  A lot of fellows have become very ill from welding galvanized steel with insufficient ventillation.  

[chrisski]

Definitely won't be stoking the coals by blowing through a straw then.  I'll definitely be doing this outdoors.  There's probably all sorts of things that can go wrong from burning the rocks, especially if smelting does become a hobby. 

Turns out one of the documents for where this ore came from lists it as a former Zn-Mn-Au-Ag-Cu-Pb mine, so there's a high chance that there's a bit more than trace zinc and lead in there rocks.  Guess I shouldn't be roasting this with a torch on a consistent basis.  Whatever I end up with, I'll probably take for an XRF analysis.

[Saul R W]

Also, the straw-for-bellows can itself be dangerous.  A single hiccough and the accompanying intake of breath (and super hot air) has done in more than a couple of glassblowers over the years.  

[chrisski]

Unsuccessful try with a MAPP torch.  What I ended up with looked a lot like what I started with.  There may have been a flake or two of copper visible under the loupe, -50 mesh,  and I did not get a picture of it.  I had expected to get about a teaspoon of molten copper, but I didn't.

I did three sets of burns. 

1) I mixed about two parts baked ore with one part powdered charcoal.  The first burn melted seemed like the flame blew most of the sand away, but left me with a about a dozen tiny pebble size pieces of black, with a couple specks of quartz looking mineral.  In the picture by the loupe (Middle), that pebble is pictured on the right.  For the under the loupe picture (Right) it is the black pebble that has white from reflections.

2) The second burn I put it in a deeper pot, and baked it, still one part charcoal by volume to one part baked ore..  Seemed like the crushed charcoal disappeared quickly, either burning up or blowing away.  I was left with a few more pieces of the black pebbles.  All these pebbles in both burns look like charcoal, but are harder, but still crumble to with finger pressure.  The bits of white glass were also present on this burn, and those were brittle.  This burn I cooked under the MAPP gas for 3 minutes and it was white hot, but didn't melt.  In the glass from the burn is where I say the copper in the glass under the loupe.

3) The third burn I took a rock with the original green ore and burnt it with the MAPP flame until it turned white hot and a couple of pieces flaked off.  Looks like burnt rock to me, possibly a fusion crust with the inner part inside.  This is pictured on the left.  Under the loupe picture (Left)  it is the browner of the rock.

I've got a third of the original crushed baked ore, but am not sure what my next step is.  I don't think I will be using the torch to melt anything.  If I go any more forward, I will move up to a smelter.  The torch just kicks up too much of the crushed ore.  When I try to heat the clay pot from the outside, it turns red hot on the outside, but the inside does not get white hot.  Even when I put the flame to the ore, it may not get hot enough for the reaction to take place for all I know.

[Saul R W]

You might also try adding lime to the ore prior to firing, which could give O2 and other undesireable characters a place to call home, and prevent them from recombining with your metal.  

Edited December 6, 2018 by Saul R W
Ha! Mr. Expert that I am, I just now almost caught my shack on wheels afire. I should know by now not to cook and type simultaneously.

[chrisski]

It may be the O2 is recombining with the metals.  I had not thought about lime, but I was thinking of Borax.  I need to read to see if it is a flux though.  I thought I saw it at our local prospecting shop a couple of years ago before it closed.  If I continue, I'll need to get away from the torch.  That just kicked all the smoke and debris and ash into my face as I was cooking it.  Not bad once, but I don't want to keep that up.  There is another local shop I may visit over the next few days.  Last time I was there, they just manufactured sluices and had a poor selection of other stuff.

Turns out Amazon kindle Unlimited has a couple of books on refining gold I'm going over.  I hope there's a chapter on fluxes.  These are geared towards jewelry.  The primitive smelting video that showed copper production had a the copper ore buried under grass sod blocks as the fire was fed under a few inches of dirt with a bellows.  I think you're right about not getting the metal to recombine with the oxygen.  Either that, or my charcoal I used for carbon was not the carbon needed to react with the oxygen in the copper oxide to take the oxygen out of the mixture.

I'm working across from a library for the next couple of days that has the best collection of Arizona Rock collecting books I've found in a library, so perhaps it will be there.

[Saul R W]

Borax is a lovely O2-keeper-awayer for forge welding.  It might work for your smelting, too.  Don't use the kind with detergents added, but rather pure sodium borate or maybe one of its kissing cousins, (di)sodium tetraborate.

[Desertpilot]

Slam some beers and watch this.

 

[Sonoran Dave]

I can visualize early man using the method in the video. 

Saul has it right though. Reducing atmosphere and heat from the bottom. The method in the video accomplishes both with the investment of some time and a bag of charcoal. 

Here is a video I just found after watching DP's. 

 

[homefire]

Real Charcoal gets AMAZINGLY Hot.  Hot enough to melt Iron if shot with air from the bottom or sides.    Even the air from a small vacuum cleaner can do the job. 

[wet/dry washer]

wit had a big pile of aluminum roofing sheets to melt. put large cast iron frying pan on iron wood fire, kept feeding the sheets into the pan. next morning lifted the pan, bottom of pan gone. lifted the aluminum slug out, there was the iron slug.

 

[Bedrock Bob]

A juniper fire and the blower from your drywasher works great. Getting the right amount of glass, salt and borax to keep it all from sticking to the crucible and not boiling over is the trick. 

[Edge]

On ‎12‎/‎5‎/‎2018 at 6:19 PM, Saul R W said:

Chrisski, you'll need a reducing flame, meaning the flame should be coming up from below, through a deep bed of hardwood charcoal or coke, so that the O2 has already combined with the fuel, and so that by the time the heat reaches your ore there is little or no free oxygen left to react with said ore.  It's very similar to the desired fire conditions when forge welding iron or steel (and similar, too, to conditions when welding with oxy-acetylene, Tig and Mig, except in those instances you're using shielding gas, either from tanks or rod flux, to prevent O2 from reaching the metal surface).

Anyway, figure out a way to place a deep bed of high-carbon, oxygen-consuming fuel UNDER your ore, and then feed air under pressure (your wife's hair dryer) from beneath the fuel, so the O2 is already otherwise occupied by the time the heat reaches the ore.  A deep fuel bed is critical to what you're trying to do.  If you're just blowing flame down from above or from the side,  you'll repeatedly end up with hot rocks, and ore that's more oxidized than it was when you dug it out of the ground.  It will take some experimenting to discover just how much air blast to use -- too much air, and your fire won't be a reducing fire, meaning oxygen will reach your ore, and too little air will mean not enough heat.

SOURCE:  Forty two years of hobby blacksmithing; BS, Technion, metallurgical archeology; split MS, Technion, metallurgical archeology, fluid dynamics engineering; 12 years consulting forensic metals engineer for the planet's premiere manufacturer of orange wannabe farm tractors; plus 18 million failed forge welds until I learned to do it blindfolded, one-handed and while smoking a pipe and chewing gum, also standing on my head, which might explain the baldness.

[homefire]

3 hours ago, Bedrock Bob said:

A juniper fire and the blower from your drywasher works great. Getting the right amount of glass, salt and borax to keep it all from sticking to the crucible and not boiling over is the trick. 

Juniper is nothing less the Low Grade ROCKET FUEL !  LOL   I Killed a nice little Pot Belly Stove with that stuff before learning what it was like.  LOL

[Bedrock Bob]

1 hour ago, homefire said:

Juniper is nothing less the Low Grade ROCKET FUEL !  LOL   I Killed a nice little Pot Belly Stove with that stuff before learning what it was like.  LOL

Indeed. If you have a leaky gasket or a gap that causes it to suck a stream of air it will puddle a spot in your stove.

I had a leaky window gasket that melted a piece of my stove when a juniper log rolled up against it. It gets wicked hot in a steady stream of air.

[chrisski]

Here is a couple of specks of dirt that may have a little copper in it from the smelt.  The white grain that has the copper in it is about the size of a period at the end of a sentence.  The pictures were taken with a cheap Chinese made USB microscope.  I don't know the magnification, but it is sure not the 1600X it claims. First picture is not that apparent, but at the bottom right up and down there's a little copper streak.

 

Edited March 29, 2019 by chrisski

[Sonoran Dave]

I like that first picture! I would hang that one on a wall. It's like... Picasso meets microscope.

It would be a dandy camouflage pattern too.