Annealing Copper (or Silver) Without a Torch

I was responding to a comment from Sandra on my "Power of Money" post, and a thought occurred to me: Do you really need a torch if you're only annealing metal, and not intending to melt it? If not, what kind of heat source would someone already have in her home that she could use to soften  metal? Well, duh, I thought, how about a gas or electric range?

Electric Range in "Goldenrod" ca. 1975

The melting point of copper is 1982.21°F, or 1083.45° C. (Sterling silver is 893°C). Gases used in torches, such as butane, propane, MAPP and acetyline produce flames with significantly higher temperatures than this, which can melt copper (although because of the heat dissipation qualities of metal, and other factors, butane is not very effective, because the flame often isn't hot enough to overcome the dissipation--I've never been able to melt copper with a butane torch. I've also not been able to melt heavy gauge copper (like 16 gauge wire) with propane, which is why I switched to MAPP). Silver is much easier to melt, as the melting point is a little lower. You can melt smaller gauges of silver wire with a butane torch (I didn't have any luck with gauges heavier than 22 though using butane. I kind of think butane is a joke unless you're lighting a cigar. In which case I'll be in the other room with the window open.)

The element on an electric stove, set on high, is somewhere in the neighborhood of 550°C. A Bunsen burner produces a flame of about 1570°C. Natural gas, typically used in gas stoves in the United States, is about 1950°C on room air. (The effective temps of these flames apparently can be lower than this in real-life situations--flame temperatures quoted in data sheets and such refer to "perfect" conditions where no heat loss due to environmental factors is assumed.) Lightning, by contrast is 30,000°C. You should stay away from lightning.

I myself have an electric range (pictured above). I thought I would see what the element set on high would do to a 22 gauge copper disc.

I placed my copper disc on the cold burner,

cranked up the burner to high and let the disc sit there for a while. I dunno, 10 minutes?

It turned a little reddish. Another larger disc I did before was glowing dark orange, maybe I left it on there longer? Or maybe the other disc was a thinner gauge.

I let the burner cool down and removed the disc with my tongs. I ran it under cold water to make sure it was cool enough to handle. You will have sooty fire scale on it which will need to be removed with a pickling solution. You can use a mixture of household white vinegar and salt for that--just pour some vinegar into a little cup, just enough to cover your metal, put about a 1/2 teaspoon of salt in there, toss your metal in, swirl it around a bit and let it sit for 15-20 minutes. Then rinse it off and rub some baking soda on it to neutralize it, and scrub with steel wool. Should be good to go then. (The salt is important, the vinegar alone doesn't seem to do the job.) No pickle pot needed for this procedure! This is low tech stuff for us working poor.

The heating from the electric element did indeed soften the copper. Not as much as with a torch where you get it glowing bright orange, but I could bend the disc with my fingers whereas before I could not. It took the texture from my half crown coin easier than non-annealed metal. (See top photo). Obviously, this will work for wire too. Many intricate wire projects are much easier to do with annealed wire. (I have tried annealing nickel with my MAPP torch, to no effect. It did not noticeably soften it. Annealing red brass, which I prefer to yellow brass, produces a pink discoloration, from drawing the copper content to the surface, which I have never successfully been able to remove, even with commercial pickle, so I don't recommend annealing either of these metals.)

You should be able to get it even softer if you have a gas range, as the flame is much hotter than an electric element. You should be able to get it glowing orange. (Always be careful with flame and heat--even metal that doesn't look hot may still be very hot and burn you.) You will need some long steel, insulated tongs or pliers for that, something with a good gripping tip so you don't drop your metal, and insulated because the heat will travel to the handle and possibly burn you.

You might even be able to make a sterling silver headpin in your gas stove flame, although it would be challenging because the flames are oriented vertically. If you try it, you'll know what I'm talking about. If anybody has ever tried that, tell us about it!

So you see, all you torch virgins out there, you can still anneal your metal to an extent for stamping and texturing, even if you don't yet have a torch. Or even a gas stove.