I am new, in a class, and struggling to anneal a sheet of 14 gauge
copper that is about 10" x 10". I first heat it with another student
and 2 torches. It looked glassy and the color changed, but not fully
annealed. Teacher felt because the edges were larger than the rocks
I put in the pan. Fine. Did some hammering and tried to anneal
myself, alone with one torch, laid it directly in the pumice, and
still not even near annealed…sigh.
Can anyone give me some suggestions, please? I thought about taking
it to a friend who has a foundry or to a machine shop, but I need and
want to learn to do this myself, of course.
Hi Brenda. Copper is fairly easy to anneal, if you bring enough heat
to it. If you’re using the small torch tips that jeweller’s use then
you just don’t have enough heat. If you can get a #4 or better
oxy-actelene tip would work, or use a propane torch head and MAP gas.
I like using a piece of plate steel (1/4" or thicker) on top of fire
brick to rest my piece of copper on. I find the steel holds the heat
and reflects it back into the copper, which for me allows better
control over the heat build up. With the size of copper you have to
fully anneal will take a bit of patience. The idea is to try and warm
up the whole piece at the same rate, do this by slowly moving the
flame around. The copper will go through colour changes, greens,
blues and black, you want to reach the point where the copper is
beginning to glow red. Because of the thickness you would want the
whole piece at that temperature for at least a couple of minutes. If
it glows redder, no problem, just don’t let it get past orange hot.
When you have heated it long enough, remove from heat and the steel,
you can water quench, quench in pickle (don’t breath the fumes) or
air quench. All work except by quenching in pickle saves a step and I
find cleans the metal quicker.
That’s what I would do if I only had a torch available, I would
prefer using a forge. You could build a temporary one by stacking
firebricks in an oven shape and using a tiger torch for your heat
source. Either way hope it works out for you, let me know how it
goes.
That is a monster piece of copper. A kiln would be better to heat
that piece up.
If you do have to use torches I would suggest that you surround the
sheet with fire bricks, and then heat your copper to dull red, or
even a cherry.
You can then let it cool, or as it’s copper you can dump it in
water, either way it will be annealed.
My teacher taught me a trick that was taught to him by someone here about when to tell when a piece of metal was annealed, the flame
from your torch changes colour… and it works really well. In this
instance with such a large piece of copper it might be impractical,
but it’s a good technique worth sharing.
Do you have some extra to cut into a smaller piece. Much better minds
than mine will respond to this, but practice small first. Get some
Scrap copper, 2+ inches from a plumbing contractor. Scrounge the
metal, my point being practice and learn to watch how the metal
responds. By the way, that is a hefty piece of metal, don’t know what
is available for heat, but if needed and cost effective, rig up a
stand to position two plumbers torches for more heat. Be careful
though, this metal is know to capture a heart or two… it was my
first love. enjoy
Can anyone give me some suggestions, please? I thought about
taking it to a friend who has a foundry or to a machine shop, but I
need and want to learn to do this myself, of course.
I tend to think “old school”. For something that large, try using a
el cheapo BBQ grill and a hair dryer to excite the charcoal. That
should get you to annealing temps. A lot of the great metal art of
history was done on charcoal fire pots…
Brenda, For a 10 x 10 inch sheet of 14 gauge copper you are going to
need a BIG torch (or two as you already tried) with as large a tip
as you can find to make the largest, and bushiest flame (i.e.:
reducing flame to minimize fire scale) that you can manage. You CAN
work the flame over the entire piece in increments, but you’ve got to
get it up to cherry red heat before it’s annealed. The whole piece
doesn’t have to get there at once, as I said, it can be incremental.
But don’t let any areas between cherry red spots exist or you’ll have
metal that is partly annealed between unannealed spots. Make sure
you quench the sheet in water while it’s just glowing or at high
black heat. If you let it air cool, the crystals will regrow and
you’ll lose a significant portion of the annealing. You’ll need a
good sized pickle pot in which to simmer it after. Have fun. Copper
is a very cool metal. All my students learn the basic soldering
joints in copper before they move onto silver or other metal.
If you can successfully solder copper you can solder silver, etc.
You need a bigger torch. When we anneal pieces that big, we use a
large propane torch which we call “the weed burner”. They are pretty
inexpensive from Harbor Freight (about $25, item #91033). For
another $15, you can buy one with a push button igniter. They can be
screwed into a BBQ propane tank. Be careful with the lever (full
blast option).
That's what I would do if I only had a torch available, I would
prefer using a forge. You could build a temporary one by stacking
firebricks in an oven shape and using a tiger torch for your heat
source. Either way hope it works out for you, let me know how it
goes.
Forges are very useful tools, a temporary forge would be fine for
this operation.
I wouldn’t heat copper of bronze in a permanent gas forge that I use
for ferrous metals.
I like to keep my ferrous and non-ferrous metals separate.
You neglected to describe the torch, what kind how big the tip is and
such. Many torches generate sufficient BTU and flame temp to anneal a
large copper sheet, but the copper conducts the energy so readily
that it acts like a giant heatsink radiateing energy acrosss its
entire surface faster than you can get it in. So it never gets above
a certain point.
In situations like this you need a barrier that slows the tranfer of
energy so it backs up in the copper i.e. insulation. This can be as
simple as stacking soft fire bricks around the sheet to form an
enclosure like a “forge”. Then heat the chamber you have created
with the torch. When all I had was a small torch I found I could
anneal much greate volumes then I could with the metal simply sitting
on a fire brick. I have several furnaces and torches now, but it
never hurts to have a box full of soft fire bricks. They are very
handy…
P.S. Normally I'd just make a torch. Really? Do tell us more,
sounds interesting.
If you or anyone else is interested, a good place to start is “Gas
Burners for Forges, Furnaces and Kilns” by Porter. He’s a decent
fellow that frequents a home casting Yahoo! list.
I bought the book as a starting point, if concentrates on the
venturi effect, and it is my aim to construct a small jewellers torch
that “only” requires propane to run, no oxygen.
I have diverged from the book and made my own designs that are
fairly cheap to make, and efficient to run.
Also look here for many burner designs from primitive resources
like off the shelf iron pipe fittings.
http://ronreil.abana.org/design1.shtml
May be primitive, but they do work well.
You can go to the hardware store and buy about $9 worth of plumbing
parts and you end up with a very efficient and powerful burner, that
uses only propane, and atmospheric air.
You need to get the gas accelerator just right and alignment is
important, as is the ratio of burner tube diameter to burner length.
Of that I am well aware. Thats why I mentioned the reference. I have
built burners for all kind of projects. Not everyones cup of tea, but
easy enough for those inclined to do it.
about when to tell when a piece of metal was annealed, the flame
I have one of those, doesn’t work well for the weeds here,