Was: Best metalsmithing book
Marlin: this sounds great - do you just "paint" on the peanut oil in a thin coat and then torch it? Does it "flame" up like boric acid/borax/alcohol mix? Or does it just "melt" into the copper and harden? Is there some way to tell when you have "torched" it enough? Or is it a matter of the color you are seeking? I'm anxious to try this. Also....does it come off if put in pickle? I'm thinking of using it with some marriage of metals I have but if I flame it with the torch, then the silver/nickel portions of the piece also turn or can you paint the silver portions with boric acid mix and the copper with peanut oil and then torch it? And lastly how "permanent" is it? If it turns to "varnish" as you say, then it seems it would be fairly permanent. How do you remove it if you don't like it? Anxious to hear as I want to try it this week.
I had another offline inquiry into the use of peanut oil to patina
copper. To clarify the little that I know I submit the following In
searching the Orchid archives, I found this 10 year old post
which is basically the same as what I do on a much larger scale. I
use a bushy yellow reducing flame. I just tried a small butane/air
torch without much air and it worked much better than my Oxy/pr=opane
or acetylene torches. The way I do it is to wipe a thin film onwith a
cotton q-tip dampened with a bit of oil, heat until it barely smokes
pull it from the flame and q-tip it again - sometimes I will q-tip
one side while heating the other side - generally catching the q-tip
on fire. It behaves as you would expect an over heated oil in a
skillet to behave. Keep doing this until you get the finish you need.
Other oils may work better - walnut, flax (linseed), canola or
perhaps some oil fine art painters use. You can also see some neat
iridescent type colors similar to western raku fired pottery. These
colors may be impermanent, I do not know.
It is difficult to precisely control, and I doubt that you would be
happy with a mixed metal piece, it would likely dull the silver way
too much. I have never tested the durability, but assume it
approaches the durability of varnish. I would also compare it to the
process of curing a cast iron skillet in the oven, and would guess
that if you have a casting oven or even a high temp toaster oven you
could get more controllable and repeatable results.
As for removing this finish, a hot enough oxidizing flame followed by
pickle would work, I bet a paint stripper would also do a reasonable
job. Remember though, that you have heated and oxidized the
underlying metal as well, so when you remove the finish, the metal
will most like have a oxide coating unless you pickle it.
An interesting note about copper and oil. When I anneal copper, I
will sometimes cool it in oil. When the red hot copper hits the oil,
it acts like a reducing agent and partially cleans the nasty black
oxides from the copper, sometimes leaving the nice deep red oxides
behind.
Again, I urge you to read Peter’s 1999 article as well. I am no
expert on this technique, just a fan of playing with fire and metal.
Marlin