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Preserving patina on copper


#1
On copper or brass, verdigris-type patinas-- if you let the patina
grow slowly over time by enclosing the piece with (not in) a dish
of ammonia, etc, the patina will be so durable that you can buff
over it without damage. Patinas that happen quickly seem to come
off the same way. It may take a day or two with the more passive
method, but the results are worth it. 

You may want to limit the patinating(!) situation to a day or two. I
let mine sit for longer (can’t remember how long) and got a
beautiful patina, but it turned all of the metal to “patina,” and of
course the earrings were brittle and useless.

Judy Bjorkman


#2

There are differences between cold and hot patination. Claire
Sanford who wrote a chapter on patination in Tim McCreight’s book,
“Metal Technics”, was my instructor at Mass Art. The ammonia style is
a “cold” technique, where you insert your copper or bronze piece in a
bag, lightly mist it with water and sprinkle a light coating of salt.
Place the piece in a bag with a dish of ammonia and let the piece
"cook" for 24 - 48 hours.

The other process that Noel described is commonly called a "sawdust"
patina. This can be done with other items than sawdust, such as
macaroni of all things. Different woods have different oils and
acids, such as oak, cedar, pine, maple, etc. Each one will react
differently to the patina mixture. You can get some pretty amazing
colors with the ammonia and certain sulfates, like copper sulfate.
Don’t saturate the wood chips, just make sure they are moist and make
very sure that your wood chips are not from pressurized wood or some
wood that has critter reducing chemicals. When you open the bag, be
sure you are outside or wearing a respirator or both. Man, it is
really whiffy!

The second process is using heat. By using a torch, you gently heat
the piece using a light spray with either cupric nitrate, ferric
nitrate or cupric sulfate and alternate between heating and spraying.
This builds up a coating of patina onto the copper. Too much heat and
you will burn the patina. Too little heat and the patina won’t stick.
In either case, the copper needs to be completely grease free.

For cold patination I like Butcher’s wax. It is intended for cold
work. Apply a light coating, let it dry completely and buff with a
soft cloth. I like to do this about three times.

Renaissance Wax is best for hot metal patinas and should be warmed
slightly to allow the wax to grab onto the pores of the patination
right down to the metal. This also needs two applications and should
be allowed to dry for at least two hours before buffing.

I’ve used both and the pieces still look as nice as the day I made
them.

You might take a look at Japanese Patina

http://www.ganoksin.com/jewelry-books/us/product/1929565119.htm

-k

M E T A L W E R X
School for Jewelry and the Metalarts
50 Guinan St.
Waltham, MA 02451
781 891 3854
www.metalwerx.com


#3

Cool - I didn’t know about the sawdust technique using different
woods. My father-in-law is an excellent woodworker (when he feels
like it) but if I mention it to him I’ll bet he’ll bring me 10
different kinds of sawdust for Thanksgiving.

Brian Corll
Brian Corll, Inc.
1002 East Simpson Street
Mechanicsburg, PA 17055