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Bronze confusion


#1

I’m hoping that you all will be able to help me straighten out my
confusion over bronze. This months Jewelry Artist has an article
about bronze which brought the subject to mind. Some time ago I
asked my instructor to clarify what was bronze and what wasn’t
bronze. She said that all sorts of alloys are called bronze and can
indeed be considered bronze but she expressed some doubt and
confusion as well.

So here are some of my questions.

  1. Metalliferous and Rio sell Jewelers Bronze which is 85% copper
    and 15% zinc. Traditional bronze is an alloy of copper and tin. The
    Jewelry Artist magazine says beware of Jewelers Bronze. Why?

  2. Does the color of Jewelers Bronze differ significantly from a
    copper and tin alloy?

  3. If I sell a piece of jewelry made with the Jewelers Bronze alloy
    and call it bronze will I be duping the customer?

  4. Patina. If I follow patina instructions for some of the more
    exotic bronze patinas do I have a chance that the Jewelers Bronze
    will patina in a similar manner?

  5. My instructor used Red Bronze when she was in school. What is
    that?

  6. The Jewelry Artist article refers to NuGold available from
    OttoFrie as a bronze. Their site, as near as I can see, doesn’t say
    what the alloy is.

  7. There was a lot of discussion about bronze turning pink in pickle
    in the Jewelry Artist article. I have seen brass and Jewelers Bronze
    turn pink. I thought it was from the heat of the torch bringing up
    the copper. Now I’m confused. Is it the pickle that is actually
    doing it or is it a heat induced oxide that reacts with the pickle
    to show up pink?

  8. In some of the pieces I’ve made I liked the pink so much I left
    it on there and waxed over it, but this last one I used super pickle
    to get rid of the pink. The piece turned a really weird bright
    yellow. What is the best method for knocking this off and getting
    back to the original metal color? I sort of rubbed away for a bit
    and then threw it into Live of Sulphur. It was OK, but not as good
    as I think it could be.

  9. Then there was the mention of “metal fever” that could be induced
    by zinc fumes. Wear a respirator or suffer the consequences…
    yikes! In an article by Charles Lewton Brain on metal safety he
    mentions the same fever thing with copper. Do I actually need to
    wear a respirator with occasional soldering on either copper or
    brass or bronze?

Deborah Donaghue


#2
What is the best way of getting the pink off bronze "(after
pickling) 

we would dip the metal into a solution of 50% pickle and 50% peroxide
after it came out of the pickle. After it sat there awhile, the pink
would be gone… Dee


#3
I'm hoping that you all will be able to help me straighten out my
confusion over bronze. This months Jewelry Artist has an article
about bronze which brought the subject to mind. Some time ago I
asked my instructor to clarify what was bronze and what wasn't
bronze. She said that all sorts of alloys are called bronze and
can indeed be considered bronze but she expressed some doubt and
confusion as well. 

It is a confusing topic there is lots of historical nomenclature
that doesn’t strictly follow naming rules. Here are the basic rules,
copper zinc alloys are called brasses except for commercial bronze
which some catalogs call jewelers bronze. Historical bronzes were
copper tin alloys but modern naming has added copper aluminum, copper
silicon and copper titanium alloys to the bronze family. There is so
much confusion about the names of the alloys that a system of numbers
with strictly defined alloy composition was developed. For
on standard designations and the reasoning behind them go
to

http://tinyurl.com/2nqgpr

They have an alloy number system that is used to identify copper
alloys:

Coppers (C10100 - C15999)
High Copper Alloys (C16000 - C19999)
Brasses (C20000 - C49999)
Bronzes (C50000 - C69999)
Copper Nickels (C70000 - C73499)
Nickel Silvers (C73500 - C79999)

If you want to get an idea of how many copper alloys there are and
their properties go look up the properties of wrought copper alloys.

http://tinyurl.com/l2n3tu

or download a PDF file with the alloy numbers, names and chemical
composition at

1. Metalliferous and Rio sell Jewelers Bronze which is 85% copper
and 15% zinc. Traditional bronze is an alloy of copper and tin.
The Jewelry Artist magazine says beware of Jewelers Bronze. Why? 

No good reason, it is a wonderful alloy to work with, but it is 87%
copper 13% zinc, “Red Brass” is the name of the 85% Copper 15% Zinc
alloy. This is a prime example of the problem. If you really want to
know what you are getting you must use the alloy number not the
Trade Name. I just read the article and found it is really lacking in
detailed on which alloys are being used and makes
blanket statements like "Brass melts at "1750 F and bronze at 1866 F"
Which alloys? there are literally hundreds each with different
melting points and other properties. in this case the author is
probably referring to “cartridge brass” (C26000) which is the most
common brass we run into as metalsmiths and I could not find a bronze
with a melting point of 1866 but as I said there are hundreds of
alloys. But if you were to use the in the article and had
a piece of “Jewelers Bronze” which is a brass and tried the melt test
it would melt at 1895 F, very close to the temperature the author
lists for tin bronze.

The Bronze alloys that you will be most interested in as a
metalsmith will be the “A” phosphor bronzes. They are available in
sheet and wire form and are likely what the article was trying to
refer to.

C51000 Phosphor Bronze, 5% tin
C52100 Phosphor Bronze, 8% tin

C51000 is available from mcmaster.com in wire and sheet form in
small quanities they call it alloy 510 which is an older numbering
system.

 Does the color of Jewelers Bronze differ significantly from a
copper and tin alloy? 

Which alloy?

If I sell a piece of jewelry made with the Jewelers Bronze
alloy and call it bronze will I be duping the customer? 

Nope, it is the accepted trade name.

Patina. If I follow patina instructions for some of the more exotic
bronze patinas do I have a chance that the Jewelers Bronze will
patina in a similar manner? 

Get a copy of “The Coloring, Bronzing and Patination of Copper
Alloys” and you will see this is a difficult question to answer. But
basically it could be close but could also be way off, it will depend
on the recipe.

http://www.ganoksin.com/jewelry-books/us/product/0823007626.htm

My instructor used Red Bronze when she was in school. What is that? 

Probably it was Red Brass as there are not any standard trade names
that include red and bronze.

The Jewelry Artist article refers to NuGold available from OttoFrie
as a bronze. Their site, as near as I can see, doesn't say what the
alloy is. 

It is not bronze. From the Otto Frei website: “Nugold is a brass
alloy with a color that slightly resembles gold” my guess is that it
is either Red Brass, Commercial Bronze or possibly Jewelers Bronze

There was a lot of discussion about bronze turning pink in pickle in
the Jewelry Artist article. I have seen brass and Jewelers Bronze
turn pink. I thought it was from the heat of the torch bringing up
> the copper. Now I'm confused. Is it the pickle that is actually
doing it or is it a heat induced oxide that reacts with the pickle
to show up pink? 

It is the alloying elements being oxidized away by the heat and then
being dissolved by the pickle, the resulting surface is now copper
rich. It is the same process as depletion gilding.

 In some of the pieces I've made I liked the pink so much I left it
on there and waxed over it, but this last one I used super pickle to
get rid of the pink. The piece turned a really weird bright yellow.
What is the best method for knocking this off and getting back to
the original metal color? I sort of rubbed away for a bit and then
threw it into Live of Sulphur. It was OK, but not as good as I
think it could be. 

The hydrogen peroxide pickle actually dissolves the copper leaving
an alloy rich surface that is why it looks like yellow brass now.
Mechanical abrasion is the best bet to fix it at this point. A very
quick trip in and out of the H2O2 pickle will do less damage to the
surface but it is difficult to control.

Then there was the mention of "metal fever" that could be induced by
zinc fumes. Wear a respirator or suffer the consequences.... yikes!
In an article by Charles Lewton Brain on metal safety he mentions
the same fever thing with copper. Do I actually need to wear a
respirator with occasional soldering on either copper or brass or
bronze? 

All metal fumes are bad news, zinc fumes can be serious if you get
enough of them even fatal if you had serious medical problems
already. Ventilation is the key safety practice here, do not solder
or cast without proper ventilation, just don’t do it.

FWIW all the common bronze alloys that these folks are using contain
a small amount of zinc as an alloying element also lead and iron.
Look it up in the copper.org data. Virtually all bronze and brass
alloys contain small amounts of lead and iron. These elements are
typically there as contaminants that cannot be economically removed
but in the machining alloys, the so called free cutting brasses and
bronzes there can be several % (1-4%) of lead in the metal. You
cannot tell these alloys from the others without chemical analysis so
using scrap metal can be quite dangerous to your health as heating
leaded alloys will give off significant amounts of lead fumes.

Invest a little time at the copper.org site and try to order copper
alloys by alloy number not trade name so you are certain of what you
are working with.

James Binnion
James Binnion Metal Arts


#4

Traditional bronze is indeed copper and tin. But in general, that
alloy is more suited to casting than to fabrication. It tends to be
harder, and a bit brittle, depending on the exact alloy. Historical
bronzes also often had a bit of lead, which increased that hardness
and brittleness, but also made it a bit easier to melt and cast.

I’ve no idea why your magazine doesn’t like “jewelers bronze”, which
of course is also an inexact description. Most of the so-called
bronze alloys sold to jewelers in sheet or wire form are technically
brass, but lower in zinc than standard brass, hence a redder color.
If you are looking for a more traditional “bronze” color, then some
of the lighter colored brass/bronze alloys you might get could be too
light. Nu-gold is an example. It’s designed to mimic, sort of, the
color of 14K yellow gold. Some refer to it under the same bronze
umbrella, but it’s really closer to a standard brass.

Does the color of Jewelers Bronze differ significantly from a
copper and tin alloy? 

The color depends on the amount of alloy added to the copper. That’s
true for true bronze as well as the brass versions. The so-called
commercial red brass often sold as “bronze” to jewelers is pretty
close to tin based bronze in color, especially after it’s been
allowed to develop a bit of patina.

If I sell a piece of jewelry made with the Jewelers Bronze alloy
and call it bronze will I be duping the customer? 

No. This isn’t a distinction anyone really would care about, having
no effect on the value or utility of the work. The trade calls these
red brass alloys a bronze simply in reference to the redder color.
You shouldn’t worry too much about using the names the same way. if
you wish to explain further to your customers, they may well be
interested in the details, but I doubt the lack of that explanation
would matter to anyone.

Patina. If I follow patina instructions for some of the more exotic
bronze patinas do I have a chance that the Jewelers Bronze will
patina in a similar manner? 

Similar. Maybe not exact, or at the same speed, but most of the
patinas will work about the same. Remember that different versions of
the red brasses will patina differently, but a little bit perhaps, as
will different formulations of a true bronze.

My instructor used Red Bronze when she was in school. What is that? 

As noted above, commercial red bronze is a red brass, not a true
bronze. The name refers more to the color as compared with the usual
color associated with brass. You can get casting metal in a true
bronze, but not normally sheet metal, since it simply doesn’t work
very well compared to the brass alloys.

The Jewelry Artist article refers to NuGold available from OttoFrie
as a bronze. Their site, as near as I can see, doesn't say what the
alloy is. 

It too, is a brass. Not sure if it’s just copper and zinc. I seem to
recall a bit of silver, or perhaps something else, added as well. But
the main alloy is copper and zinc, so far as I know.

There was a lot of discussion about bronze turning pink in pickle
in the Jewelry Artist article. I have seen brass and Jewelers
Bronze turn pink. I thought it was from the heat of the torch
bringing up the copper. Now I'm confused. Is it the pickle that is
actually doing it or is it a heat induced oxide that reacts with
the pickle to show up pink? 

This is a common confusion. Just as people talk about “bringing up
the fine silver” when annealing and pickling sterling silver. It
doesn’t actually bring up copper with brass or bronze, nor does it
bring up fine silver. But the same thing is actually happening. In
both cases, the more reactive metal, zinc or tin in the case of brass
or bronze, or copper in the case of sterling silver, is oxidizing,
and to a greater degree than the main metal. When you pickle it, you
remove the oxides. In the case of sterling silver, you’ve depleted
the surface of the copper when you pickled off the copper oxide. In
the case of both brass and bronze, you deplete the surface of the
zinc or tin, leaving a surface of mostly copper. Unlike with silver,
this copper will also have oxidized. The outer layer of black copper
oxide will pickle off. An inner boundary of red copper oxide won’t
completely pickle off (unless you go to a more active agent, like
adding peroxide, or your super pickle). This trace of red copper
oxide imbedded in the surface rather than on top of it, combined with
the now no longer polished/bright surface of the metal, is the source
of the much of the pink color. If your pickle isn’t new, and already
has a fair amount of copper oxides dissolved, then you can get more
pink, when the zinc or tin oxides dissolve into the pickle, and cause
an electrolytic reaction that electroplates back a thin film of
copper. That surface, being even more porous and “matte”, just as it
does with silver pickled in contact with iron, is even more pink.
There’s little difference between brass and a true bronze in the
colors you get this way. The brass, since zinc is more reactive than
tin, will do it faster.

In some of the pieces I've made I liked the pink so much I left it
on there and waxed over it, but this last one I used super pickle
to get rid of the pink. The piece turned a really weird bright
yellow. What is the best method for knocking this off and getting
back to the original metal color? I sort of rubbed away for a bit
and then threw it into Live of Sulphur. It was OK, but not as good
as I think it could be. 

Your choice of abrasive will remove any surface coloration and get
you back to the actual color of the metal. Pumice is a good one, or
just about any other decently abrasive material.

Then there was the mention of "metal fever" that could be induced
by zinc fumes. Wear a respirator or suffer the consequences....
yikes! In an article by Charles Lewton Brain on metal safety he
mentions the same fever thing with copper. Do I actually need to
wear a respirator with occasional soldering on either copper or
brass or bronze? 

It’s probably not essential, but no matter what the metal, it’s
always a good idea to at the least have good ventillation. Metal fume
fever requires the zinc (or worse, cadmium) to actually vaporize, and
little of that happens when you just solder the metal, since it’s not
really hot enough. Melting the metal, especially if you overheat it,
is a different story. but no matter what, you’ve also got fumes from
soldering fluxes and the torch itself. Good ventillation is key.
Especially since most less expensive things like a mask aren’t
designed to remove these things, and the sort of cartridge based
respirator that actually can remove such fumes are uncomfortable, and
a bit pricey. Still, it’s good to have one around. Soldering and
melting aren’t the only operations where really good respiratory
protection is a good idea.

Peter


#5
Then there was the mention of "metal fever" that could be induced
by zinc fumes. 

Deborah, I’m sure some others know more about most of your questions
than Ido. I don’t think you would really be “duping” your customers
about names, because the value is about the same in any case - if
you gold plate silver and sell it as gold, that would be duping your
customers, IMO.

Metal fume fever is very real, but in order to get it you need metal
fumes - in this case metal dust could be considered fumes. It’s not
a problem with simple handling or even soldering it normally. It’s
when you melt it, weld it or inhale polishing dust that gets you.

Here: http://en.wikipedia.org/wiki/Metal_fume_fever


#6

Hi all, the bottom line is copper and tin is bronze and copper and
zinc is brass. Calling red brass jeweler’s bronze is a deceptive
marketing plow or comes from plain ignorance.

That’s it. Vince LaRochelle.


#7

I can’t answer any of your questions about bronze. However I do want
to repeat Charles Lewton Brain’s admonition about working with copper
and bronze. Copper fume poisoning is very serious.

A friend, who works with large pieces of copper in her sculptures,
developed copper fume poisoning. Fortunately it was a mild case, but
enough to demonstrate to her the advisability of wearing a
respirator.

There are so many neurological diseases caused by toxins, and
noxious fumes that one needs to take heed of the warnings.

Alma Rands


#8
we would dip the metal into a solution of 50% pickle and 50%
peroxide after it came out of the pickle. After it sat there
awhile, the pink would be gone.. 

You don’t need that strong a mix. Eight ounces of 3% hydrogen
peroxide to 1 oz pickle is a reasonable ratio. It just needs enough
acid to activate the reaction.

James Binnion
James Binnion Metal Arts


#9
the bottom line is copper and tin is bronze and copper and zinc is
brass. Calling red brass jeweler's bronze is a deceptive marketing
plow or comes from plain ignorance. 

Unfortunately it is not that cut and dried. Many alloys that are
called bronze are really brass by technical definition. In other
words the largest alloy component is zinc. Examples like jewelers
bronze, commercial bronze and manganese bronze all are in the brass
category but have been called bronzes for many, many years probably
dating back to their invention. These definitions of what
constitutes a bronze or brass are probably more recent than the
majority of the alloys themselves.

James Binnion
James Binnion Metal Arts


#10

I think I can shed some light on the subject of art bronze ( bronze
used for sculpture )

Composition: copper and tin. Nothing else should be added. Why some
recipes mention lead and other metals ? To cut cost. Tin is
expensive.

Casting: one should never buy bronze for casting. It is when you re-
melt bronze, the issue of fumes becomes a problem.

Cast bronze by melting copper alone. When liquid, crucible is taken
out of furnace and tin is added. Skim, stir, and pour. Adding tin
effectively brings melting point down and insures that metal stays
liquid longer.

Copper toxicity: Depends on a person. My entry in the world of metal
working happened in the bronze foundry. We poured 2000 lbs at a time.
Big time exposure and no ill effect, but we never re-melted sprues,
buttons, and etc.

However, if persons diet has a lot of onions and garlic, the sweat
can become very acidic. Copper and acetic (vinegar) acid does form
toxic compound to which some people could have severe reaction.

The necklace of Marie Antoinette disappeared during French
Revolution, but was found many years later. It was in a copper box.
One latch was broken, so it was sent out for repairs. The jeweler,
who
worked on it, scratched his hand on the corner of the box, and later
died from it.

Leonid Surpin
www.studioarete.com


#11

Deborah, names for copper alloys are confusing. The Rio catalog says
that its brass sheet is “CDA #230 alloy (85% copper/15% zinc). Also
known as Jeweler’s Bronze or Merlin’s Gold…” The Indian Jewelers
Supply catalog calls this same alloy (#230) red brass, and adds that
it is also known as Craft Gold, and Rich Low Brass. In other catalogs
you will find this (the #230 alloy) called NuGold. Check with
Metalliferous – an old catalog which I have says that they carry
"Commercial Bronze," which is CDA #220, and is 90% copper and 10%
zinc (i.e., a lower-zinc version of brass). And so on!

Yes, technically, bronze is an alloy of copper and tin (the most
ancient Mesopotamian bronzes were arsenic-bronzes, i.e., arsenic
rather than tin was the alloying agent in the copper; brass did not
really exist until Roman times).

As to color, in my experience, brass usually looks like gold, and
bronze (copper/tin) has a much browner look to it, although that can
vary.

If an article says to beware of Jeweler’s Bronze (brass), it was
probably written by a person who has little experience with it. I
work almost entirely in brass and love it (as I have noted over the
years in this forum) for reasons which I won’t repeat here.

My advice is that if you make an item from “Jeweler’s Bronze,” you
should note to your customer that it is technically brass. In my
opinion, the word “brass” (in English) can have negative overtones
(e.g., inappropriately yellow hair, usually dyed, is called
"brassy"; a person who is loud and pushy may be said to have a lot of
brass). The word “bronze,” by contrast, is more positive – a
desirable skin color (for white folks) is said to be bronze. The word
has more of an aura of wealth (great sculptures, etc.) to it. I think
this is why some people (verbally) like to make a brass into a
bronze. Personally, I use the word “brass” without apology.

As to “red bronze,” I assume it was also a brass. As for patinas,
just try whatever you want. You may be pleasantly surprised.

Brass,when annealed and soldered at high temperatures, will always
turn pink/red and also black. The black (which comes off easily in
PhDown, i.e., sodium bisulfate) is cupric oxide, and the red is
cuprous oxide. This comes off in bright-dipping (I use dilute nitric
acid for this; a pickle solution with hydrogen peroxide added is a
slower but less noxious way of bright-dipping). Again, check the
Orchid Archives for more discussion on this. After bright-dipping,
the metal will be a lovely matte gold color. Your use of the pink
color as an integral part of your jewelry piece is a great idea,
because it won’t wear off. I don’t think it needs waxing.

As for using a respirator, it’s always a good idea, under any
circumstances. I must admit that I do not always use one because I do
not work full-time at this (although I always used a respirator when
I was using solders alloyed with cadmium).

Hope this helps.

Judy Bjorkman
Owego, NY USA


#12

To add to Leonid’s reference to the jeweler who died when he
scratched his hand on the Marie Antoinette’s copper box, I heard
that several years ago an enamelist who was working with some copper,
got a sliver in her hand. It became badly swollen and extremely
painful, infected, and she needed emergency treatment for it.

I was unaware that when bronze is remelted the fumes become a
problem… Think I will stick to silver for casting and exercise full
precautions.

Alma Rands


#13
I was unaware that when bronze is remelted the fumes become a
problem.. Think I will stick to silver for casting and exercise
full precautions. 

The problem arises because temperature of melt is much higher than
melting temperature of tin. And if lead is involve, it is even
worse.

Leonid Surpin
www.studioarete.com


#14

Along these lines, has anyone used Rio’s “Ancient Bronze” for
casting? I have cast many belt buckles and small sculptures with
NuGold and would like to try the Ancient Bronze. Is its behavior
during melting and pouring about the same as NuGold? Any fume issues?
As always, whatever experiences you could share would be most
helpful.

Many thanks,

Jessee Smith
Cincinnati, OH
www.silverspotstudio.com


#15
Along these lines, has anyone used Rio's "Ancient Bronze" for
casting? I have cast many belt buckles and small sculptures with
NuGold and would like to try the Ancient Bronze. Is its behavior
during melting and pouring about the same as NuGold? Any fume
issues?

use some: cda 873

http://www.atlasmetal.com/silicon-bronze-everdur.php

available in polished shot -will melt in an electro melt or with a
torch. this is what most US scupture is cast from.

don’t believe Russian old wives tales!!!

jesse


#16

I was unaware that when bronze is remelted the fumes become a
problem… Think I will stick to silver for casting and exercise
full precautions.

The problem arises because temperature of melt is much higher than
melting temperature of tin. And if lead is involve, it is even
worse. 

It would seem that if excessive temperatures were to be avoided, that
the technique you recommended earlier - melting pure copper and then
adding tin - would not be advisable. Pure copper melts at a much
higher temperature than any bronze: 1084 Celsius or 1983F according
to this handy chart:

http://www.engineeringtoolbox.com/melting-temperature-metals-
d_860.html

The melting temperature of tin, of course, is much lower: 232C or
449F; but that doesn’t have much relevance to the temperature range
at which bronze is cast. The eutectic - the melting point of the
alloy - is what’s important. The addition of tin to lower the
melting point of copper is what allowed the Bronze Age to flourish;
the temperatures required to melt pure copper were not practically
attainable at the time. It’s common practice in the foundry trade to
remelt up to 50% by weight of clean gates and risers; it’s not
associated with any increase in fumes, at least among art foundries
using modern alloys (which, in the US anyway, are mostly silicon
bronzes.) Even if you’re casting brass, which has a lot of zinc in
it and a corresponding tendency to fume, pre-melted metal will tend
to contain less zinc, since some will have fumed off the first time
it was melted.

Andrew Werby
www.unitedartworks.com


#17

Hi Jessee:

I’ve used it for years. Great stuff. I’ve never tried to cast NuGold,
so I can’t say how they relate, but the ‘ancient’ bronze is a bit
thicker than herculoy. Flows just fine in a centrifuge caster. I’d
describe the viscosity as about ‘maple-syrup-like’. (Good maple
syrup, not the Aunt Jemima grade stuff.)

I’ve been casting it at school for about 10 years with no problems,
and no visible fuming. Great stuff. Can be forged and manipulated
after casting if you’re very careful.

FWIW,
Brian Meek.


#18

Thank you all for your thoughts and time. I’ve come away
from this discussion with some wonderful nuggets. Get myself better
ventilation

Enjoy Jewelers Bronze
Be Thankful for all the good folks out there

Deb
Deborah Donaghue


#19

Ancient Bronze makes a nice product, but it is weird to melt. The
melt temp is high, and the metal stays dry looking and scummy on top
when it is actually all hot and ready to cast. You’d better have a
big torch.

M’lou


#20

Jesse, I recently cast 25 articles with the Ancient Broze and they
came out perfectly. The articles were a small machine part for
faceting machines. Very accurate, durable and easy to cast (though I
did use two torches to get the temp needed). I ran the flasks up to
1350 to insure complete fill. Didn’t loose one piece. I did it
centrifugal in a large open room with fans and couldn’t detect any
fumes problems. I have also cast NuGold in the past and would say
they are very similar though NuGold didn’t need quite so much heat I
would say.

Good luck. Don in SOFL.