Black ring

Jewelry Discussion
21

This website WebElements Periodic Table » Gold » the essentials claims that a black
gold alloy is possible with cobalt. They state:

"Remarkably, other colours such as purple (a gold:aluminium
alloy), blue (a gold:indium alloy) and *even black (a gold:cobalt
alloy) may be formed."

Wikipedia has an article on the chemical surface treatments for
blackening gold, along with a description of the femtosecond laser
surface treatment: Colored gold - Wikipedia

Mark Bingham
http://fourth-axis.com

22 
Purple gold has been known for a long time.

Don’t know anything about black gold except I’ll send the customer
onwards if they ask for it.

Somewhere I have a book of formulas from the mid 1800’s. Formulas
for everything you can imagine - cleaning products, colic cures. It
has formulas for blue gold, purple, red, everything. The reason
those have been known for so long but you don’t see them in the
marketplace is obvious: They don’t work in jewelry. Workability,
durability, longevity, all the things that are needed to put out
quality work just aren’t there.

23 
"Black gold" is not just an expression anymore. Scientists at the
University of Rochester have created a way to change the
properties of almost any metal to render it, literally,
black....:-)....!

It is still a surface treatment. It is just a modification of the
surface so it doesn’t reflect light, it is not making the bulk metal
black. So it is really no different than a plating or patina in that
it is only on the surface.

James Binnion
James Binnion Metal Arts

24 
"Remarkably, other colours such as purple (a gold:aluminium alloy),
blue (a gold:indium alloy) and *even black (a gold:cobalt alloy)
may be formed."

It is not black till oxidized, and it is still a surface treatment.
There was maybe still is a company selling that alloy a few years
ago. It is put in a kiln as part of final finishing to create the
black oxide. It wears off after a while. Purple and Blue golds are
intermetallics. Pretty but not very useful too brittle and prone to
corrosion that makes them look ugly.

James Binnion
James Binnion Metal Arts

25 
It is still a surface treatment. It is just a modification of the
surface so it doesn't reflect light, it is not making the bulk
metal black. So it is really no different than a plating or patina
in that it is only on the surface.

It would be a “true” black though, not a dark purple or dark blue.
It would be great for a solar application… CIA

26

Continue from

I am not sure if this is still a topic to be solved, or not, but the
easiest way to provide a durable black ring is to make it out of
Niobium. You can get that from Reactive Metals. I works easily grey
(including setting). The last thing you do is to heat it to create a
durable dark charcoal to black oxide, or anodize it black. Read these
articles to find out moRe:

Working With Niobium - Ganoksin Jewelry Making Community and
http://www.ganoksin.com/gnkurl/1yo

Peter Deckers
from New Zealand

27 
I am not sure if this is still a topic to be solved, or not, but
the easiest way to provide a durable black ring is to make it out
of Niobium.

Yes it will be black but niobium oxide is not all that hard, it will
wear off fairly quickly. Titanium, niobium and zirconium will all
form a black oxide when heated enough in air or other oxidizing
environments but only zirconium and a special alloy of titanium have
a reasonably durable oxide layer for use as a ring.

James Binnion
James Binnion Metal Arts

28

The main problem with coloring metals like Titanium, niobium and
zirconium is surface preparation, and control of heat. They need to
first be cleaned, but not just clean but CLEAN, I usually steam
clean the piece, then sonicate it for about 10 minutes. Then I
passivate the ring, to remove any lingering ferrous materials. Then a
light etching is in order.

Then the next problem is heating the metal. this needs to be done in
a way that is extremely uniform across the surface of the piece, and
variation of 5 degrees is unacceptable. this will result in slightly
different oxide colors. So if you want true black, and an even
black, even temperature is crucial. I probably did a dozen different
things, from a dental kiln to a homemade furnace, just to finally
find a way to control the heat, and get it nice and even.

here is a photo of a black titanium ring I recently made, next to a
plain titanium ring.

http://www.ganoksin.com/gnkurl/1zg

I think it’s a great effect personally.

-Chris

29 
Then the next problem is heating the metal. this needs to be done
in a way that is extremely uniform across the surface of the piece,
and variation of 5 degrees is unacceptable.

The best way to get this uniformity is a molten salt bath.
Temperature uniformity, speed of heating, control of oxygen level
are all more easily achieved in a salt bath.

James Binnion
James Binnion Metal Arts

30

Stunning rings Chris! How do you work with these metals - ie. forge,
file, shape etc.

Cyndy Wolf

31

Chris,

I like the black look! But they are both beauties!

john

32

What about tungsten… I have blackened it by heating it almost white
and threw it in oil to cool (a tungsten ring) and love the effect! I
even repeated the proces just to see how far I could go… It looks
like it’s very durable!!

All the best,
Stephen