Subject: colored finishes on titan

From: [email-masked] (Douglas Wiggins)
Date: Sun, 19 Feb 1995 00:27:00 GMT

MS-I'm looking for info for a friend on how to produce the
MS-pretty colors on titanium metal - such as seen on
MS-earings. Thanks.

MS-Mark Williams [email-masked]

Titanium and niobium are "reactive metals". When oxidized, a layer
is formed which interferes with the reflection of light - when
light passes through the oxide and is reflected, it actually
interferes with its own reflection, resulting in a shift of the
light to some other portion of the spectrum, like when light
reflects off of an oil spill on water. This oxidation can be
done by simply heating the metal, but this is very difficult to do
with precision. Electrolytic oxidation is the preferred method -
just polish the metal (the shinier the surface, the better it will
reflect the light, so the brighter the color) and submerge it in
just about any fluid (CocaCola has been used, but a tiny pinch of
salt in solution would be very good), with one electrode hooked to
the metal and the other dipped into the solution (or connected to
the container, if it is metal); when electricity is applied (direct
current is the most safe), it will cause the anode (the positive
lead) to oxidize (if I am remembering correctly). The amount of
oxidization can be accurately controlled by the voltage provided.
For titanium, six colors, ranging from red to blue, can be obtained
(three bright colors and three pastel shades). Often, the piece is
withdrawn from the solution as the voltage is varied, to provide a
range of colors on the item. I use the DC motor speed controller
that I normally use to power my lathe. Titanium always has a layer
of oxide on it, although it may not be visible, so it never rusts.

Please note: this treatment is not durable; it is a surface effect,
and easily scratched. If used for wrist or belt ornaments, it will
quickly become ugly from wear.

Niobium produces brighter colors, but I don't know much about it. A
company named Reactive Metal Studios offers these and other jewelry
metals, including some which are layers of different metals
sandwiched together, then stressed or pock-marked, then sanded to
reveal the layers. For larger dimension stock-metal, I buy my
titanium from President Titanium (which I use for tools in
glassblowing, since it does not transmit heat - it is practically
an insulator: you can get titanium red-hot, and pick it up by the
fingers an inch or so away) - you can find all kinds of sources for
this valuable metal in the Thomas Register (in the US), found in
the library reference section (it is the shelf-full of large green
volumes) - oh, when I say "valuable": it is pretty spendy, but
when making jewelry only a small amount is used. One of the reasons
it may be spendy is that it must be smelted in an inert atmosphere
and it must be melted in a refractory that is made of radioactive
elements (our local manufacturer of titanium parts was hit by a
suit from the city to clean up the drain-way which had been
receiving the washings from their castings because of the
radioactive principles involved). If not worked in an inert
atmosphere, it will burn into titanium oxide, which is used to make
titanium-white paint, the whitest paint you can get - if used as
"flat", it is 97% reflective. If you intend to fabricate with it,
it requires an inert atmosphere to weld it, too.

I use titanium isopropoxide, an organic form, as a spray to put a
rainbow hue on glass (when sprayed on hot glass, the titanium metal
is released onto the surface). This effect is sometimes called
"iridescent", because the colors are reminiscent of that effect,
but the definition of iridescence is that it changes color upon the
angle of incident light, and the colors formed by titanium (and
other metals; for glass, tin and iron are more commonly used) does
not change - if a spot is blue, it is always blue, no matter from
which direction the light comes.

Did you find out what you wanted to know? Isn't the Internet great?

  -Douglas Wiggins [email-masked], Portland, Oregon
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 * OLX 2.1 TD * Zoron Research, Inc. - Custom Glassblowing to spec