Re: [ATM] Painting Titanium

[Anthony Stillman <atmer@flash.net>]

>Would be nice but obviously we aren't going to be anodizing.


Obviously?

Anodizing Titanium is easy.  All you need is a 3 to 110 volt DC power
supply (I usually work in the 30 to 60 volt range), some salt water (I use
ammonium sulphate) and a brush with a plastic handle and a metal ferrule
retaining the bristles.  By varying the voltage and/or repeatedly going
over the same section a wide variety of colors can be had.  If you try to
do the whole tube in one bath you'll need a good deal of current (10 amps
per square foot).  A brush worth at a time can be done with D cells.

The following table is excerpt from "Jewelry Concepts and Technology" by
Oppi Untracht.

Color            Voltage     Film Thickness in microns
Pale Yellow       3-5             0.0300
Straw Gold         10             0.0350
Dark Brown Gold    15             0.0400
Purple             20             0.0460
Blue Purple        25             0.0527
Deep Blue          30             0.0600
Medium Blue        35             0.0630
Pale Blue          40             0.0658
Blue Green         45             0.0700
Green Blue         50             0.0825
Pale Green         55             0.0950
Green Gold         60             0.1075
Rose Gold          70             0.1300
Red Purple         75             0.1400
Purple Gold        80             0.1500
Dull Purple        85             0.1600



A thick coating is more resilient than a thin one, but I find that
thickness over 0.1um produce colors that are too muddy for my tastes.

Also, there's no need for the DC supply to be well filtered.  Unfiltered
rectified AC will work.  My "painting" unit uses a variac to feed a full
wave rectifier and subsequently 2000 uF of capacitance.  There's a meg of
resistance across the cap to bleed off residual charge when the power is
off.  Exactly why that's there I'll be keeping to myself.

Anthony


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