Materials:
- 15% solution of sulfuric acid
- 12 Volt car battery charger or equivalent
- Large beaker or suitable acid resistant container
- Container that can hold the acid beaker and cooling water
- Aluminum or lead cathode (negative) terminal for anodizing bath
- Wire to connect the anodizing bath to the power supply
- Ice
Procedure:
First the aluminum plate must be carefully cleaned so the reaction will
be even across its surface. I'll let you figure this part out.
Then, the aluminum plate to be anodized is connected to the positive terminal of
the power supply, and the cathode is connected to the negative terminal
as follows. It is important to keep in mind that copper wire or aligator clips
cannot be used in the acid bath since they will dissolve. An easy solution
to the problem is to make an oversized aluminum plate or at least leave a strip
on it that extends above the acid bath.
(Negative <-------------# A----------------> (Positive Power supply
Power Supply | # A | Terminal)
Terminal) | # A |
| | # acid A | |
| | # bath A | |
| | # A | |
| |----------------| |
| |
| Water Cooling |
| Bath |
|---------------------|
(The # signs represent the cathode and the A's the aluminum plate)
As shown the plates are place into the acid in the beaker and the beaker is in turn
placed in the tempered water bath. The water bath is used to keep the temperature
of the acid bath close to 20 degrees Celsius. Since a fair amount of heat is
generated by the process, simply add ice to the water bath as needed to maintain
a reasonably constant temperature. Now turn on the power, and start timing. The
bath should bubble a bit so be careful of spattering acid and fumes. After about
30 minutes has elapsed turn off the power, remove the plate from the bath, and wash
it well in cool water.
At this point the plate is usually immersed in an organic dye, and then boiled in
water to seal the pores and trap the dye in the oxide layer. This might be a good
thing to try first. Simply add food coloring, ink, or Rhitt dye to a beaker of
boiling water and dump the plate in this for about 10 minutes. If this worked
correctly you should get a dyed aluminum plate.
I think that if the plate were coated with a sensitizing solution rather than a dye,
and not boiled to seal it, it could be sensitized, exposed, and developed. I however,
have not tried this so can't tell you how best to make this work.
If you tinker with this let me know how it goes. If you have any questions let me
know, I'll let you know if I have an answer.
- Wayde Allen