On Sat, 16 Jul 2005 16:40:27 GMT, "RadioGuy"
wrote:

[snip]

Good to know. You might find that a dip in vinegar will help with the
removal of the black smut.

Thanks... I didn't know that! I often wondered if there was an easier way
to remove the black residue.

Actually, a stronger acid works better (quicker). The "blackness"
seems to depend on the alloy and it may still take light rubbing to
get the stubborn stuff off. I'm neither a chemist or metalurgist but
in my early days in a real engineering lab environment we had a "chem
lab" where they had tanks of caustic and acid (and Alodine) for
passivating aluminum and I learned a few things there. Always
remember to fully rinse any of this stuff off with lots of water.

[snip]

Awhile back I heard that after the metal is finished in a lye bath then
boiled in a solution of color dye (RIT) a colored, metallic finish, can be
produced---one of these days I'll try it on a scrap piece.

Now you're starting into anodizing. See:

http://w3.uwyo.edu/~metal/anodizing.html

On simple projects I print or photocopy text then affix them onto to the
aluminum surface (after a first coat of acrylic on the aluminum) with white
glue then with multiple sprays of acrylic affix them permanently to the
surface. It worked real nice with a bandpass filter project---I secured the
graph of the filter characteristics onto the minibox for reference.

Nice idea. I use the ruboff lettering (Datak) but of course they
don't have any BPF response curves, [g]