[acidrain]

Once you have an established, consistant, temperature controlled tank, there is a way to do runs starting in CV, then switching to CC which will allow you to skip measuring surface area. We can talk about that later... you're not there yet.

DMiom brings up good points... the etching process is probably too vigorous, and will affect the color.

Different alloys act differently as far as that natural gold color. 6061 pretty much has no color.

Try doing a test piece withouit the etch/desmut steps... just degrease and go.
Be sure to seal afterwards.