>...
> Now for the risky part--attaching the mirror. As Steve Scampini
>noted, acetic acid and Aluminum are not combatible.
Perhaps a real chemist can confirm this, but I think you can immerse an aluminized mirror in undiluted acetic acid and nothing will happen. In fact you can drown it in nitric acid and most other acids and nothing will happen because alumimun becomes passivated by its ferociously strong oxide layer. I know vinegar, which is about 5% acetic acid, won't do anything. I've tried to strip aluminum off glass with common laboratory acids and most didn't have any effect at all. I did discover that 10% nitric acid is great for cleaning a spotty coating to near new condition but it won't remove it. HCl will dissolve it though.
> Two days later I carefully tested the bond--it was quite strong!
>I let the assembly sit for a few more days before removing the plastic
>seal. In checking the front surface I noticed a few wisps of purplish
>discoloration near the edge which were not present before I began the
>operation. I used regular scotch tape to hold the plastic onto the mirror
>and it did not remain comletely sealed, so I suspect that some acetic acid
>fumes leaked under the plastic. I doubt the effects will be noticeable,
>but if I were to do it again I would use thin strips of duct tape and
>possibly run a fan over it as it cured. There was much stronger dis-
>coloration on the sides of the mirror which had some aluminum coating on
>them and which were completely exposed to the fumes, so I would definitely
>recommend protecting the front surface of your mirror if you use acetic
>acid based silicone rubber adhesive.
>...
The purplish color makes me wonder if it isn't simply some volatiles being deposited so that your multi layer coating is thicker and becoming spectrally "detuned". If that's so it is probably an organic that will wash off with some solvent. I dunno if I'd risk messing with it now--your black marker pigment will dissolve and redeposit, and you should check with the coating people in any case--but after the newness wears off you might try it.
Aart M. Olsen aart@uiuc.edu 217-333-7467 College of Veterinary Medicine Univ of Illinois at Urbana-Champaign