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RE: Blotchy Mirror Coatings - Bob May Are You There?

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Posted by Rick Crockett on October 2, 2000 17:07:27 UTC

Hi Bob,

I didn`t see Bob May at the ATM Class Sat. so he may be away. Meanwhile I`ll try to help.

You didn`t say how long it was between painting the tube and reinstalling the mirrort but if you allowed Krylon a couple of hours, I doubt there was a reaction there.

Is this an enhanced coating? The standard coating are almost impervious but enhanced coating tend to be chemically sensitive. Most cases of blotchy that I have seen have come from salts in the water or air near coastal areas. Many enhanced coatings are hygroscopic and will hold some of the moisture and salts from cleaning. What did you use to clean the mirror? My first guess is that you have an enhanced coating and you did not use distilled water.

A re-cleaning may help, if you feel so, do this:
Apply as pure an alcohol as you have and see if the blotch clears. The whole surface needs to stay wetted until it does. Then follow with a warm solution of 80% distilled water, 19+% pure alcohol, and a drop (one drop) of dishwashing solution. I prefer to warm the solution and apply at about 100f. If this doesn`t work then let`s discuss other options.

Since this is an old scope for you, how does the performance compare now? A lot of times blotchy coatings will still perform very well.

Good Luck,
-Rick

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