Re: Cleaning mirrors

Jaakko T Oksa (joksa@snakemail.hut.fi)
Thu, 6 Apr 1995 02:19:53 +0300 (EET DST)

On Wed, 5 Apr 1995, Bob Bond wrote:

> My shiny new mirror is getting dusty and dirty. I tried blowing some
> canned air on it to clean it off and ended up with a blueish haze where
> the air hit the mirror. I intend to take the mirror out of the mount,
> soak it in a bathtub with a little dishwashing soap, then rinse well
> and wipe lightly with lens cleaning tissue and Edmunds Sci. lens cleaning
> solution. Will that take care of the blue haze from the canned air?

I have similar experiences regarding canned air (or cfc). I never use it any more.

The most important thing to remember is that aluminized optics should only be cleaned using close to neutral detergents. Dish washing liquid is fine. The second most important thing is not to soak the mirror for longer than what is neccessary. And finally, even though mirrors usually have a SiO2-overcoat, cleaning tissues and such should not be used. The general concensus seems to be that the best method for mechanical cleaning is to use wet cotton balls and zero pressure while the mirror is wet.

By the way, I don't think you need to worry about a little dust on the mirror. In my experience mirrors look awful when the surface is illuminated from a suitable angle, but the dust doesn't affect image quality. I usually clean my mirrors once a year, and even that would not really be neccessary. I have never seen a mirror that would significantly absorb or scatter light because of dust, even though I've seen many that have looked truly awful when examined in bright light.

Jaakko Oksa