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cleaning glass revisited

I'm new to this discussion site, but the archived messages for "cleaning
glass" reeled me in.  Who else would care?  I'm behind the game, but wanna
register my comments anyway.

I have the same hazy "film" residing on my glass panel beneath my light.
As mentioned by other sufferers, it's resistant to scrubbing with vinegar
and HCl (I work in a lab and tried HCl, acetic acid, and even concentrated
NaOH out of frustration).

Whatever the chemical genesis of this haze, I don't think that it's a
deposit ON the surface of the glass.  Rather, it may be a deposit WITHIN
the surface of the glass!   I imagine that glass surfaces have a certain
porous nature and that salts from splashed water are being drawn into
little pores as the bulbs heat the glass and drive off the water.  This
would leave a minute salt deposit in the pore that could wreak havoc with
the transmission of light and masnifest as the mysterious film.  Has anyone
ever soaked their glass for a few days in acidic solution instead of using
direct attack with "elbow grease"?  (The hypothetical compounds in the
pores would have to be resolubilized and diluted out of the pores.)

And no one mentioned that, when wet, the glass may appear  CLEAR--i.e. free
of haze.  So alot of people may have this irreversible haze but mistakenly
believe they are removing it everytime they wash their glass because it
seems to disappear when wet.  This optical effect of the water may also
explain why the aquarium sides do not appear hazy; you wouldn't know if the
side glass is being affected unless you drained and dried your tank.  (I
recently broke down a 15 gallon tank and the glass had a cloudiness to it
that I never noticed when the tank was in operation.)

The idea of wrapping the glass panel in plastic wrap was brought up, and I
had considered it awhile back.  Definitely a good means of protecting the
glass, but have you ever tried to hold up a piece of saran wrap and look
through it?  Every little wrinkle in the wrap reflects light in various
directions.  Reflected light isn't going to promote plant growth.  So one
may want to wrap carefully and double-check that you're not introducing a
greater interference in the light's path between the bulbs and the water.
(Can you see your fish and plants clearly through the wrapped glass?)

I finally decided to just take out the glass panel and let my bulb and
light fixture take the brunt of high humidity and condensation!


Carmen C. Robinett, Ph.D.
Dept. of Molecular and Cell Biology
401 Barker Hall
University of California
Berkeley, CA 94720-3202
(510) 642-5971
FAX (510) 642-7846