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Re: Cleaning glass

Roger Miller wrote:

>......Anyway, this might lead to the possibility that Paul's covers were made
>from an unusually soluble glass formulation and that the problem might be
>avoided by using a different kind of glass.

I get window glass, and that is probably soda lime glass, which, according
to "A Resource for Glass", http://www.cmog.org/Education/edglass.htm, is
the least expensive, and makes up 90% of the glass made.  Its resistance to
chemicals is "only fair".

The patterns of deposit are roughly circular and correspond exactly to the
size of the condensation drops that form every night.  Someone asked, if
glass is so soluble, why isn't there more etching of the walls of the
aquarium?  One reason may be that the water in the tank may have silica
already dissolved in it, and, in fact, may be near saturation with silica.
On the other hand, the condensate that forms every night is pure water with
no silica, and so it dissolves more from the cover glass.

I think we have done enough arguing about whether or not it dissolves.  It
does, and it redeposits, and the deposit is extremely hard.  Sometime I am
going to try a clear acrylic spray on the bottom of a tank cover and see
whether or not it protects the glass while staying clear and not poisioning
my plants and other tank inhabitants.  I may also try polyurethane.

Paul Krombholz, in soggy central Mississippi,  expecting some light frost