At 7:35 PM +0000 1/31/02, olympus-digest wrote:
>Date: Fri, 1 Feb 2002 00:25:50 +1300
>From: "Brian Swale" <bj@xxxxxxxxxxxxxxx>
>Subject: Re: [OM] Cleaning oily films off of glass
>
>Hi Don,
>
>Thanks for your thought. I actually got there fine with industrial strength
>methylated spirit with no additives I could see.
>
>There were other suggestions from the list; perhaps the most meritorious
>were for that window-clean blue solvent "Windex"; or Windolene" made by
>Johnson & Johnson.
>
>Using any detergent that behaves like a dishwashing detergent would bother
>me a lot. They leave their own sticky deposit. From years of experience hand-
>washing dishes <g> especially trying to get wine-glasses free of detergent, I
>know it requires lots and lots of rinse water to shift the detergent after it
>has
>done its job. And even then one can't be quite sure. They stick around for
>yonks. So how would I get lots and lots of rinse-water in the back of a lens
>and out again without causing extra problems? And would the detergent
>sneak around the side of the lens in the mount and give rise to a new set of
>problems?
Yes. It's very hard to get glass (or china) really clean by hand washing,
because one cannot use hot enough water if one uses bare hands. I have had
great success wearing medium-thick cotton-lined rubber gloves (Bluettes in the
US, available only at hardware stores) and using water at 60 degrees centigrade
(140 degrees farenheit), which is scalding hot, hot enough so the grease just
vanishes. A hot rinse is required to get all detergent residue off.
In the US, many hot water heaters have been turned down to 120 degrees
farenheit (49 degrees centigrade) "for safety", making it almost impossible to
get glass clean. The traditional setting was 140 degrees farenheit, and
restaurants set the temperature to 150 or 160 degrees farenheit, to cut the
grease. I've heard of 180-degree hot water sprayers at special stations
intended for cleaning deep-fat fryers. With water this hot, one must be very
careful.
Bosch dishwashers wash and rinse at 140 to 160 degrees farenheit (60 to 72
degrees centigrade), depending on the wash cycle chosen. The rinse is often
hotter than the wash. The dishwasher heats the water itself, so the inlet
temperature has no effect other than slowing things down if the inlet water is
cold.
I don't know that a lens would survive this kind of treatment, but it works
great for 24 0.000000e+00ad wineglasses and the like. Lenses are far thicker,
and may not handle the thermal shock without shattering. It could work if one
removed the lens from its cell and heated the lens up slowly, but I don't know
at what temperature the cement used to glue cemented doublets and triplets
together loosens. Also, thermal shock is a traditional way to pop cemented
doublets and triplets apart into individual lenses.
Joe Gwinn
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