At 11:44 PM +0000 4/23/02, olympus-digest wrote:
>Date: Wed, 24 Apr 2002 09:01:35 +1200
>From: "Brian Swale" <bj@xxxxxxxxxxxxxxx>
>Subject: Re: [OM] Old Oly OM Re-silvering prisms
>
>Gareth asked about re-silvering prisms.
>
>About 3 months ago there was a discussion about this and it seemed that
>there is a place that does that, as well it also seemed to be not outrageously
>difficult to do at home.
>
>I can't remember if I read it in this group or another tho'
>
>I wonder if Joe Gwinn contributed on it? (Copied to Joe)
Guilty. The original posting follows:
At 11:52 AM -0500 12/21/01, Joe Gwinn wrote:
>To: olympus@xxxxxxxxxxxxxxx
>From: Joe Gwinn <joegwinn@xxxxxxxxxxxx>
>Subject: Re-silvering old pentaprisms
>
>There has been some discussion of how to deal with pentaprisms with damaged
>silvering. It appears that there are no more spare prisms available.
>
>I would comment that if the glass is undamaged, which is likely the case, it's
>easy to strip the silvering and re-silver a prism.
>
>Stripping: Simply immerse the prism in Nitric Acid until clean. This is the
>standard approach, and will strip the paint and the silvering, and will not
>harm the glass.
>
>Resilvering. There are two approaches, true silvering and aluminizing. It's
>likely that the pentaprisms are aluminized, not silvered, but for repair
>either approach will work. Protect surfaces not to be silvered with varnish,
>which is later removed by soaking in acetone.
>
>
>Silvering. With metallic silver deposited from solution, the traditional
>silvering process. This can be done one prism at a time in one's kitchen or
>basement using "Brashear's process", and is documented in many places, such as
>in 1960's editions of The Handbook of Chemistry and Physics, and old books on
>making telescopes. I don't recall the details, but Silver Nitrate and Nitric
>Acid are involved. The process is quite simple and robust, but absolutely
>clean surfaces are required. Thus the use of Nitric Acid to clean the glass.
>
>More recent books omit chemical silvering processes, because vacuum
>aluminization pretty well displaced all use of silvering.
>
>
>Aluminizing. One sends the optical goods off to a company that does it for
>you, unless you have enough aluminizing work to do to make purchase of the
>equipment worthwhile. Amateur telescope makers (ATMs) make their own mirrors,
>and then send the mirrors off to be aluminized. Look in the back of magazines
>like "Sky & Telescope" for the ads. There are probably newsgroups and
>reflectors for ATMs. Some ATM books have the receipe for silvering as well.
>
>It's cheapest to have a bunch of prisms metallized at once. It isn't terribly
>expensive in any case.
>
>
>Back paint. Whichever kind of metal is chosen, especially if it's silver, it
>must be protected with a coat of black paint. Suitable paints are sold to
>Glass & Mirror shops. If one has aluminizing done commercially, one can have
>the coater do the painting as well.
>
>
>Anyway, don't throw those old prisms out. Collect them and re-silver them.
>
>
>Joe Gwinn
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