Re: Image formation in gum

From: Tom Sobota ^lt;tsobota@teleline.es>
Date: 12/16/05-05:05:24 AM Z
Message-id: <7.0.0.16.0.20051216113511.021b9e40@teleline.es>

These days I think that nothing surprises me anymore, but I agree with you that cleaning a glass surface is not easy. Years back I re-silvered the mirror of a Rolleiflex in a vaccum chamber used for plating specimens for electron microscopy. I used aluminum. I still remember cleaning and cleaning again the glass with solvents, ultrasound bath ... It was worth it: now, 25 years later, the mirror is still like new.

The glass is regular window glass that I have cut in small sizes (i.e. 10" x 8") just for this kind of experiments. As such, it certainly will be float glass. The lamp I use for exposing emits too much visible light for the fluorescence emitted by the tin to be seen. But thanks anyway for the info.

Tom Sobota
Madrid, Spain

At 10:45 16/12/2005, you wrote:

>>>I cleaned the glass ... the first time. But after a first (failed) exposition I reused it, and this time I didn't bother to clean it very carefully, so the surface was only visibly clean. I'm also not sure how can this change the results, but just in case next time I will clean the surface better. Also, Jack's considerations about back reflection are noteworthy.>>>

 

I am not saying it will or can change your results. However, it is something to consider as you experiment. Removing the variables is very important in any experiment.

 

I make mirrors. Silver, gold, antique, copper, and galena (blue). The process will fail if the surfaces are not spotless and you would be surprised to know that it can be quite difficult to thoroughly clean a glass surface. Small errors do make a difference and I really cannot tell you if a "dirty" surface will in any way affect your end result.

 

>>>Now that you mention it, is there any practical reason to use one or the other side of a float glass for coating? And if so, how do you distinguish them?>>>

 

Float glass (window glass, for example) has two sides: the "air" side and the "tin" side. UV light will usually reveal the tin side due to the fluorescence caused by tin "contamination." This means that one side is chemically different than the other side. You did not say (or you did and I missed it) where the glass came from. If it is an old piece you found somewhere, who is to say what condition it is in. It might be free of any tin contamination

 

Bob

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Received on Fri Dec 16 05:07:10 2005