Re: Image formation in gum

From: Tom Sobota ^lt;tsobota@teleline.es>
Date: 12/16/05-03:28:31 AM Z
Message-id: <7.0.0.16.0.20051216102223.021b7e58@teleline.es>

Bob,

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.

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?

Tom Sobota
Madrid, Spain

At 01:30 16/12/2005, you wrote:

>>>Now I have relatively little experience coating glass with gum, more
so when I don't want to use any substrate such as egg white which
could produce a better adherence but also possibly the same effects
of pigment 'absortion' as paper. So I used a piece of clean window pane.

I first tried with a layer which was too thin, so I washed it and
made another with twice the amount of powder carbon black I'd use
normally for paper, some 0.5g for 10cc of gum. This emulsion was not
overly difficult to extend on the glass.>>>

 

Standard float (plate) glass has two sides. One side comes into contact with a molten bed of lead during manufacturing; it "floats," hence the term "float glass."

 

Also, the glass should be washed until the water film sheets off the surface unbroken. Glass might appear clean, but quite often, it is quite dirty. Use polishing rouge or pumice powder and a strong detergent.

 

You might want to consider these facts and run more tests. I am NOT sure how these factors affect your testing, however.

 

Bob

...

 

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Received on Fri Dec 16 03:28:55 2005