Sil Horwitz (silh@iag.net)
Fri, 05 Mar 1999 16:52:19 -0500
At 99/03/05 01:50 PM -0700, Bob_Maxey@mtn.3com.com wrote:
>
>Despite contrary opinions, spin coating can work well. My father used this
>method years ago when he made albumen emulsion plates working in the
>Blueprint business. The problem is that it is difficult to coat large
>surfaces and to control thickness. Make sure you test all the variables.
>You might also consider buying a motor and mounting it in a plastic or
>metal tub. That way you can add a lid or ideally, a clear Plexiglas cover.
There used to be a toy that had a spinning disk (battery operated) on which the
user put a sheet of paper and let drips of paint fall on it to make a "modern"
painting! It was too small to do much, but I tried to coat some 4x5 paper and
couldn't get a smooth surface. Don't recall the speed, but it wasn't anywhere
near what the photoengravers use (or used) to coat plates. I also tried coating
with printed circuit board resist, and couldn't get a good flow, either.
Someplace in the literature there must be data on the speed necessary, etc.
Industrially, coatings are made mostly by extrusion through small slots, with
"air knives" to give the precision necessary. Coatings can be made down to very
tiny fractions of a millimeter; very necessary with color films which today
have twenty or more layers in the emulsion.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net
Visit http://www.psa-photo.org/
Personal page: http://www.iag.net/~silh/
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