Notes on Polycarbonate ground glass

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From: John Cremati (johnjohnc@core.com)
Date: 08/23/02-02:12:33 AM Z


>
> > N1861@aol.com <N1861@aol.com> wrote:
> >
> > Has anyone made a ground glass from acrylic or polycarbonate sheet,
> > as a
> > lighter weight alternative to glass?
> >
John Cremati wrote:

My concern would be the warpage of the polycarbonate sheet on a larger view
camera as well as cleaning.....I have etched decorative designs into
Plexiglas on many occasions as commercial artwork.. I have noticed several
things about it.. I would think the huge advantage is that is very light
weight , resists breakage, and my guess would be that once etched it
should produce a great image as the etching seems to be extremely fine
grained ...
 1) After removing the protective cover wrapping the plastic seems to have
a static electrical charge that attracts dust. This is very obvious after
sandblasting, during which electrical fields may even become visible on the
Plexiglas.. I usually have to flood wash the plastic when thru etching and
this seems to neutralize the static electricity...
2) the plastic will warp or expand dramatically with temperature
change..It may be wise to mount in a floating frame...
3) Plexiglas may become yellow with age.. a better grade of polycarbonate
may be in order and should be researched..
4) The Plastic scratches very easily ...Special cleaners are used to
minimize this as well a keep the plastic from yellowing.. These cleaners may
get into the pores of the etched surface and may cause streaking, staining
or a blotting appearance...This happens so much that on my decorative work
I always use a separate plastic cover plate over the etched surface to
protect it sandwiching the engraving......
5)During the sandblast process the plastic requires several passes as it
does not sandblast easily .. This may be the reason for such a fine grained
appearance when finished..The plastic probably resists the sand blast action
and only allows for minimal penetration into the plastic surface.......
Happy Trails,
John Cremati

>
> No, but I don't see any reason why not. Most interchangeable focusing
screens
> for 35mm & MF SLRs are made of some sort of plastic.
>
> Wayne Harridge

>


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