Re: Cooking in glass mounted slide

[P3D Cliff Howard <Cliff.Howard@xxxxxxxxxxxxxxxx>]

P3D dalia miller wrote:
> 
> In a galaxy far far away, I read something by H. McKay, whereby he stated
> that the transparency chip "cooks" when placed inbetween 2 pieces of glass
> and projected.  And that he doesn't recommend ever mounting in this manner!
> 
> However, I don't remember where I read this. Any help would be greatly
> appreciated.
> 
> dalia

The following is a quote from "The Source Book,
Kodak Ektagraphic Slide Projectors"

Transparency Life

"In general, transparencies kept in open-frame mounts
can be expected to last longer than those kept in glass
mounts. A transparency mounted in glass has a thin
insulating layer of air between it and the glass, and the
heat from the projection lamp must be transmitted
through the layer of air on each side of the
transparency, and then through the glass. The
transparency will get hotter before the temperature
stabilizes than will a similar transparency in an
open-frame mount. With an open-frame mount, the
heat is carried away by air moving over the
transparency surface."

Sounds like the same principle that's used in double pane windows.

Cliff Howard


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