Tinted glass plate negatives

Deborah Tint <dtint [at] verizon__net> writes

>I am scanning a set of 8x10 dry plate glass negatives dating from
>1910-1937.  We are scanning them to create positive digital
>"prints". In some cases the whole plate or selected areas have been
>painted on the emulsion side with a transparent deep magenta
>material.  ...

The dye used was water soluble 'crocein scarlet' and it was painted
on with a brush in varying densities on either glass or film
negatives to selectively lighten areas of the print. The effect
could be slight or severe depending on the density of the dye added.
This was still being done in photo labs throughout the 1980s. Doing
this once to the negative allowed the darkroom technician to make
identical quantity prints as opposed to individually hand dodging
each print.

I suggest you make an RGB scan, then simply delete the red and green
channels to get an approximation of how it would have looked on blue
sensitive paper. Better still, recent Photoshop versions have a
feature where you can add a black and white adjustment layer which
allows you to select the color filter for the conversion from color
to black and white. What you don't know of course are the exposure
and the contrast grade of paper used in the original printing, so
also post scan, you need to adjust the levels and use the best
looking 's' curve which should be done as two adjustment layers.
That makes a three layer adjustment set which you should archive
together with the underlying master scan so your interpretation is
non-destructive and the original raw scan is always available down
the road.

John Castronovo
Techphoto, llc
Boonton, NJ


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                  Conservation DistList Instance 25:47
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