Re: POP paper from regular photo paper

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From: Liam Lawless (lawless@ic24.net)
Date: 01/23/01-07:15:52 PM Z


Not really. Papers that are not suitable for printing out remain
unsuitable, while those that do work do not really benefit from a silver
bath. Probably because most papers now have a supercoating that inhibits
interaction between the emulsion and the silver solution. There may be a
slight enhancement of printing speed and D-max, but also reduced contrast
and increased likelihood of fog and stains.

In my experience (which ain't much), chlorobromide papers are the ones to
use - presumably those with the highest chloride content. To test, expose
small samples to daylight/UV (without a negative) and choose the ones that
darken most &/or produce the most attractive colours. Kentmere Art Classic
was the one I used to use most (don't remember the others, though I believe
Kentona was also a good one). AC was one of the slowest to print and gave
an orangey tone that I didn't particularly like, but it turned a fine,
delicate blue with gold toning.

As with "straight" silver POP, fixing is the most likely problem area. To
minimise density loss, make your fixer alkaline. Do not use a rapid (amm.
thiosulphate) fix, but ordinary hypo (sod. thiosulphate). And not too
weak - 5 minutes in 100 g of hypo crystals plus 10 g sod. carbonate in a
litre should be fine. Do not overwork - I'd suggest about a dozen 8X10s per
litre.

Liam

Important PS:
Clerc himself suggests soaking old or fogged bromide or chloride papers in
about 0.5% silver nitrate solution (or in one of several reducers) to make
them suitable for printing out. This is what I tried, several years ago.
Papers were obviously different in his day, and one obvious difference is
the supercoating.

However, something else in Clerc may be more promising: the possibility of
intensifying faint POP images by exposure to orange or red light. He says:

"The sensitive film of print-out papers is not affected in the least by the
light which passes through a red, orange or deep yellow filter, even on long
exposure to sunlight, but the colloidal silver formed during a short
exposure to light under a negative plays the part of a panchromatic
sensitiser. The parts where an image has already been formed can,
therefore, darken during a second exposure, more where the silver has
already been formed than in other parts. The second exposure to light thus
acts as an intensifier (continuing radiation).

"This phenomenon, which was noticed in Daguerreotype images by E. Becquerel
in 1840, and which was explained by Luppo-Cramer in 1909, is of particular
importance if soft prints are required from very vigorous negatives; in this
case exposure under the negative should be carried just far enough to obtain
full detail in the shadows.

"The continuing action of yellow or red light can be used for increasing the
contrast of an image which has been made from a negative with weak contrast,
but in this case the second exposure should be made through the negative in
order to graduate the intensification of the image (H.J. Channon, 1909)."

From: ken watson <watsok@frii.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Wednesday, January 24, 2001 12:16 AM
Subject: RE: POP paper from regular photo paper

> Can one take "normal" paper and float it on silver nitrate solution and
> maybe have it work more like traditional POP?


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