Sounds like Sandy also got taken for a few hundred dollars of useless
materials:-) Ditto here, except it happened to me six years earlier, ca.
1974. This is why my motto is:
"Months in the lab will save you hours at the library"
>I agree with an earlier posting of Luis to the effect that the market is
>not there for commercial
>manufacture of the tissue. I have know several people who in recent years
>thought this to be feasible but after completing a market analysis decided
>they were better off throwing their money in another direction.
preferably *my* way:-)
>
>As for the problem of fog, perhaps we can add some specificity to the
>discussion. First, let us be clear that some pigments, for whatever
>reason, produce much greater fog levels than others. Try to identify and
>eliminate these pigments.
At one time I had to move and had to built a new darkroom with plywood. I
suspect that the aldehydes emanating from it were the cause of my fog
problems. I had to dry my materials asap and then use them quickly. The
same raw products didn't give me such trouble in my previous location
>
>In my own tissue there is a very low level of fog that I can not
>altogether eliminate, on the order of log .05 or so. That is, if the Dmin
>of the paper base on which a step tablet image is placed is log .06,
>about the lowest Dmin I can get from a carbon image in the highest
>high-lights is of the order of log .11. I do not find this to be
>particularly troublesome, because Dmin, though specific in a technical
>sense, is very relative from an aesthetic perspective. Ater about 6
>months, stored at room temperature, an identical tissue (same gelatin,
>pigments, dispersions, etc.) will have a Dmin level of between log .20-30,
>still usable perhaps with some negatives, but certainly marginal.
Yep, with monochrome you can get away with murder actually. I keep looking
for vintage carbons and one of the ways to identify them, in some cases, is
by looking at the fog band, usually 1 cm wide around the image. I collect
vintage prints for my students to examine and compare with current work and
I have a very charming photo of a child in carbon, made ca. 1910 as I
recall (it's dated but not at hand) in Boston, and if you look at the print
matted it looks excellent. You lift the mat and then see that there is a
very significant amount of fog, possibly 0.30 around the image, about 1 cm
wide (left there by the safe-edge) but since the paper was cream colored to
start with and the pigment color is of a warm brown, the whole print is
excellent.
Time and time again I have found that monochrome carbon prints with a
significant amount of fog had highlights that *appeared* very bright, on
account of the dark shadows which were very deep black. The fog band I
referred to above is left by that "safe-edge" around the image. When
everything is perfectly under control with very fresh material and
preferably pre-sensitized, that safe-edge area will show clear gelatin only
visible under a certain angle. Then you run a finger in that clear area and
you will see a difference in shinyness as you remove the soft gelatin. This
is as perfect as can be.
In practice however you easily get away with 0.20 or more and most workers
take a sponge and neatly remove this light gray area around the image. Do
practice this on a spoiled print;-)
Luis Nadeau
NADEAUL@NBNET.NB.CA
Fredericton, New Brunswick, Canada
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>Sandy King
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