Re: acetone

Sandy,

The amount of dichromate and its concentration is a variable I have kept
constant in my experimenting with the process -- and have only used the
pigment concentration (and neg contrast) as my source of contrast control.
This dates back to when I first saw a relief in a wet print and thought of
ways to increase the relief.

So with my low pigment concentration, and the additional lowering of the
contrast due to a relatively large amount of dichromate in the tissue (thus
lowering the contrast even more), I have been pushing my exposure and
development of my negatives to be very high in contrast (a good carbon
negative, for me, will not print in the standard pt/pd process -- it will be
too contrasty).

Actually, the scenes I want to photograph for carbon printing have tended to
be of high contrast (such as sunlight thru the redwoods), so my way of
processing has suited me well. I like scenes that I measure 7 to 13 stops
in! The scenes that are 7 to 10 stops in range I give extra development to
-- 13 stops scenes I get to process at the "normal" time/temp.

I thank you for all the help and encouragement you give all us printers. I
should revisit some of my negs that make good pt/pd prints and try a lower
concentration/amount of sensitizer. Sounds like I could get relief from
those lower contrast negs using less dichromate, that I could not when I use
my "standard" sensitizer.

Just to be sure that I am on the same page. I use an 8% stock solution of A.
dichromate that I dilute 1:2. If my way of figuring it is correct -- I end
up with a 2.7% solution. Roughly..if I start out with 8 grams of A. dichro
in 100 ml water then dilute it 1:2 by adding 200 ml acetone, then I end up
with 8 grams of A. dichro in 300 ml liquid. 8 divided by 300 is about .027
or 2.7%. Not too far off from yours.

Or do you start off with a 1% or 2% stock solution that you dilute 1:2? I
am sorry, I know you just put this info out on this list, but I do not have
those posts availible.

vaughn
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Received on Fri Dec 22 13:12:14 2006