Chris wrote:
>
> It seems, then, that after a certain point the amount of dichromate may
>not make that big of difference, except to reduce contrast which is not a
>good thing--which is what Sandy said is true of carbon and gelatin anyway.
>(In fact, in Sandy's carbon demo to us photo grad students a couple weeks
>ago I was shocked to find out the incredibly low strength of am di he used
>to sensitize his paper--like, was it, Sandy, 1/2%???)
Chris,
You are correct about the 1/2% solution. That is what I typically use
to sensitize carbon tissue for printing with negatives that have a
density range of about 1.5.
There is also the issue of how much of the sensitizer is actually
utilized by a process. In the case of carbon, for example, I
typically sensitize about three 14X20" carbon tissues at a time, or a
total of about 840 square inches. At the end of a sensitizing session
I replenish the sensitizer with whatever amount is lost during the
session. For three sheets of the above size the amount of sensitizer
lost is approximately 100ml. Of this amount I estimate that
approximately 75% is absorbed by the tissue, with the other 25% lost
during squeegeeing. Which is to say, I am actually using only about
25ml of a 1/2% solution per 14XX20" tissue. By my calculations that
amounts to about 0.13g of dry dichromate per 14X20" (280 square
inches) tissue.
Sandy
Received on Thu Nov 27 11:45:37 2003
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