From: Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Date: 06/19/00-05:45:37 AM Z
Nick Makris wrote:
> ... The Potassium Chlorate added by B&S to their B solution of Ferric Oxalate
> is at the concentration of 1.32%. With a normal negative and equal drops of
> Solutions A & B that would equate to a .66% sensitiser. Therefore,
> affecting the sensitiser for a normal 8X10 negative (24 drops, 12 of each),
> via the single drop of PC method will require a concentration of _____%????
> ...
The two cases are as follows (PC= Potassium Chlorate):
1) 12 drops sensitizer solution A plus 12 drops sensitizer solution B
(assumed to contain 1.32% PC) plus 24 drops metal solution = a final PC
concentration of 0.33% in the coating solution (48 drops).
2) 24 drops sensitizer plus 24 drops metal solution plus one drop PC.
What is the concentration of the drop of PC?
Note that the scenarios produce slightly different amounts of coating
solution. The final PC concentration for case 2 (49 drops) should be
0.33% to equal that of case one. This means that the concentration of
the drop of PC should be 49 times 0.33 or
16.17%
This resulting amount of PC (using a drop of 16.7%) is far too great and
will likely harm the paper or image.
This amount of coating solution (49 drops) is typical of what I would
use for an 8x10 with a paper such as Bienfang 360 (I use 57 drops for
Crane's Cover-90). Typically for an 8x10 if I use PC solutions (I use
the one drop method, case 2), the PC is at strengths ranging from 0.5%
to 2%. For the Bienfang (8x10 using 49 drops) a PC concentration above
2% will show degradation. For the Cranes (8x10 using 57 drops) a PC
concentration above 3% shows degradation.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
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