Carl Weese (cjweese@wtco.net)
Fri, 21 May 1999 11:44:43 -0400
Jeffrey,
I missed the part about the dichromate. In fact I prefer to make
negatives that print with no contrasting agent at all because this
results in the smoothest tonal transitions in the print, but I've never
seen blotches resulting from use of ammonium dichromate. Also, if I read
your message right you are using a single drop of .5% ad in 48 drops of
solution which I'd call inconsequential. I consider a drop of 2% to be a
small dose for an 8x10 coated with 24 drops total--that's four times as
strong a hit. This gives something roughly equivalent to a half-grade
contrast difference in silver paper. I'd be surprised if there is any
visible difference between nothing and .5% in 48 drops.
The primary difference between potassium chlorate and ammonium
dichromate when used in the zia method is that the pot. chlor. is merely
a highlight restrainer, while the a.d. is a true contrasting agent that
increases tonal separation throughout the tonal scale.
---Carl
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