Heat vs Air drying

John Barnier ( jb@dgi.net)
Tue, 07 January 1997 8:48 PM

Hello all,

As to the new cyanotype drying question, Mike Ware sent me the following
note today. His permission secured, I'm posting it here for the list:

>My tests on New Cyanotype show no significant difference in the step tablet
>prints between sensitizers dried under ambient conditions (about 20 C and
>55% RH for around one to two hours) and those dried in a stream of warm air
>(about 40 C for ten minutes), *Except* when the latter are printed
>'immediately' (i.e. within a few minutes) and not allowed to 'rest'. Then,
>the dried specimens show a measurable density loss, around 0.1 to 0.3,
>depending on paper and processing, which is most evident in the mid to high
>values. There is negligible effect on Dmax. I.e. the dried sensitizer is
>roughly one stop more contrasty, at most. I have not noticed any other
>degradation.

Mike also added an interesting twist to clearing the New Cyanotype:

BTW, I have now replaced the (optional) 2% w/v citric acid, as first
'development' bath, by 1% v/v hydrochloric acid (10 cc of the concentrated
acid to 1 litre of water). This is much cheaper and even more effective at
'intensification'. Indeed, because it increases the higher densities but
actually tends to cut the lightest tones, it affords a large measure of
contrast control at the wet-processing stage, which can be very useful.
Water 'development' alone gives a very long printing scale, about 16 steps
on a standard 21-step tablet (delta D about 2.4), which is shortened from
both ends by the use of 1% v/v HCl to a range of about 12 steps (delta D
about 1.8). Of course, HCl baths of intermediate strength, say 0.3%, give
intermediate contrast. It's a very cheap and easy control to apply.

Feel free to pass on this information to anyone who might appreciate it;
I'm only sorry I didn't try these experiments in time for your article,
which I am looking forward to seeing.

N.B. I don't know if any of the above applies to 'traditional' cyanotype -
I haven't tested it in this way - but I'm sure there are several devotees
on the Alt Proc List who will be able to give you the answer.


John Barnier
12560 Morris Trail North
Marine on St. Croix, Minnesota 55047
USA
jb@dgi.net

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