[Alt-photo] Split exposure of cyanotype

Loris Medici mail at loris.medici.name
Mon Jan 29 07:04:09 UTC 2018


Hi John, looks like you're experiencing bronzing / solarization due to
overexposure.

Probably some dark reaction occurs between the first and second halves of
the exposure, therefore you experience overexposure even if the total
exposure time was equal to when you don't split exposure in two parts.

If Dmax under the negative is gook / OK there's nothing to worry about,
unless you also need borders with good Dmax.

In order to open up shadow tones, I would fiddle with my curve instead of
following this strange (to me) protocol...

Regards,



2018-01-29 1:18 GMT+03:00 John Isner via Alt-photo-process-list <
alt-photo-process-list at lists.altphotolist.org>:

> I am relatively new at alt process in general and cyanotype in particular.
> I'm using Ware's formula on Cranes Cover 90 lb Wove, exposing in the sun
> with a UV integrator meter, and following all of the instructions that came
> with the New Cyanotype kit.   I also carefully followed the steps in Ron
> Reeder's chapter of Christina Anderson's Gum book to determine exposure
> time for maximum black, the optimal negative density, and a curve for
> correcting the midtones.
>
> On page 183 of Christopher James' 3rd edition, James suggests that you can
> get improved shadow detail by suspending exposure midway through, keeping
> the print in the dark for 15-30 minutes, then returning to UV for the
> remainder of the exposure.  I found that this technique definitely improves
> shadow detail.  James also says you should not "lose D-max integrity" but I
> did not find this to be the case.  My overall print seemed lighter.  The
> borders, where the paper is fully exposed to UV, are somewhat lighter than
> the borders of a print made in one go.
>
> If a split exposure is supposed to retain D-max integrity, then I'm
> guessing a longer exposure is needed.  If so, do I need to make a separate
> determination of exposure time under split exposure conditions?  Or is
> something else going on here?
>


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