[alt-photo] Re: no shrink, no size tricolor gums

[Loris Medici]

Maybe it's a paper / surface issue? I use (was using actually)
gelatin sizing, strength 3%, hardened with formaldehyde, now I use PVA
glue (hightlights clear much faster)...

BTW, since I don't use negatives specifically calibrated for gum
dichromate (I use cyanotype negatives for gum), my criterion isn't the
merging of the first two steps in a step tablet test; I just aim to
find a pigment/dichromate/exposure combination that gives me empty /
clear specular highlights after 30 minutes still water development,
that's all. I start with the highlights, and build up density (in the
shadows) with subsequent layers. I never tried to calibrate digital
negatives for gum so that I will have a perfect single layer print;
that doesn't make sense to me, since I work in multiple layers and
prefer (much) to use gum's flexibility in order to achieve my goal...

Regards,
Loris.


2010/9/14 Charles Ryberg <cryberg at comcast.net>:
> Loris--I would love to get my wash times down to 30 minutes, but I don't
> know how.  I determine exposure with 21 step strips--find the exposure which
> merges 1 and 2--multiply by .7 and get, depending on color, between 2 and 5
> minutes.  The trouble is, I don't get paper white for an hour, maybe and
> hour and a half.
>
> So, am I using too much or too little dichromate?  too much or too little
> pigment?
>
> I'm doing some tests this week, but any advice is welcome.
>
> Charles Portland Oregon
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