U of S | Mailing List Archive | alt-photo-process-l | Re: Mottling in lighter tones in cyanotype?

Re: Mottling in lighter tones in cyanotype?

See inline comments...

22 Ocak 2009, Perşembe, 10:24 am tarihinde, Brian Pawlowski yazmış:
>> Try another paper / another batch of the same paper... (COT 320 is
>> wonderful for instance.)
> I'm going to kill myself:-)
> I switch to Platine because Crane's and COT 320 were staining in
> highlights...

Never experienced staining with both COT 320 and Weston Diploma. I was
getting runoff (as you name it) / bleeding but the final print was good
w/o any stain. (Because I calibrated taking into account the runoff?) No
runoff with new cyanotype. (Or very little, when compared to traditional
cyanotype.) Maybe you should switch FAC and use from another supplier.
(Mine is from B&S, purchased in 2003...) FAC is ill-defined and its
properties differ from supplier to supplier / batch to batch... (That's
another good property of new cyanotype, you use very defined compounds for
mixing new cyanotype sensitizer.)

>> 10 minutes of air drying (at max.) is enough if you force dry the paper
>> later; you need the sensitizer in paper, you can start to blow hot air
>> as
>> soon as the surface shine is gone...
> Would speeding up the drying change it - I would think air drying
> would allow emulsion to absorb more.
> I'm just trying to puzzle why this might affect my mottling (I'm with
> you on emulsion coming off surface?)

When the surface shine is gone the sensitizer is fully soaked into the
paper, so there's no point in waiting more than this to force dry the
paper -> it's inutile loss of time. This is nothing to do with mottling ->
it was a side note letting you save time and be more productive ;)

BTW, do you blow the back of the paper also? Dry both the front and back
of the paper (on a clean surface when the paper is emulsion down) to rule
out uneven moisture possibility (that can cause mottling, but less likely
when you wait 1h - this is more important when working quick)...