Re: spectral sensitivity of platinum/palladium and cyanotype coatings.

I also found that it was not possible to get quite enough density for
printing processes such as VDB and salted paper using just the color
inks of the PDN system with the Epson 2200 so I developed, in
corporation with some other folks, a Blend-a-Palette which allows one
to blend in Black ink with the other colors as necessary to create a
DR as required by the exposure scale of the process. People who use
PDN and who know Photoshop can figure out how to do this pretty
quickly.

I do find that the negative contrast as read with a UV densitometer
is quite close to actual printing density, at least with the Epson
2200, so if you know the exposure scale of your process, and have a
UV densitometer, using the blend palette allows one to determine the
best color mix very quickly, and it is also very accurate.

Sandy

>My approach is admittedly not as 'pure' in the sense of trying to find out
>which particular ink pair works the best. But I do think there is some benefit
>to using black ink to increase the UV transmission density for processes like
>Van Dyke and Salt. I have no difficulty at all making negatives with enough
>density range to print Van Dyke, which is something I found difficult to do
>using the straight PDN approach, especially on the 1280.
>
>One thing I haven't had the time or inclination to investigate is the fact
>that the ternary diagram I use has some colors that are 'out of gamut' for
>some printers. I suppose this could cause some non-linearity in the
>transmission density response as the amount of black ink is varied (By
>changing the saturation). It is not something that has yet caused a problem,
>though.
>
>The approach I have been using is certainly a 'stone knives and bearskins'
>method that may not be the last word in precision, but it works for me and the
>workshop students who have used it.
>
>Clay
>Quoting "Christina Z. Anderson" <zphoto@montana.net>:
>> I'd appreciate your further comments on what you said, though, Clay:
>>
>> " In the end, it doesn't really matter, since it is trivial to find out
>> > which colors are most efficient at blocking UV light for your chosen
>> > process"
>> :
>> Do you think think this is because of your use of black ink in the mix and
>> not just pure color? Because if using straight color, it becomes more
>> apparent that there are a narrowed few that will work in each
>> process...maybe with black ink this is not so crucial? I mean, I've seen
>> your pt/pds at APIS and they are gorgeous...
>> chris
>>
Received on Tue Feb 21 10:40:28 2006