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

My experience concurs with Clay in most respects--all my negs range from
emerald to blue green except when working with bw papers which of course use
different colors. The actual color chosen will vary with printer and
process--students are using the Epson 4000 and I the Epson 2200, and we
don't always pick the same color.

However, that said, I think cyanotype has a different response to color than
other processes, maybe having more of a choice of colors to pick from that
will hold back light. Especially in comparison to salt or vdb or
argyrotype, for instance.

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

----- Original Message -----
From: "Clay" <wcharmon@wt.net>
To: <alt-photo-process-l@usask.ca>
Sent: Tuesday, February 21, 2006 7:11 AM
Subject: Re: spectral sensitivity of platinum/palladium and cyanotype
coatings.

> The fact that green negatives are most efficient at blocking UV is
> old news for many of us. There are at least three different
> approaches that have gone way beyond idle speculation and have proven
> this empirically.
>
> Mark Nelson's system, Keith Schreiber's investigations and my Ternary
> diagram approach to discerning UV spectral density all generally end
> up showing that greenish ink colors tend to be the most efficient at
> blocking UV light.
>
> see:
>
> http://www.precisiondigitalnegatives.com/
>
> and
>
> http://www.zianet.com/jkschreiber/articles/1280PyroDigiNegs.html
>
> and
>
> http://www.alternativephotography.com/articles/art056.html
>
> As far as implications for spectral sensitivity of pt/pd, I would
> surmise that it says very little. The UV blocking characteristics of
> printer ink has more to do with the characteristics of the ink itself
> than with the platinum process per se.
>
> 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.
>
> Clay
Received on Tue Feb 21 09:39:06 2006