Re: pyro question


Cor Breukel (cor@ruly46.medfac.leidenuniv.nl)
Tue, 06 Apr 1999 16:57:11 +0200 (MET DST)


On Tue, 6 Apr 1999, Jack Fulton wrote:

> Cor
> Are you talking about a negative already developed? Or just going through the
> normal pyro process. If the former, exaclty how'd you do it?
> JF

Hai Jack, I've told this before on the list, but it is no problem to
repeat it, since I think it's a very usefull tool: I'll quote from a post
from Michael Gudzinowic, who very kindly helped me out on my weak
negatives..

<quote>
PMK pyro is the developer which I frequently use for medium and large
format work, and for Tech Pan (diluted 1:1). You won't be able to
increase the density range up to 2.2 from 1.3 with pyro. If you want to
try to improve the negatives you already have, make sure that they are
well washed, and bleach them in a solution containing 10 g/l potassium
ferricyanide and 10 g/l sodium bromide (potassium bromide works
equely well, as expected -Cor-)which will convert the silver
image to silver bromide. Then wash them again to remove all of the
ferricyanide (bright yellow). After washing, develop them to
completion (10-15 min) in PMK pyro, which will add the stain. Test the
apparent density by printing the negative - a densitometer reading won't
be accurate. If the density isn't great enough, the procedure can be
done over to increase the dye image. If the density is too great, rinse
the negative in stop bath (dilute acetic acid) and the stain intensity
will be reduced with acid treatment (increased with base).

>
> > ..I was able to boost negatives via bleaching and re-developing in Pyro
> > for Cyanotype and Ziatype. The starting negative had too little density
> > for a good Cyanotype
>

Cor Breukel

http://ruly70.medfac.leidenuniv.nl/~cor/cor.html
"The Infrared Gallery"
http://ruly70.medfac.leidenuniv.nl/~cor/ir-gallery.html



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