Pyro redevelopment


Liam Lawless (lawless@vignette.freeserve.co.uk)
Sat, 23 Jan 1999 23:51:22 +0000


Hi everyone,

Thanks to all who've contacted me on this subject. Maybe I've spoken a
little prematurely, but when it happened I was excited by what I expected to
be a routine test, and felt the need to tell someone! I understand that we
all have our own way of doing things, so please someone tell me to shut up
if I'm starting to bore you, but I don't think the subject's exhausted just
yet

So you're sceptical about my claimed density increase on redeveloping in
PMK? I put this down to the way the densitometer reads the stain colour
(since, remember, the before and after densities themselves look about the
same), but I've now put it to the test. I measured a well-defined area of
an APH negative, and the results were 2.44 before staining, 3.17 after
bleaching, PMK for 15 minutes, a fix and then drying. After giving a
further 2 minutes in the used developer (as per Hutchings' instructions) the
same area measured 3.21. Bleach was 28g pot. ferri. + 24g pot. bromide in 1
litre.

I have no idea why my results are at variance with Sandy's, especially since
the bleach he used is essentially a chromiun intensifier with bromide added.
But, a question: does development really continue for as long as 20 minutes,
or is it only staining that increases after a certain point? As stated
above, my APH was redeveloped 15 minutes, and to be sure that it was fully
developed after this time I fixed only half the sheet at first. No
difference between fixed and unfixed halves.

The colour of the stain on APH is reddish, similar to a selenium-toned
chlorobromide print. Many people appear t be using Tri-X for alt. quite
happily, but my comments were based on my stained Agfa step wedge which I
thought was stained about the same as Tri-X, but in view of everyone's
comments I've had a closer look at it and indeed find it has a higher
stain-to-silver ratio at any given density. The staining of my wedge is
also quite different to APH, so I now need to try printing from APH.

Nevertheless, I know that unstained pyro negs can produce the same image
quality on silver-gelatin as stained negs, and I see no reason why this
shouldn't also be the case with UV printing. Perhaps there are good reasons
for so doing: lower fog, for example, or more consistent image quality with
different film stocks? Perhaps not, but hopefully we'll find out.

If anyone has the time, I'd very much like to know if they can confirm my
finding that bleaching ordinarily developed APH (or other lith) and
redeveloping in PMK increases densities. Or should I get a new
densitometer?

Thanks,

Liam



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