On 13 Aug 2021, at 22:35, `Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
Good on you! I was going to add just a little. There is some information,
not a lot, in the old literature on reversal processing. The process really
has to be tailored to the specific material although the fundamentals are the
same. Many reversal first developers have a small amount of halide solvent in
them, sometimes thiosulfate but often thiocyanate. The idea is to eliminate
the slight fogging that causes a haze on the reversed pictures. Also, the
second developer is usually a very active developer, like Dektol. The grain
is evidently established by the first developer so using an active reversal
developer does not result in large grain. Also, the reversal can be done
using a solution of sodium sulfide, essentially the same stuff used for
redeveloping two step sepia toner. Of course, the images are sepia colored.
Kodak has formulas for reversal development of printing paper in some of
its old processing and chemical booklets.
Reversal processing of 8 and 16mm motion picture film was very common but I
don't remember if I ever saw published formulas for the process.
Another note: film designed for reversal has an excess of silver halide in
it to make sure there is enough to produce full density of the final image.
Motion picture film for projection must have rather high density and contrast
to avoid looking washed out. Probably the same for B&W slides.
I would invite reporting on any practical experience list members have with
reversal, either film or paper, and, to be clear, on any experiments done. It
is a fascinating process and, like monobath, not widely practiced.
On 8/13/2021 12:55 PM, Laurence Cuffe (Redacted sender cuffe for DMARC) wrote:
Dear All,
Just after I posted this query, my computer started acting oddly, so I ended
up doing a full copy onto an old disk drive and a further copy of my
pictures library onto another disk drive. they were old mechanical drives,
so this was not a fast process, hence my delay in responding.
Many thanks to the following:
Luis Miguel Castañeda,
Terry Hosinger,
Karstwalker,
Titrisol,
and Nicholas O. Lindane for their very prompt responses to my queries about
Gainers formulas and reversal processing.
It was all very useful.
Luis, Thanks for the upvote for Patrick Gainer, from what I have found on
the web he seemed to be a very likeable, knowledgeable and generous man.
Terry, That was exactly the information I was looking for on reversal. The
use of Sodium Bisulfate 25g/l as a substitute for sulphuric Acid, 10ccConc/l.
Karstwalker Thankyou for the same information, and the link.
Titrisol, Thanks for another upvote for Gainer, and the link:
https://web.archive.org/web/20180225015603/http://silent1.home.netcom.com/Photography/Dilutions%20and%20Times.html
<https://web.archive.org/web/20180225015603/http:/silent1.home.netcom.com/Photography/Dilutions%20and%20Times.html>
to Donald Quall’s DonaldQualls collection of recipe’s some good stuff there,
which will require close reading and some exploration in the darkroom.
Finally Nicholas. Over here in Ireland, Autoparts stores, do not routinely
sell Sulphuric acid. My local Halfords stopped doing it in 2018, as owning
Sulphuric acid in the UK now requires an explosives precursor licence. The
Irish stores are subsidiaries of the UK firm. I can source it as drain
cleaner, but I’m a bit leary of doing that, because I don’t know what else
is in there, hence my query. I think with the help of everyone who
contributed here, I’m now good to go. thanks again all,
All the best
Laurence Cuffe
On 12 Aug 2021, at 20:40, Nicholas O. Lindan <nolindan@xxxxxxxxxxxxx
<mailto:nolindan@xxxxxxxxxxxxx>> wrote:
Sulfuric/battery acid should be available from the autoparts store. You
can get sulfuric acid at the hardware store as acid drain cleaner but it
has additives to keep if from attacking metal pipes. Or, you can order it
from Photographers' Formulary or ebay. The battery acid stuff is 35%
(IIRC) and less nasty than the ~90-98% 'concentrated' form.
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
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