From: Liam Lawless (liam.lawless@blueyonder.co.uk)
Date: 02/16/02-07:19:24 PM Z
Sandy,
I've done a quick experiment and think the VDB scale can be shortened by 3
or 4 steps, without increasing printing times or diminishing D-max (though
results appear to be somewhat variable on different papers). To compare the
result with straight VDB, have a look at
http://www.artphoto.pwp.blueyonder.co.uk/vdb.htm/
Instead of 9 g of f.a. citrate in the "A" solution, I used 3 g f.a. citrate
plus 6 g ferric citrate. This is a very fine brown powder that looks like
powdered rust, and is not very soluble; a sludge forms at the bottom of the
mixing vessel. Increasing the tartaric acid to about 4 g in "B" seems to
help dissolve it, but some still remains. It can be filtered out, or just
take care not to shake it up before using the sensitiser. The "C" solution
still uses 3.8 g silver nitrate; the modified sensitiser has a paler colour
but coating and processing are as normal.
Why does it work? I'm not sure, but recent postings about the *new* Pt/Pd
contrast agent got me thinking. I didn't read them all, but Chapman Jones
(Photography of To-Day, 1913) says:
"... we find attempts to formulate a method for [platinum] as far back as
1845. These early experiments failed because the compound of platinum with
the maximum amount of chlorine was used, so that even if some of the
chlorine was removed directly or indirectly by the agency of light, the
soluble compound with less chlorine in it was produced, and the amount of
metal deposited was very slight, if any."
Mike Ware confirmed that this is true, in an e-conversation. It seems to
me, therefore, that Na2PtCl6 probably effects a proportional reduction that
appears visually greater in the highlights. Maybe there's an analogous iron
or silver compound to do the same thing in VDB? If so, I don't know what it
is, but I remembered that I'd used ferric citrate in blue toning experiments
some years ago. As far as I recall, it produced much less colour than
ferric amm. citrate, so maybe it would fit the bill. Apparently, it does.
Ferric citrate is described as "Light Sensitive" on the bottle, and I can
spare 50 g or so if you need it. Let me know where to send it.
Liam
-----Original Message-----
From: Sandy King [mailto:sanking@clemson.edu]
Sent: 16 February 2002 03:47
To: alt-photo-process-l@sask.usask.ca
Subject: Re: VDB formulas
Judy Seigel wrote:
>
>There are I think 3 [VDB formulas in P-F #1], one that didn't work AT ALL,
>one that sort of worked but wasn't very good, and the regular classic VDB
>we know. That last is what I refer to -- but in some sources (which I do
>not bring to mind), the part about "contrast control" with dichromate came
>with it.
The last is the one that I have also been using.
>
>My folder on VDB is on a high shelf, & to get it down disturbs a lot of
>asbestos particles, & other fallout from WTC (not to mention the usual
>dust mites and mold spores), but *I believe* I exposed to the max, that is
>to the point that the bottom steps blocked up. I therefore assumed that
>the cliff at the other end was intrinsic, not to be overcome by more
>exposure (although Sandy says didn't find that !!!).
Right. Nothing that I did actually increased contrast.
First, I added potassium dichromate to the developer as James
recommends, at the same strength, at less strength,and at more
strength. Nothing.
Second, I added potassium dichromate to the sensitizer prior to
coating the paper. This resulted in a huge loss of effective printing
speed, but no change in contrast. That is, the test wedge with and
without the addition of potassium dichromate had the same number of
steps from Dmax to Dmin.
All of my solutions were fresh and mixed with distilled water?
>-But if you want to increase contrast in the negative, I found that
>chromium intensifier followed by selenium toner 1:3 gives the biggest
>increase in neg density, also red color which is another filter, and quite
>a jumpl A very brief Farmer's reducer before the intensifier can weaken
>highlights for even more contrast.
I have used this method before and know that it works. Unfortunately,
in this instance my negatives already have a DR of around 1.6,
perfect for my carbon printing, and I have no desire to further
increase their contrast.
Too bad that so much unverified BS has been lavished on the naive by
persons who did not take the time to verify for themselves procedures
which they claim to work. I find fault with James (and others) for
this, in spite of many other fine things about his book which I would
praise, and even though he has probably been effectively immunized
from criticism by his praise of all the esteemed and venerable in the
world of alt photography, including - and in the same sentence - Judy
Seigel, Dick Sullivan and Mike Ware.
But I am still looking for an effective way to control contrast with
the classic VDB formula.
Sandy King
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