From: Sandy King (firstname.lastname@example.org)
Date: 12/07/02-03:14:36 PM Z
I have a further concern about VDB that results from the processing
of very large prints. When I make such prints my practice is to make
them in the darkroom but for reasons of space wash them outside. The
washing usually takes place in the afternoons when the sun is still
up, in the shade on the deck. Even after processing that includes
toning, two separate fixing baths, and a final bath of 1% sodium
sulfite, VDB prints will develop very noticeable fogging when the
wash takes place outside, even in very low light. I am wondering if
in spite of all of the processing care there are not still some
soluble salts left in the paper? If so this suggests the need for a
very long wash, even if using hypo clear or sodium sulfite clearing
baths. I thought at first that the fogging might be due to something
else in the paper other than silver salts but the fogging only takes
place in the areas that have been brushed with the sensitizer.
BTW, the fogging does not take place with kallitype processed
following the same procedures.
>Good work, Richard, you've proved an important point. It hadn't even
>occurred to me that it needed proving, but if there's a rumour circulating
>that VDBs/kallis dont need fixing, well... it has to be squashed.
>When you toned, you said that the density produced got less with longer
>washing times. Washing removes soluble compounds, not insoluble (unless a
>few "loose" crystals on the surface), so the difference is due to the
>removal of soluble silver salts. The question, therefore, is whether any
>insoluble salts are also present, which would need to be fixed out - if
>toning still had an effect after 10 minutes' washing, whatever got toned
>can't have been very soluble, so I'd say the answer is "Yes" (and that
>further washing would not reduce the toned density any further!). Insoluble
>salt does form in VDB and can be seen as a precipitate in old solutions, but
>are tiny, insoluble particles also suspended in the liquid?
>My guess is that insoluble silver salts are not present in the sensitiser,
>but form on contact with buffered papers and that, maybe, you'd get away
>with just washing VDBs on unbuffered paper. But maybe not, too, because
>some organic, insoluble silver salts might form with the paper matter
>itself. One way to test that would be to repeat your test on a synthetic
>paper - I had some once, but it was such horrible stuff I threw it away. I
>tried coating VDB on plastic, but couldn't. I can't do a conclusive test,
>therefore, but do have an unbuffered paper here, Atlantis Silversafe, and
>some Arches Aquarelle which I know is heavily buffered with carbonate.
>OK, the results are in (some 2 hours later): I used a thiourea sepia toner
>(10 g thiourea + 10 g sod. hydroxide in 1 litre), and toning produced bad
>staining on both papers when they had been washed 10 minutes but not fixed.
>Staining was a little less on the unbuffered. This suggests to me that
>buffered paper is one reason why fixing is needed, but not the most
>important one. The formation of insoluble organic silver compounds on the
>paper is another explanation, but it strikes me that there could be another:
>residual iron, forming ferrous sulphide on toning. I seem to remember
>hearing/reading somewhere that hypo gets rid of iron, but can't remember
>where or say if it's true.
>P.S. The scale was several steps shorter with the unbuffered paper (equals
>a more contrasty print), though whether this is actually due to its lack of
>buffering I couldn't say, though I suspect it is. And something
>interesting: when a fixed and (fairly briefly) washed VDB was put in sepia
>toner (as above), the shadows darkened quite quickly and the image tone
>gradually became cooler. No bleach was used before the toner.
>From: email@example.com [mailto:firstname.lastname@example.org]
>Sent: 05 December 2002 09:45
>Subject: VDB test results - part 1
>Last night I ran some tests on the the need for fixing with
>VDB. For the impatient, just read the conclusion below.
>I used 3 types of paper (Rising Stonehenge, Canson Cartridge,
>Canson Colorline). The reason for choosing three was to get a
>spread of clearing behaviour. Stonehenge clears easily, the cartridge
>clears more slowly, and the Colorline shows a slight stain even after
>extended washing. I took two pieces of each and coated about
>2/3 of the surface of each. The uncoated section was to help
>judge any staining later in the test. These were dried with cool
>fan blown air.
>One set of three papers was washed for a total of ten minutes.
>First for two minutes with continuous aggitation, then in
>two changes of water for 4 minutes each with intermittent
>aggitation. All water used for the above was tap water with
>a pinch of citric acid added to ensure it was close to neutral
>pH. The second set of three papers were washed for 2 minutes
>with continuous aggitation. This was in water which had been
>filtered through both mechanical and carbon filters.
>After the washing I examined the paper (while still wet).
>As expected both Stonehenge had no visible stain. The cartridge
>after 10 min wash was clean, but after 2 min wash showed a very slight
>amount of stain. The Colorline showed slight stain in both samples.
>I then placed the paper into Agfa New Viradon (polysulphide) toner.
>All papers darkened very quickly. I continued to tone for 10 minutes,
>then washed and air dried the paper.
>All papers showed significant brown colouration on the coated part.
>This was about the same as "mid tone" on a VBD. Interestingly
>the colour is close to that of a normal VBD, unlike the yellow-brown
>that resulted from trying to tone a fully processed VDB print.
>The papers which had been washed for 10 minutes were slightly
>less dark than those washed for 2 minutes. This suggests the
>silver content could be removed by washing alone, but I suspect
>it would take hours to acheive this. The degree of staining was
>different between the three papers, but in all cases was significant.
>VDB prints contain signifiacnt amounts of silver in unexposed regions
>after washing. This is true regardless if any visual staining is
>present or not. VBD prints need to be fixed. I suspect the minimum
>fixing time will probably vary with paper etc.
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