rurmonas@senet.com.au
Date: 12/05/02-03:44:50 AM Z
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.
CONCLUSION
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.
Richard
--- Richard Urmonas rurmonas@senet.com.au ------------------------------------------------- This mail sent through SE Net Webmail http://webmail.senet.com.au
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