From: Sandy King (sanking@clemson.edu)
Date: 09/24/03-11:24:55 AM Z
Altering the ratio of the three chemicals will note give you more
contrast. You can try it but you will just be wasting your time.
There is a method which involves altering the classic solution by
mixing ferric ammonium citrate with ferric citrate. This method was
described in the last edition of Post-Factory Photography, and you
could also find it by searching the list archives. As I recall I
posted the message sometimes in the spring of last year.
The lack of contrast could be caused be the paper, as others have
suggested. There is no doubt but that paper matters a lot with VDB.
Sizing paper with gelatin or starch is not necessary with VDB,
however, and in my opinion will likely cause additional problems.
The most likely reason for the low contrast is the negative. Most
people don't realize that the classic VDB mix requires a negative
with a *very* high density range to print with good contrast. By that
I mean a DR of log 2.25 and even higher, which is much higher than
you can get with OHP material with most printers. You can test the
premise by just printing a plain sheet of the OHOP material, using
test strips of different times to make sure you are getting enough
exposure.
Sandy King
>
>I am working on a series of van-dyke brown prints. I have used the
>standard mix of ferric ammonium citrate, tartaric acid, and silver
>nitrate, in the usual recommended quantities, mixed 1:1:1 , fixing
>it for a minute in very dilute sodium thiosulphate.
>
>I have tried various exposures, but at darkest, it is giving me a
>dull mid brown. I want to achieve that really rich blackish brown,
>any idea if there's a way to get this with the chemicals I am
>using...can I change the ratios of the mix to get a darker tone?
>
>Jane.
>
>
>
>
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