RE: Shelf Life of Van Dyke Sensitizer

[Keith Gerling <kgerling@ameritech.net>]

Judy
>
>> The Farber instructions are as follows:
>>
>>1) add 10 grams Ferric Ammonium Citrate to 10 ml distilled water
>> 2) to that, add a solution of 1.5 grams Tartaric Acid and 35 ml distilled
>>water
>>3) to that, add a solution of 4 grams Silver Nitrate and 35 ml distilled
>> water

>In any place, that's NOT a good way to mix VDB... Each chemical should be
>mixed separately in its own water, then A & B combined, and C (the silver
>nitrate) added

That's what I was trying to express.  My apology to the list and to Farber
if I didn't get it make it clear.  In any event, the solutions were mixed
separately and added together.


>If you're not getting good D-max, you may be...

>heat drying (lowers D-max, on some papers blows it right out)

>not coating properly (ie, not wetting paper enough)

>using stupid paper

>adding gelatin size to paper

>adding some cockamamie ingredient, like gum arabic, to emulsion

>having bad chemicals

>not using distilled for emulsion

>fixing too long (2 minutes absolute MAXIMUM, after which fixer bleaches)

>or fixer too strong, try 26 g am thio to (is it a litre? this from memory)
>water

>or possibly not washing ENOUGH in the water before putting in fixer. Do a
>time test... Sometimes with thicker paper this first wash has to be longer
>than 5 minutes...

Nope on all of the above, except possibly the last one.  I've used the
pre-mixed Van Dyke sensitizer from Bostick and Sullivan, who definitely know
what they are doing, and got the exact same results as with my own mixtures:
weak shadows.  Really, though, what kind of DMAX can one expect when using
Van Dyke?  How does is compare with Kallitype?  My kallitypes provide dense,
rich blacks that are indistinguishable from platinum.  I'm happy. actually,
to stick with kallitypes, and only mixed up this Van Dyke sensitizer because
I had the chemicals on hand and was lacking the Ferric Oxalate for the
kallitype.  I'm assuming that the same fixer, paper, etc. that produces a
good kallitype can make a good Van Dyke.  But now I am curious as to how a
really good Van Dyke compares to a really good kallitype, and am interested
in hearing from anybody who has had success with both processes.



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