[alt-photo] Re: and a warning...

[Loris Medici]

Hi Francis,

Take care to add Solution C (silver nitrate) to A+B very slowly (almost drop
by drop) while stirring vigorously. It may lead to less precipitate. OTOH, I
always get a precipitate with VDB sensitizer. It's probably related to my
particular ammonium iron(III) citrate (AFC) batch, since I know someone else
who doesn't get any precipitate and they use someone else's AFC. My AFC is
from B&S, the other AFC which doesn't precipitate is from Sigma-Aldrich...
Who's AFC do you use?

Anyway, just let the solution ripen a couple of days (shaking it a couple of
times each day, e.g. once in the morning and once in the evening), then
filter it to a new container. I use coffee filters and I filter twice. There
will be almost no remaining precipitate; 1-2mm at the bottom of the 250ml
bottle at max! Draw the necessary amnt. of sensitizer with a syringe or
plastic pipette w/o disturbing the bottle and you're done.

Maybe it's the solids that are giving you troubles. OTOH, any iron present
in your water / brush / paper ... (you got it!) will definitely cause
staining, therefore pay attention to that also...

Regards,
Loris.


-----Original Message-----
From: alt-photo-process-list-bounces at lists.altphotolist.org On Behalf Of
Francis Schanberger
Sent: Tuesday, February 02, 2010 3:12 PM
To: The alternative photographic processes mailing list
Subject: [alt-photo] Re: and a warning...

...

Last month I made a about 150cc of vandyke brown according to the recipe in
Chris James book and I got a lot of precipitate that is still reluctant to
do any substantial settling. I have only been able to draw off about 40 cc
of solution to print from. (I am going to make some new vdb today).

With the light ground vdb prints I have been working on, one image in
particular seems to display a random stain (different places, same negative,
each time I print it). It doesn't bleach away with potassium ferricyanide.

...