RE: question about VDB

I got that precipitate all the times (using B&W FAC). My observations
are same as yours; it starts to precipitate at the end and suddenly... I
leave the precipitate intact during the ripening period (1 - 2 days),
shaking the bottle occasionally (3-4 times a day) and then filter the
sludge before first usage (I do this one time; it never makes new
precipitate). The batches I've made that way were consistent. I had
similar sludge / precipitate when mixing Argyrotype so I'm inclined to
think that it's something related to my FAC. Since it doesn't show any
bad effect, I don't see that as a big problem. Just a quirk that I have
to deal one time for each batch.

Regards,
Loris.

-----Original Message-----
From: ryberg [mailto:cryberg@comcast.net]
Sent: 10 Nisan 2006 Pazartesi 00:20
To: alt-photo-process-l@usask.ca
Subject: question about VDB

   I'm using the formula found in James (well, actually his formula
divided
by 3). He calls for three 100 ml solutions--27 g FAC, 4.5 g tartaric
acid,
12 g silver nitrate. I have, on four different occasions, mixed VDB
sensitize. In the first three I got a LOT of precipitate which I
filtered
out. In all cases the remainder worked well and seemed consistent from
batch to batch. Since none of my sources mention a precipitate, much
less a
very heavy one, I thought I was doing something wrong and made one
change
each successive time. I switched to distilled water--no change. I
added
the silver nitrate solution very slowly--no change except I realized the

precipitate occurred quickly toward the end of the addition. On batch
number four I attempted to stop at the first sign of precipitate and,
sure
enough got only a little, though I had not added the full amount of
silver
nitrate solution. This sensitize seems to act much like the first
three.
    All of my chemicals are fresh and from well respected suppliers.
    So, do any of you get such a precipice and if so, what do you do
besides
filter?
Charles Portland OR
Received on Mon Apr 10 03:59:31 2006