RE: VDB

hi judy and loris,
thank you for these suggestions.

> I'm puzzled by the reports about insufficient VDB density... also
> emulsion ruination... I've used single coat VDB emulsion aged nearly 2
> years, plated out in the bottle, full of black precipitate, etc. etc.
> without problems and with good d-max.
>
> Wondering about:
>
> Is it possible a weaker formula circulates? What formula are folks using?

I use the same classic formula

> Are all chemicals known to be good?

98% or more.
 
> Do you trust your scale? (That's a relatively small amount of silver
> nitrate, so truth in weighing matters.) Is the silver nitrate still
> white?

yes

> And the water: We had a problem when the silver precipitated out as soon
> as it was added to the water, BEFORE combining with the other solutions.
> The hardware store had sold us tap water in a "distilled" water container.
> (On a hunch I brought it to the chem dep't which confirmed.)

I use a very pure water. it is produced by the biochemical laboratory where
my girlfriend works. they produce two differents kind of water and I use the
purest one. is not distilled but filtered using a special machine.

> (I note that I was mixing the silver solution in a babyfood jar with a
> metal cap... When it precipitated right out, I thought it was the cap. I
> suppose the cap didn't help, but it was the water.)

I use plastic cap.

> Are you sure your container is light tight? Not all colored plastic is.
> (I kept the brown glass bottle, with black plastic cap, in a dark closet
> when not in use.)

I do exactly the same.

> Are you using a *dedicated* applicator -- say, foam brush that doesn't go
> into anything else?

yes, a chinese brush only for vdb.

> Does the paper lie on a *clean* surface for coating? (If stroke extends
> over the edge & onto a dirty surface, it picks up stuff.)

yes

> Are you gelatin sizing? VDB does NOT like gelatin size.

no, I use arche platine as it came out from its box.

> And fixer -- I found that two minutes in a plain fix of (percent I'd have
> to look up, but much weaker than standard fix) was the longest and
> strongest you could use without bleaching. (I probably have it somewhere,
> probably in P-F, but it made an enormous difference.)

I fix in this way:
2' in a solution of 1ml acetic acid (98%) per litre of water (tap water)
2' in plain tap water
1' in 2% hypo solution
1' in a fresh 2% hypo solution
5' in running water
2' in 1% sodium sulfite solution
2' in running water
20' of final wash
 
> Also, I mention what maybe most folks know, but the books seem to have
> wrong -- The first rinse, in plain water, before fixing, should not be
> just "until the water runs clear." A student did a variables test and
> found a much brighter deeper print with a 5 minute rinse before fixing.
>
> Heat drying the emulsion kills D-max, but storage before exposure and
> before development can also cut densitity. And probably more variables I'm
> not thinking of now...

I never heat to dry.
I sensitize with 0.7ml of solution for a 13x18cm surface. i put my brush in
distilled water and then I shake it two times. in this way it is just a
little bit moist. after the first coat I put the paper in the darkness, I
wait 10', I sensitize in the same manner, and I wait 40'. then I expose.
I don't mesure the density, but I obtain very dark blacks.

the only things I don't like is the precipitate that forms in the bottle. I
adds solution C really slowly (30' to add 33ml of c solution to 66 of a+b).
after more or less 25ml the solution start to precipitate. I wait two days
and then I filter all this green precipitate. the solution is light green,
and if I don't filter it I have I grainy and inconsistent result. I don't
like the precipitate cause I say to my self that I'm loosing some salt that
could be used to increase dmax...
ciao
f

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Received on Mon Oct 17 02:16:01 2005