RE: VDB

On Thu, 13 Oct 2005, Loris Medici wrote:

> I'm sure I can't get even close to 1.2 with one coat VDB (subjective
> comment: didn't measure, don't have a densitometer). Your 1.5 is very close
> to semi-matte RC paper max. density (which is around 1.6 IIRC)... If I were
> getting such density I'd never bother with double coating. I have Stonehenge
> paper sitting somewhere, will try it for VDB when I will have time...

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?

Are all chemicals known to be good?

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?

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 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.)

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.)

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

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

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

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.)

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...

cheers,

Judy
Received on Sat Oct 15 23:12:34 2005