Re: question about VDB

FWIW, I mixed some up the other day using a magnetic stirrer, and got no
precipitate at all. Previously, whenever I mixed it up using just a stirring
paddle, I always got some precipitate.

Clay

Quoting TERRYAKING@aol.com:

>
> In a message dated 12/4/06 4:49:19 pm, dstevenbryant@mindspring.com writes:
>
>
> >
> > ? Many, but not all of the formulas call for dissolving all of each
> > chemical, separately, in a third of the water. Thus, 27 grams in 100 ml
> etc
> > and finally mixing them. I use 33 ml lots to make a total of 100 ml at
> the
> > end.
> >
> > I needed to get from my sick bed back to the studio before I tried to
> > consider the question. As you suggest, the amounts should be
> >
> > 9 g of FAC in 33 ml of purified water
> > 1.5 g of tartaric acid in 33 ml and
> > 3.8 g of silver nitrate in 33 ml.
> >
> > Given that I have never had problems with precipitate I wondered what could
>
> > be going wrong when other people did.
> >
> > I am not suggesting that any of these apply to other people's practice, but
>
> > things that can go wrong include:
> >
> > contamination of containers with other chemicals or tap water for which one
>
> > should always wash the containers in purified water and then dry them to
> > reduce the risk
> >
> > contamination of tools,brushes and rods from even a single grain of another
>
> > chemical
> >
> > getting the sums wrong
> >
> > confusion of grains for grams somewhere in the calculation
> >
> > using tap water instead of distilled or purified ( silver nitrate solutions
>
> > will go white when contaminated with tap water as the chlorine in the water
>
> > will change silver nitrate to silver chloride).
> >
> > That this list can go on and on is an indication of how important it is to
>
> > be very very careful even with such a simple process.
> > >
> > While all of what you say is true, I think the fact that Charles, Loris,
> > and myself have all observed the same results of precipitate when adding
> the
> > final volume of silver nitrate solution (part C) to the mixed parts A and B
> is
> > an indication that this is a common occurrence in fact an expected one
> based
> > on our experience.
> >
> > Perhaps some of our experienced VDB printers can comment one way or
> > another.
> >
> >
>
> Maybe my procedure has something to do with why I do not get precipitate.
> Maybe this is 'old hat' but I stir slowly with a glass rod when adding
> the
> silver nitrate, pouring the silver nitrate gently down the rod as I stir.
> Randall and I did this when we made our first kallitypes (VDBs) in the
> seventies.
> i mentioned this to Randall yesterday, he said that he has got over alt
> processes.
>
> Terry
>
>
>
> Terry King FRPS
>
> RPS Historical Group (Chairman)
>
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