Re: question about VDB

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)

www.hands-on-pictures.com/

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Received on Wed Apr 12 10:38:48 2006