Peter Marshall (petermarshall@cix.co.uk)
Mon, 22 Mar 1999 22:47 +0000 (GMT)
> At 10:47 PM 3/21/99 -0500, Judy wrote:
> >I never had the patience to mix all the chemicals you needed with the
> >Rochelle-salt developers, they really took huge amounts, at least the
> >formulas I had. In fact I couldn't get them all into solution & then
> they
> >didn't last very long.
>
>
> I believe the old formulas called for sodium borate decahydrate which
> has a molecular weight of 381.37 where the (dry) fused version has a
> molecular weight of 201.22. None of the historical formulas specify
> which hydrate to use but I strongly suspect that it is the decahydrate.
> I think most people will end up today with the dry version. Thus if the
> old formula calls for 500 grams you would use only 260 gms of the dry
> stuff. This accounts for why you have all that sludge in your tray when
> you try to mix the old formulas.
>
>
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>
I believe it is safe to assume than any alkaline developer used in the
kallitype process is likely to result (eventually) in the fading of the
print. I don't know if Mike Ware has ever pronounced on the relative
stability of VDB (know in the past as both 'kallitype' and
'water-developing kallitype' but seldom as Van-Dyke print), but I
certainly have speculated that the water developed version seems more
likely to be stable.
Peter Marshall
On Fixing Shadows and elsewhere:
http://www.people.virginia.edu/~ds8s
Family Pictures, German Indications, London demonstrations &
The Buildings of London etc: http://www.spelthorne.ac.uk/pm/
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