[Alt-photo] Re: DAS

[Keith Gerling]

Thanks!  That is very helpful.  So 3% is a saturated solution?  Since I'm
typically sloppy, chemically-challenged and don't even own a scale, my
routine with dichromates has always been to just use a saturated solution,
dumping in dichromate and water as needed.  Would this work with DAS, maybe
diluting it as needed?  In other words, does a mixed solution keep?


On Fri, Apr 12, 2013 at 3:33 PM, Kees Brandenburg
<workshops at polychrome.nl>wrote:

> Hi Keith,
>
> I started using powdered casein, 4 gram in 25 ml cold water. After a 1
> hour soak I am adding 1 gr ammonium carbonate in a little (1 or 2 ml)
> water. Warming this 'au bain marie'  and stirring until most of the bubbles
> are gone results in a fairly thick casein paste.
> I started testing with a 1:1 mix of this casein preparation with a
> saturated 3% DAS solution and lampblack watercolor pigment. After some
> tests I started cutting down the DAS concentration and am using a 2%
> solution now. Lower concentrations might work too. With this mix I can
> print negatives with a lot larger density range than I am used to with gum.
> My first tests were dissappointing because of a too low negative contrast
> and a too high sensitizer concentration. Printing times are (much) shorter
> than with dichromates.
>
> Kees
>
> On 12 apr. 2013, at 21:29, Keith Gerling <keith.gerling at gmail.com> wrote:
>
> > I purchased some to use with casein.  I haven't tried it yet, but I'm
> happy
> > to hear you've had good success with it.  Would you mind sharing your
> > casein procedure?
> >
> > Keith
> >
> >
> > On Fri, Apr 12, 2013 at 1:37 PM, Kees Brandenburg
> > <workshops at polychrome.nl>wrote:
> >
> >> I was wondering if there are people on the list who participated in the
> >> DAS group buy that was organized some time ago.
> >> DAS is the acronym for 4,4'-Diazidostilbene-2,2'-disulfonic acid,
> disodium
> >> salt, tetrahydrate and is a non- or less toxic replacement for
> dichromates
> >> in carbon printing. I am using it for some years now and am quiet happy
> >> with it. Most handy is the non existing dark effect. Carbon tissue can
> be
> >> made presensitized. This speeds up printing a lot.
> >>
> >> Recently I also tested it with casein and found out that it works
> >> extremely well!  I am looking forward hearing other people's experience
> >> with this powder!
> >>
> >> Kees
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