[Alt-photo] Dichromate Poisoning
jimbobnola at cox.net
Mon Oct 30 16:17:50 UTC 2017
Hi Richard and Larry,
Cerium iii Chloride hardens gelatin moderately, and Cerium iv Ammonium Nitrate hardens gelatin strongly. I reconfirmed that yesterday by coating a 5% solution of each on a strip of B&S carbon tissue, then soaking it in warm water. The cerium iii was hardened down to the base. The cerium iv was very hard, like when you over expose a dichromate carbon tissue. I tried Cerium iv Ammonium Sulfate dihydrate, complexed with Ammonium Citrate, dibasic (1:2 by wt) with a CAS concentration of 5% and AC 10% solution on a strip of carbon tissue. I then exposed it to UV with a strip of black paper down the middle. I was surprised to find that the unexposed area was hardened, and the exposed area dissolved away. ? possible to do a direct positive process. I will work on that later. I did develop a type of carbon process by coating paper sized with waxy corn starch, coating with CAN in very dilute nitiric acid, drying, exposing the paper through a positive to UV, then soaking the C tissue in 2% oxalic acid, mating, developing as usual.
The most relevent sources I used for GB alternates were the following: Google these: Polymerization system using Ceric salts, Photoinitiation cerium iii sulfite, Eosin Y photopolymer. These processes are free radical polymerization. I have avoided Acrylic Acid as it is toxic and carcinogenic. I have used as binding polymers: gelatin, fish glue, PVP, PVAl, methyl cellulose, and gum Arabic. I have used as monomers and crosslinkers: polyethylene diacrylate, 400; N-vinyl pyrrolidone; N,N-methylenebisacrylamide, and diacetone acrylamide. My best results are with PVP K60, NVP, and MBA. I am planning to post a print soon and you can judge if it is worthwhile. Note that the Eosin Y is sensitive to green light, not UV, so you can use a bright LED light or sunlight.
Jim Patterson, New Orleans
On October 27, 2017 at 4:15 PM Richard Sullivan <sullivan8486 at gmail.com> wrote:
>From CameraCraft 1929 pg 593
The OCR scan is a bit weird!
The Carbon Process
Dr. E. J. Tritton recently read before
the Royal Photographic Society (G. B.)
an exhaustive and rather technical paper
on methods of increasing the printing
speed of bichromated gelatine, inasmuch
as this includes the printing of carbon
tissue and the carbon process still holds
an important place in professional portrait photography, its practical application will interest carbon workers.
"If a small quantity of a cerium salt
for example cerous chloride is added
to the usual dichromate bath, the speed
of the resulting carbon tissue is considerably increased, while the subsequent
development, and other operations remain
exactly as usual. A suitable formula for
a sensitizing bath is:
Pot. dichromate pure cryst 2% parts
Cerous chloride 10% sol 2 parts
Water 100' parts
"It is most important to note that only
pure dichromate should be used, and no
ammonia must be added tc it.
"The disadvantage of this process is that
it does not keep well. A much better
method is to sensitize the tissue in plain
dichromate, e. g., the above formula with
the cerous chloride omitted, and then to
give only one-third of the exposure that
would be required under normal circumstances.
"For mounting, instead of soaking the
tissue the normal way in water, a 2%%
solution of cerous chloride is used. When
the tissue is limp to the correct extent in
this solution it is mounted on the soaked
transfer paper in the normal way, left between blotting boards 15 minutes, and then
developed in hot water. A full strength
image is then attained without any other
variations in the process. The time of
soaking the tissue in the cerous chloride
solution has practically no inlluence on
the density or gradation Of tin- image obtained, and neither is the exact concentration of tin- Quid of great importance, but
with both very weak and very strong solutions, such as 1% to 4'/t, there is a tendency to flatness. The cerous chloride solution can be used over and over again,
and also a used solution can be stored and
then used again, despite the fact that it
gathers dichromate from the sensitive tissue, after a time however the resulting
prints are found to be slightly flatter.
"Obviously by employing this procedure
the normal keeping qualities of the tissue
are retained, but it is equally obvious that
any tint or fog that may be on stale tissue
will be just as much intensified as the
exposed image. Hence only fresh tissue
should be employed."
On Fri, Oct 27, 2017 at 1:19 PM, Larry Ogrodnek via Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org mailto:alt-photo-process-list at lists.altphotolist.org > wrote:
> Hi Jim,
> I'm interested to learn more about these alternative sensitizers -- do you
> have any text/links/reference you could send on their use?
> On Thu, Oct 26, 2017 at 10:42 AM, Jim Patterson via Alt-photo-process-list <
> alt-photo-process-list at lists.altphotolist.org mailto:alt-photo-process-list at lists.altphotolist.org > wrote:
> > Hi All,
> > Being an occupational physician I am aware of the risks of Chromium VI.
> > On the certification exams they always have questions on chrome holes,
> > perforated nasal septum, and nasopharyngeal and sinus cancer.
> > I have been a student of Chris and she preaches safe handling and personal
> > protective equipment.
> > In the past 2 yrs I have been experimenting with alternate Sensitizers and
> > colloids. The most promising at the moment are Cerium IV Ammonium Sulfate
> > and Eosin Y.
> > Both of these harden gum Arabic, gelatin, fish glue, cellulose gum, PVP
> > and others. I am not saying they are better than GB, but are alternatives.
> > Jim Patterson, New Orleans
> > Sent from my iPhone
> > > On Oct 26, 2017, at 2:12 AM, Charles Berger via Alt-photo-process-list <
> > alt-photo-process-list at lists.altphotolist.org mailto:alt-photo-process-list at lists.altphotolist.org > wrote:
> > >
> > > My post was prompted by the declaration of a highly regarded arts
> > > educator/author that if/when dichromate was restricted here, as it is in
> > > the EU, she had a sufficient supply for her and her students to continue
> > > using it indefinitely.
> > >
> > > This cavalier attitude towards the use of dichromate for the sake of
> > > photographic printmaking is ill advised as it implies that the dangers
> > are
> > > not to be taken seriously.
> > >
> > > Responses ranged (with a few exceptions) from the abusive (and idiotic)
> > > advise not to “lick the top of Cherry wood table” to a non-sequitur
> > > description of the installation of seat belts in a 1956 Oldsmobile.
> > >
> > > The point I was making is that there is little discussion of dichromate
> > > poisoning and a lack of detailed information (beyond “wear gloves”) on
> > its
> > > safe use in the current literature on alternative photo processes.
> > Perhaps
> > > Marton was correct when he wrote about “The Dichromate Disease” in The
> > *Photo
> > > Oleograph Process*(1900) that “Rich living and alcoholic stimulants, seem
> > > to foster this peculiar ailment”, and thus all we need to do is avoid
> > such
> > > behaviors to safely work with dichromate.
> > >
> > > Why are so many of you upset about discussing this? And why do you feel
> > > compelled to defend this lack of concern and to dismiss any in-depth
> > > information on the subject as “scare tactics?”
> > >
> > > Full disclosure: I have recently been exploring with Chris the creation
> > of
> > > a book (or series of books) describing non-toxic alternatives to historic
> > > photographic printmaking. Her statement caught me completely by
> > surprise. I
> > > am confident that Chris is truly concerned with the health and safety of
> > us
> > > all, but this dismissive attitude is unfortunate.
> > >
> > > Charles
> > > _______________________________________________
> > > Alt-photo-process-list |http://altphotolist.org
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