Group Purchase of Azide/Diazo Sensitizer - replacement for dichromate in carbon, etc.
A group buy is being organized to purchase an azide sensitizer (erroneously referred to diazo as well) for use in the carbon process.
We've been discussing this in depth on this thread (last several pages), but I thought I'd post a specific thread to get anybody who may have missed the other.
In case you're not familiar, azide and diazo sensitizers are non-toxic alternatives to potassium & ammonium dichromate. They are not carcinogens, are not environmental pollutants and have no shipping restrictions.
Moreover, they don't have a dark reaction and thus can be incorporated into carbon tissues from the outset and can be stored for extended periods of time. UltraStable Color Carbon Tissues were made with this very same sensitizer, and tissues that are 15+ years old still expose and etch within very acceptable limits.
I believe this stuff can revolutionize the carbon process. It will work on all protein-hardening based colloids (caesin, gelatin, etc.) but may not work for gum. Please refer to the experts on this point...
Anyways, if you're interested please PM me, post here or email me at my APUG username @ yahoo.com. This group buy represents a very significant savings over other suppliers and is the same stock that Tod Gangler uses to make his color carbon prints.
We're looking at somewhere between $180 to $200/kilogram, plus shipping. International should be OK.
FYI, they are used at a smaller percentage than the dichromates; somewhere around 0.6% if incorporated into the "glop".
Still working out the details, but so far the response has been great!
Just wanted to drop a quick update; things are still progressing.
Thanks for sittin' tight!
Chris, is the purchases list fixed yet?
Or can one still get in?
Its works well on gum too (DASGum Process?).
Originally Posted by holmburgers
Hi Michael, no the list is definitely not fixed. If you are interested, I will get you on there. Just send me an email so I have something "official". The same goes for anyone else. Nothing is set in stone until the order is made, and there will be a lot of notice before that happens.
And there you have it, good for gum too!
The latest news I can give is that I'm still waiting to hear back from Tod Gangler about the samples he is testing. Like I said in the beginning, this will take a few months, if not more. All systems are still go though.
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Early report from Tod is that the DAS sensitizer is 'perfect' - an exact match of what he has been using (they are probably from the same batch). In any event, he'll be sending Chris densitometer measurements and etc in a few days.
BTW: APUG'er Rob Shaffer and SJSU Alternative Media teacher Hedwig Heerschop will be presenting the results of their DAS-Gum experiments at the November 17th meeting of the Historic Photo Processes Forum http://www.santacruzmah.org/event/hi...esses-forum-3/.
I've sent you a PM; Did you receive my e-mail?
I've just placed the big buy announcement on the classifieds.
This is the home stretch; please get the word out about this sensitizer and encourage your friends to try it! It's time to get enough people to start working with DAS; catalyzing a lasting and positive change in the carbon printing process.
Originally Posted by CMB
After reading this I did my DASgum test again by mixing a regular 14 baumÚ gum pigment mix 1:1 with a 3% DAS solution. Normaly I mix this 1:1 with a 10% potassiumdichromate. With several exposure times longer and shorter than my regular 4 minutes I never could make the gum harden and hold the pigment. Gum is different than other collo´ds being a polysaccharide. As I have understood the hardening in the gum process is of the complex forming kind as in prote´n based collo´ds the DAS hardening is of the free radical type. But correct me if I'm wrong.
For the gummist there is hope too. I am currently testing DAS with several synthetic collo´ds and one of these looks very promising. It's even cutting down exposure times in a dramatic way. Only how to call this new approach...
I will post about this and other non-toxic pigment collo´d methods on zerochrome.org in the near future. So maybe I should coin zerochrome for the newborn.
I looked this up in Kosar's Light-Sensitive Systems and found on page 331 of my 1965 copy, in the section about aromatic azides, a reference to a (Fr. ?) patent (886,716/1942) by Kalle A.G.
In this reference Kosar states that with gum arabic, dichromates can be replaced by DAS. I wasn't able to track this patent yet, but I have the impression Kosar did not check this himself. As far as I know Kalle A.G. was a German company. It was also active in the production of light sensitive papers, mostly for diazotype, which are not the same as aromatic azides. Kosar states in a note (75) that the patent is french, which is somewhat strange for a german company.