Group Purchase of Azide/Diazo Sensitizer - replacement for dichromate in carbon, etc.

Discussion in 'Alternative Processes' started by holmburgers, Sep 18, 2012.

  1. holmburgers

    holmburgers Member

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    Hi all,

    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!

    Thanks all,

    Chris
     
  2. holmburgers

    holmburgers Member

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    Just wanted to drop a quick update; things are still progressing.

    Thanks for sittin' tight!
     
  3. michaelbsc

    michaelbsc Member

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    Chris, is the purchases list fixed yet?

    Or can one still get in?

    MB
     
  4. CMB

    CMB Member

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    Its works well on gum too (DASGum Process?).

    Charles
     
  5. holmburgers

    holmburgers Member

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    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.

    Cheers guys,

    Chris
     
  6. CMB

    CMB Member

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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/historic-photo-processes-forum-3/.

    Charles
     
  7. Paolo M.

    Paolo M. Member

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    Hi Chris,
    I've sent you a PM; Did you receive my e-mail?

    Paolo
     
  8. holmburgers

    holmburgers Member

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  9. keesbran

    keesbran Member

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    Hi Charles,

    After reading this I did my DASgum test again by mixing a regular 14 baumé 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 colloïds being a polysaccharide. As I have understood the hardening in the gum process is of the complex forming kind as in proteïn based colloïds 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 colloïds 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 colloïd methods on zerochrome.org in the near future. So maybe I should coin zerochrome for the newborn.

    regards,

    kees
     
  10. keesbran

    keesbran Member

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    DASgum

    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.

    -k
     
  11. CMB

    CMB Member

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    It seems that Kosar (and myself) are guilty of the same thing - advocating a process/procedure that we had not independently verified. Your findings that DAS does not sufficiently harden gum to hold pigment has been confirmed by fellow APUGer and Gummist Rob Shaffer who has been conducting DAS/Gum tests and reported his findings in the November meeting of the Historic Photo Processes Forum. The good news is that he found that DAS works well with casein and Rob will soon be posting his findings here. I am most interested to learn of the results of your experiments using DAS with synthetic colloids.


    Charles
     
  12. keesbran

    keesbran Member

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    I found several other patents today that reference to the (indeed) french Kalle patent, but I am still not sure what the original patent says about gum. Anyway for me and Rob it doesn't work apparently. I also tested DAS with casein, and indeed it works. I'll post my findings with the synthetic colloïds (PVA, PVP) soon. At this moment I find exposure times in the range of 15 seconds (!) with one colloïd/DAS mix. Tonal scale is rather short. Synthetic colloids come in various grades, each with their own specifications. Molecule length, degree of hydrolization etc. That makes it difficult to understand all variables. I have been looking through piles of patents with references to aromatic azides, DAS and colloïds. Very interesting. Kosars' book is still a great standard though.

    -kees
     
  13. sehrgut

    sehrgut Member

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    Is this group buy still going on? I saw on the other thread that the drop-dead date is January 27th . . . I'd love to get in on this with 100g or so to play with.
     
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  15. keesbran

    keesbran Member

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    See this post
     
  16. sehrgut

    sehrgut Member

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    Thanks!
     
  17. Hologram

    Hologram Member

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    I just had a look at FR 886,716. Gum is not mentioned there. The colloids listed in that patent are: gelatin, methyl cellulose and PVA/methyl cellulose.
     
  18. keesbran

    keesbran Member

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    That's what I concluded from all the references too. Did you find it online somewhere?

    -k
     
  19. Hologram

    Hologram Member

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    Yes, here: http://depatisnet.dpma.de
     
  20. Mark Fisher

    Mark Fisher Subscriber

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    I'm sure you folks know this, but I'd feel guilt if I didn't mention it....

    If this stuff is sodium azide, it isn't exactly harmless....it is highly toxic and dangerous. We use it at work and it is really nasty stuff. Most azides, I believe, are pretty nasty. I'm sure it can be handled safely, but spend some time looking up the precautions.
     
  21. keesbran

    keesbran Member

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    It is not. We are talking about: 4,4'-DIAZIDOSTILBENE-2,2'-DISULFONIC ACID DISODIUM SALT or CAS 2718-90-3, with this molecular formula. It's the same as the 'Hardener #3' used in the Ultrastable pigment papers.
     
  22. sehrgut

    sehrgut Member

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    Simple azide salts are indeed pretty nasty, but aromatic azides are different animals. Kinda like the difference between simple cyanide salts (like sodium cyanide) and complex cyanides (like potassium ferricyanide). Most importantly, the organic azides are not explosive like sodium azide is.
     
  23. Mark Fisher

    Mark Fisher Subscriber

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    Fair enough. I'm just a simple mechanical engineer that hangs out with a few chemists and biologists. I know just enough to say silly things.....
     
  24. holmburgers

    holmburgers Member

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    This is the final day ya'll! If you're interested, please send me an email so I can get your order in.

    I do however, hope to buy a little bit extra that will be available after this purchase. The price however, might be slightly higher.
     
  25. sehrgut

    sehrgut Member

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    Ah! Almost forgot! Just sent the money your way . . .
     
  26. Tonyrjr

    Tonyrjr Member

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    Is the group purchase for the sensitizer still open? What is a reasonable amount to order, 100 Gm? I'm not yet a carbon printer but would like to do some. let me know by email if I can still join.
    THanks,
    Tony Rustako
    ajr1000@att.net