WHich Dichromates am I looking for at art chemicals?

Discussion in 'Alternative Processes' started by mark, Jan 28, 2013.

  1. mark

    mark Member

    Messages:
    5,264
    Joined:
    Nov 13, 2003
    I am comparing prices on potassium dichromate/ammonium dichromate between photo formulary and art chemicals, to start carbon printing. Photo formulary is easy they have one of each. Art chemicals not easy becasue they have like several pages of each. If I was going to compare apples to apples what do I look at?
     
  2. anikin

    anikin Subscriber

    Messages:
    891
    Joined:
    Nov 16, 2009
    Location:
    Capital of O
    Shooter:
    Multi Format
    For carbon printing you are better off getting DAS sensitizer. Holmburgers is organizing a purchase right now.
    Hopefully, you are not too late: http://www.apug.org/forums/forum379...azing-dichromate-alternative.html#post1447181

    It is much more environmentally friendly and way better than dichromate since you can make your tissues ahead of time and have them ready for exposure at any time - unlike dichromate, DAS sensitized tissue does not deteriorate in storage.

    Eugene.
     
  3. Vaughn

    Vaughn Subscriber

    Messages:
    5,307
    Joined:
    Dec 13, 2006
    Location:
    Humboldt Co.
    Shooter:
    8x10 Format
    Both (dichromates and DAS) have their issues. I believe the clearing bath for DAS is more toxic than that of the dichromates.

    But as far as the dichromates, either will do, but I use the Ammonium dichromate(AD) -- which is stronger acting gram-to-gram compared to Potassium dichromate(PD). That is because Ammonium is lighter than Potassium...thus at the same weight of the two compounds, one gets more dichromate using, let's say, one gram of AD than one gram of PD. But once corrected for the difference, they act pretty much t he same.

    Vaughn
     
  4. mark

    mark Member

    Messages:
    5,264
    Joined:
    Nov 13, 2003
    My goal is to do everything with water no special clearing bath, so to begin with I am going with the dichromate. the DAS idea means more chemicals to order and takes the simple out. So is it the reagent version, the purified version, or the GR ACS version of Ammonium Dichromate.
     
  5. jorj

    jorj Member

    Messages:
    43
    Joined:
    May 2, 2011
    Location:
    Philadelphia
    Shooter:
    Medium Format
    Whichever's cheapest. :smile:
     
  6. Vaughn

    Vaughn Subscriber

    Messages:
    5,307
    Joined:
    Dec 13, 2006
    Location:
    Humboldt Co.
    Shooter:
    8x10 Format
    I'll go along with this. One would probably see no difference between the lowest and highest grades. Consistancy would be more important (using the same type/source).

    If one is using the double transfer method, no clearing bath is needed. With the single transfer method, a clearing bath is recommended as some dichromate can be trapped between the gelatin and the final support during transfer. I use Potassium alum right after the cooling bath (after the transfer). It has been found that any dichromate left behind slowly hardens the gelatin and increases its brittleness over a lot of time (your descendents will have to deal with it -- not you. But no problem, really, if one keeps the prints flat.

    Vaughn.
     
    Last edited by a moderator: Jan 28, 2013
  7. CMB

    CMB Member

    Messages:
    98
    Joined:
    Mar 17, 2011
    Location:
    Santa Cruz,
    Shooter:
    Multi Format
    To be clear, do you mean more toxic than dichromates or more toxic than dichromate clearing baths?

    Charles
     
  8. anikin

    anikin Subscriber

    Messages:
    891
    Joined:
    Nov 16, 2009
    Location:
    Capital of O
    Shooter:
    Multi Format
    I suspect Vaughn meant clearing bath. Pretty much anything is more toxic than warm water :smile:

    The mix of table salt, sodium sulfite and a bit of potassium permanganate (typically used as drinking water disinfectant) is not terribly toxic, but it's still more chemicals than plain water :D
    But it is more stuff to buy than just the dichromate, so OP's point makes sense.
     
  9. mark

    mark Member

    Messages:
    5,264
    Joined:
    Nov 13, 2003
    Hold the phone. I have not read or watched anything that mentions a clearing bath for dichromates, and I have been reading a lot. I missed the DAS buy anyway.
     
  10. Vaughn

    Vaughn Subscriber

    Messages:
    5,307
    Joined:
    Dec 13, 2006
    Location:
    Humboldt Co.
    Shooter:
    8x10 Format
    From the potassium permanganate msds:
    Just don't eat more than 9 grams, and also your wife can go off the pill...

    Potassium alum -- used in pickleing/canning foods, in deorderants -- but this is not to say that all the chemicals we put in our foods or under our arms are actually safe.


    The latter.

    Mark -- Most carbon printers of old used the double transfer method -- to get the image back to its original orientation (and hide any relief). Since in double transfer exposes both sides of the tissue to water, just about all the dichromate is washed off...thus you may not read much about clearing needs in the older literature.

    Another way to clear single transfer is using sodium or potassium metabisulfite. But because this greatly softens the gelatin, it can cause frilling and bubbling of the image. It is recommended that one allows the print to dry for a day or two, which hardens the gelatin -- then clear it in the metabisulfite. I use the Potassium alum right after the cooling bath, followed by the wash. Fits better into my work-flow.
     
    Last edited by a moderator: Jan 29, 2013
  11. anikin

    anikin Subscriber

    Messages:
    891
    Joined:
    Nov 16, 2009
    Location:
    Capital of O
    Shooter:
    Multi Format
    I'm sorry I mentioned toxicity in my original post. It was not my intention at all, merely to inform the original poster of the ongoing DAS purchase if he wants it. Next time I should be more careful on my choice of words. Most of us here deal with chemicals on a regular basis and understand the real and imaginary dangers. Let's drop this subject before someone else jumps in - there is no new information to discuss that we don't already know. Peace?

    Eugene.
     
  12. Vaughn

    Vaughn Subscriber

    Messages:
    5,307
    Joined:
    Dec 13, 2006
    Location:
    Humboldt Co.
    Shooter:
    8x10 Format
    Peace? There was never conflict, at least from my perspective. And information is always new to those who have yet to hear it.

    I was not just answering your post, but expanding mine.

    vaughn
     
  13. Andrew O'Neill

    Andrew O'Neill Subscriber

    Messages:
    1,164
    Joined:
    Jan 16, 2004
    Location:
    Coquitlam, B
    Shooter:
    8x10 Format
    Thanks for the tip, Vaughn.
     
  14. Vaughn

    Vaughn Subscriber

    Messages:
    5,307
    Joined:
    Dec 13, 2006
    Location:
    Humboldt Co.
    Shooter:
    8x10 Format
    The Potassium alum also hardens the gelatin, but it is not an immediate effect. In fact it is used (or was used) in pickling to harden the cell walls to keep the fruit (and cucumbers) from being mushy. Why it is used in underarm deorderants, I do not know.