Page 1 of 21 12311 ... LastLast
Results 1 to 10 of 203

Thread: Obsidian Aqua, catechol staining developer

  1. #1

    Join Date
    Sep 2003
    Location
    Seattle, Washington
    Posts
    2,920

    Obsidian Aqua, catechol staining developer

    I'd like to introduce a new developer I've been testing for some time, and will continue to test and use. I call it Obsidian Aqua, for its scalpel-sharpness and water base.

    Obsidian Aqua is very closely related to Hypercat II, but takes advantage of some of the opportunities an aqueous solution provides for economy, without sacrificing keeping prperties. The main reason for using propylene glycol in Hypercat II is to extend its keeping properties, but this comes at at some cost. PG is not locally available in many places, and is expensive to ship, and adds considerable expense to the developer. In Obsidian Aqua I've tried to maximize keeping properties while minimizing expense, including shipping costs, by utilizing locally available ingredients where possible, including the use of distilled water as the solvent. Like Hypercat II, OA uses catechol as its sole developing agent, but OA is preserved by metabisulfite in the stock solution, instead of ascorbic acid, and retains carbonate as the accelerator. OA can be made up in sodium or potassium metabisulfites and carbonates, depending on availability.

    To maximize the keeping properties, the stock solution is highly concentrated. This allows for a higher ratio of catechol to metabisulfite, and a lower ratio of metabisulfite to water compared to other catechol staining developers, which simultaneously improves stain formation and keeping properties. A working solution of catechol/carbonate developer with appropriate carbonate content requires practically no preservative. The preservative is primarily required for the stock solution.

    To make a working solution, the OA stock solution is dissolved into a solution of 6.66% carbonate, and how this is managed will depend on the carbonate used, and the preferences of the photographer. A 66.6% solution of potassium carbonate can be made by dissolving 666g of potassium carbonate to make 1 liter of stock solution, or 6.66g of either carbonate can be dissolved in a liter of water to make a working solution, or any number of other possibilities. The important thing is that the working developer contains 6.66g of carbonate/ liter.

    Obsidian Aqua

    Distilled water 700ml
    Metabisulfite (sodium or potassium) 20g
    Catechol 250g
    Distilled water to 1 liter

    Dilute 1:500 with 6.66% carbonate solution (sodium or potassium, depending on which metabisulfite is used in the OA stock solution). 1 liter of Obsidian Aqua makes 500 liters of working solution.

    Develop TMY-2 12:00 @ 70F with *geometric agitation sequence.

    Obsidian Aqua produces negatives of unsurpassed sharpness, excellent gradation, very fine grain, and full film speed. OA can be used with rotary processing, but with some loss of film speed. I hope this developer will be more convenient for my friends overseas, who often need to order supplies from outside their own countries. I highly recommend Artcraft Chemicals for catechol. Artcraft offers 250g of catechol, which wouldn't require any weighing of the chemical to make up the stock solution; just mix the entire amount to make 1 liter. The metabisulfite is not critical, and could be measured with measuring spoons if no scale is available. 1 level teaspoon of metabisulfite weighs approximately 6.5g, so 3 tsp/ liter is close enough.

    Obsidian Aqua stock solution should keep very well. Though I have no stock solution older than 6 months, I expect it to last at least a year in a partially full glass bottle. Time will tell.

    I hope this formula is useful for anyone desiring the sharpest possible negatives with the best overall Image Quality, at the least possible expense, wherever one might live.


    * The notion of a geometric agitation sequence was recently suggested to me, and I've been using it with good results. My method is as follows:

    I use a count up timer, and begin by agitation continuously for 1 minute. Then I reset the timer and agitate for 10 seconds, according to the following progression (in minutes): 2, 4, 8, 16, 32, etc.

    A geometric agitation sequence seems appropriate for this kind of very dilute developer, and my results bear this out.

  2. #2

    Join Date
    Dec 2001
    Location
    San Joaquin Valley, California
    Posts
    6,531

    Re: Obsidian Aqua, catechol staining developer

    PG does a splendid job of keeping Prince Albert pipe tobacco fresh! Such a good job that the Prince moved out of his can and into a "Luxury Pouch."
    This new developer sounds very interesting---I may have to give it a try. Thanks for sharing!
    I steal time at 1/125th of a second, so I don't consider my photography to be Fine Art as much as it is petty larceny.

  3. #3

    Join Date
    Sep 2003
    Location
    Seattle, Washington
    Posts
    2,920

    Re: Obsidian Aqua, catechol staining developer

    The working solution is essentially the same as Hypercat II, which I've been using for quite a while, and some other photographers, too. Incredibly sharp! Good luck, and please don't hesitate to contact me with any questions or comments.

  4. #4
    Drew Wiley
    Join Date
    Sep 2008
    Location
    SF Bay area, CA
    Posts
    6,879

    Re: Obsidian Aqua, catechol staining developer

    If it's as good as the name you picked for it, I'll have to try it! Maybe you should be
    in marketing!

  5. #5

    Join Date
    Apr 2009
    Posts
    342

    Re: Obsidian Aqua, catechol staining developer

    Quote Originally Posted by Drew Wiley View Post
    If it's as good as the name you picked for it, I'll have to try it! Maybe you should be
    in marketing!
    Oh, man I can see it now....

    Cue to OA Man, the rugged individual surveying his Bad Lands domain from the hilltop in profile against the far horizon, no shirt and ample sixpak, displaying the results of lugging a Deardorf through the hills for years.

    He turns and takes a few steps towards the camera his flinty gaze burning through the f64 lens while the Badlands background fades to SHARP black and white. Slowly stroking his salt and pepper beard, he touches his Stetson in a gently greeting and says;

    "Use Obsidian Aqua, for Acutance you can depend on."

    /gth

  6. #6
    MIke Sherck's Avatar
    Join Date
    Mar 2002
    Location
    Elkhart, IN
    Posts
    1,227

    Re: Obsidian Aqua, catechol staining developer

    Quote Originally Posted by gth View Post
    Oh, man I can see it now....

    Cue to OA Man, the rugged individual surveying his Bad Lands domain from the hilltop in profile against the far horizon, no shirt and ample sixpak, displaying the results of lugging a Deardorf through the hills for years.

    He turns and takes a few steps towards the camera his flinty gaze burning through the f64 lens while the Badlands background fades to SHARP black and white. Slowly stroking his salt and pepper beard, he touches his Stetson in a gently greeting and says;

    "Use Obsidian Aqua, for Acutance you can depend on."

    /gth
    Cue the soundtrack music from "The Good, The Bad, and The Ugly".

    Mike
    Politically, aerodynamically, and fashionably incorrect.

  7. #7

    Join Date
    Sep 2003
    Location
    Seattle, Washington
    Posts
    2,920

    Re: Obsidian Aqua, catechol staining developer

    Quote Originally Posted by gth View Post
    Oh, man I can see it now....

    Cue to OA Man, the rugged individual surveying his Bad Lands domain from the hilltop in profile against the far horizon, no shirt and ample sixpak, displaying the results of lugging a Deardorf through the hills for years.

    He turns and takes a few steps towards the camera his flinty gaze burning through the f64 lens while the Badlands background fades to SHARP black and white. Slowly stroking his salt and pepper beard, he touches his Stetson in a gently greeting and says;

    "Use Obsidian Aqua, for Acutance you can depend on."

    /gth
    I love it!

  8. #8
    8x20 8x10 6x9 John Jarosz's Avatar
    Join Date
    May 2006
    Location
    Fairfax Iowa
    Posts
    457

    Re: Obsidian Aqua, catechol staining developer

    Is the stain similar to Pyrocat and other staining developers? i.e, proportional to silver density?

    Thanks

    John

  9. #9

    Join Date
    Sep 2003
    Location
    New Berlin, Wi
    Posts
    1,252

    Re: Obsidian Aqua, catechol staining developer

    Excellent, I have 20 pounds of potassium carbonate lingering on the shelf and have all the other chems..I'll try this. Jay, how much loss of speed with rotary agitation? Could be a useful tool too..Evan Clarke

  10. #10

    Join Date
    Sep 2003
    Location
    Seattle, Washington
    Posts
    2,920

    Re: Obsidian Aqua, catechol staining developer

    John,

    Yes, the stain is proportional, and the same brown-ish color as other catechol staining developers.

    Evan,

    In my tests, OA produces a speed increase of about 1/3-1/2 stop over box speed with Low Frequency Agitation, and rotary processing costs up to a full stop, or about 1/2-2/3 stop under box speed. Except for the speed loss, OA is excellent for rotary processing, producing no fog or general stain, and very even development with no streaking or mottling, but it really shines with Low Frequency Agitation, where it produces maximum acutance and compensating effects. But, if you can live with the speed loss, I think you'll be very happy with your results from rotary processing, too.

    I'll try to post an example of OA with rotary processing.

Similar Threads

  1. Glycin and staining developers
    By Jarin Blaschke in forum Darkroom: Film, Processing & Printing
    Replies: 15
    Last Post: 3-Aug-2012, 04:50
  2. pyro developer, but which?
    By sergiob in forum Darkroom: Film, Processing & Printing
    Replies: 206
    Last Post: 25-May-2012, 18:06
  3. Ideal Developer for Film to be Scanned
    By Jay DeFehr in forum Darkroom: Film, Processing & Printing
    Replies: 34
    Last Post: 12-Apr-2010, 05:09
  4. Which staining developer?
    By Leonard Metcalf in forum Darkroom: Film, Processing & Printing
    Replies: 21
    Last Post: 21-Oct-2007, 08:13
  5. Old Formulas : Film
    By Paul Fitzgerald in forum Darkroom: Film, Processing & Printing
    Replies: 6
    Last Post: 19-Mar-2005, 20:31

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •