Obsidian Aqua, catechol staining developer

[catalinajack]

[QUOTE=Regular Rod;1059754]I don't think dry Catechol goes off if sealed in a jar. In fact I believe that is one of the characteristics that Jay took into consideration when he was devising OA to last indefinitely.

Did you use Sodium Metabisulphite in your solution A? I think we are supposed to use Sodium Carbonate in Solution B if we use Sodium Metabisulphite and if we use Potassium Metabisulphite in solution A we should use Potassium Carbonate in solution B

Here's how I make up mine after Jay explained to me how I could save on the quantities of distilled water needed:

OBSIDIAN AQUA

Solution A
Distilled Water - 300 ml
Sodium Metabisulphite - 8 g
Catechol - 100 g
Distilled Water to make - 400 ml

Solution B (Concentrate)
Distilled Water - 4 litres
Sodium Carbonate Anhydrous - 1 kilo
Distilled Water to make - 5 litres

Working Solution
Solution A - 1 ml
Solution B - 12.5 ml
Tap Water to make - 500 ml

Try 12 minutes @ 20 degrees C semi-stand to start with. That is 60 seconds gentle agitation followed by 10 seconds gentle agitation every two minutes. A pre-soak in water at 20 degrees C seems to ensure even development quite nicely.


I tried 12 minutes at 20C, agitating every two minutes. Tried twice and got only totally clear negatives, NOTHING! I checked and double-checked the formulae and the mix I used to develop. No mistakes. I used 2.6ml of Solution A, 32.5ml of Solution B added to 1300ml of water. What am I doing wrong. I got the chemicals fresh from Artcraft. Am using sodium rather than potassium.

[Jan Pedersen]

Sounds like you have exactly the same problem as I did.
In the end I made the OA with Potassium Metabisulphite and Potassium Carbonate and can make good looking negatives now. TMY an exception, those negatives are still much to thin but Fuji Acros and Plus-X (Small format) looks good.

Did you get all chemicals fresh or just some of them?

[catalinajack]

Got them all fresh from Artcraft. I will try the potassium varieties but I wonder why you are still getting thin negatives with TMY. For me, I am certain it's the developer cuz I took a baseline shot and developed it using Xtol. My film? Delta 100. And, of course, all of my other shots have been taken under constant lighting and the same stop and shutter speed. It's not exposure variances for certain. It seems the developer using the sodiums are wiping everything from the film. Perhaps the times should be much shorter.

[Jan Pedersen]

At this time we must conclude that it is consistently inconsistent and to much of a risk to use on important images.

[Regular Rod]

It is a puzzle. I have experienced nothing but good results from OBSIDIAN AQUA since I started using it. Today I developed three films all at the same 1:500 mix, all at 20 deg. C and all at 12 minutes semi-stand. The films were HP5 Plus 120, HP5 Plus 35mm and ADOX CHS 25 Art 120. My best pal uses ILFORD's Delta films including Delta 100 and gets great results from OBSIDIAN AQUA too.



I just cannot imagine what is causing this problem for you...

RR

[onnect17]

The oxidation of the developer is directly linked to the agitation which depends of the speed and design of the tanks in the Jobos. Also, the amount and/or concentration of developer solution needs to be considered, so allow me to suggest using 2:2:100 instead of the regular 1:1:100 and start your tests on the 5 min mark.

I'm talking about Pyrocat-HD, forgot to mention.

[onnect17]

At this time we must conclude that it is consistently inconsistent and to much of a risk to use on important images.

I wonder if the issue is the sodium carbonate vs potasium carbonate. Part B of Pyrocat-HD can be used for the tests.

Anybody with good results using sodium carbonate?

[Regular Rod]

Mine is all made with Sodium Metabisulphite and the Sodium Carbonate (anhydrous).

RR

[mikoyan]

me too.

[onnect17]

Good, so it's not the sodium carbonate. How about agitation, who's using 1:1:500 with the jobo?