Obsidian Aqua, catechol staining developer

[Jay DeFehr]

Jay,

Could you give a starting point for Ilford PanF, expose box speed I guess, but process for how long at what temperature?

Thanks,

Cor

Hi Cor,

OA and PF+ is one of my favorite combinations. A good starting point is:

OA 1:500, 70F, 8:00, agitate first 30 seconds, and then ten seconds/ minute.

The above should provide a point of departure for your own testing.

John,

I'm happy to share my work with other photographers, and I hope you find something useful in it.

[Cor]

Thanks Jay!

I'll report back (although it will be 35mm.....)), I just have to wait for sufficient light outside right now,

Best,

Cor

[Jay DeFehr]

Hi Cor,

If you shoot in flat light, you might want to increase development a little. I think you'll like this combination.

[Andrew O'Neill]

Anyone knows where you get catechol in Canada?

/gth

You can get catechol from Nymoc in Toronto. Email John Burrows: nymoc@bellnet.ca

[Dan Henderson]

I finally got caught up on some other pressing projects and had time to shoot a scene on which to test Obsidian Aqua developer, and offer the following comments:

1. The "A" portion of the developer was easy to mix, metabisulfite and catechol in distilled water. Rather than make a stock "B" solution, I added enough sodium sulfite to water to make a 6.66% working solution into which I added the 1:500 dilution of developer.

2. Following Jay's recommendation I developed 4x5 FP4+ for 9 minutes at 70 F. I agitated for the first 30 seconds, then 10 seconds every 2 minutes.

3. I got a nice, easily printable negative. Good contrast, same stain as I am accustomed to with Pyrocat.

4. To attempt to ascertain any difference in sharpness, I made an enlargement of a section of the negative with lots of detail at the highest magnification my setup will allow (actually as large as my anatomy will allow; with my eye to the focus finder I could just barely reach up to the focusing knob.) It is roughly equivalent to a 20x24" enlargement.

5. I compared this enlargement to an identical enlargement of another negative of the same film, exposed at the same time, but developed in Pyrocat HD, using semi-stand agitation. Using a strong magnifier, I "think" the O.A. enlargement is nominally sharper. I intended to scan and post the enlargements but they are so close that I am sure any differences would not survive the scanning and uploading process. At any rate, I feel comfortable stating that the O.A. enlargement is no worse than equally as sharp as the Pyrocat enlargement, even with more aggresive agitation.

6. As sharp as this negative is, I wonder if it could be improved with a less aggressive agitation routine, such as 30 seconds initial agitation followed by 10 seconds of agitation at the 1/4, 1/2 and 3/4 points, or even 1/3 and 2/3. I intend to explore this idea in the near future.

Thanks again to Jay for providing this developer, and for his generosity in sharing it here.

[MDR]

Thank you Jay for providing once again an alternative developer. Have to try it as soon as I can get all the ingredients. Btw have you noticed that your stated amount of carbonate is the number of the beast 666 maybe that's why your developer works so well :-)

Dominik

[gth]

Jay,

1. What is the shelf life of the Catechol compound by itself? Reason I ask because in Canada it needs to be shipped as a dangerous compound so I might as well get a fair amount while I am at it. In other words several years worth.

2. How much diluted solution is needed to develop a specific amount of film - as in film area per liter? Normailized to How many rolls 35 or 120 per liter or how many 4x5 sheets per liter etc. This estimate to be taken conservatively.... i.e assuming I would be fairly frivolous with its use - one shot type....

3. Also... has anyone used OA on X-ray film emulsions?

/gth

[mat4226]

3. Also... has anyone used OA on X-ray film emulsions?

I've used OA with quite a few sheets of X-ray film now, and all I have to say is I'm in love! With that interval agitation Jay talks about on the first page, 1,2,4,8, etc., I'm able to shoot Green Latitude X-ray film @ ASA 320. This is, of course, considering I'm not stripping the emulsion, scanning and contact printing works fine. Here's a link to all the images I've already shot with OA as the developer, including 4 infrared shots as well (also great with OA!).

http://www.flickr.com/photos/mat4226/tags/oa/

[UlbabraB]

3. Also... has anyone used OA on X-ray film emulsions?
/gth

I plan to test it soon with Kodak T-Mat Green Xray film, Mat Marrash (IIRC he is a LFF member too) already did it, check his flickr stream: http://flic.kr/p/bzD9iU

[Max Hao]

Thanks for the correction, Claudio. Your pH calculation looks about right, too.

So, is it 0.666% sodium carbonate solution or 6.66%? How many grams of sodium carbonate in 1000ml water? Thanks.