Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
Jay DeFehr
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.
Thanks, I rate 400 TMY at 320 when metering and Pyrocat MC is one of my developer choices, I always make at least two duplicate sheets. I'll make this tomorrow and compare this weekend..Thanks, Evan
Re: Obsidian Aqua, catechol staining developer
Anyone knows where you get catechol in Canada?
/gth
Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
evan clarke
Thanks, I rate 400 TMY at 320 when metering and Pyrocat MC is one of my developer choices, I always make at least two duplicate sheets. I'll make this tomorrow and compare this weekend..Thanks, Evan
Great! I look forward to your impressions.
Re: Obsidian Aqua, catechol staining developer
Dang, Jay...you are about to drag me back to pyro...
Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
Vaughn
Dang, Jay...you are about to drag me back to pyro...
Vaughn, I think it's an ideal developer for your work, and your development method (trays, right?).
Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
gth
Anyone knows where you get catechol in Canada?
/gth
Trying again!
Re: Obsidian Aqua, catechol staining developer
Re: Obsidian Aqua, catechol staining developer
Jay, a little mistake.
"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. " You need a carbonate dilution with 6,66g in each liter (1000 ml), and this means 0,666% not 6,66%. This solution have a pH of 11,14.
I suppose when you mix with the catechol and metabisulfite of part A, the pH lower to around 11.
Claudio Szarfsztejn
Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
ClaudioSz
Jay, a little mistake.
"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. " You need a carbonate dilution with 6,66g in each liter (1000 ml), and this means 0,666% not 6,66%. This solution have a pH of 11,14.
I suppose when you mix with the catechol and metabisulfite of part A, the pH lower to around 11.
Claudio Szarfsztejn
Thanks for the correction, Claudio. Your pH calculation looks about right, too.
Re: Obsidian Aqua, catechol staining developer
Jay,
Your mention of "produces no fog or general stain" drives me to ask... would this developer be a better choice than others when using older films from the freezer that may have a growing density of base + fog as they age (i.e. Super-XX)?
Chris