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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.
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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!
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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.
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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!
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
Drew Wiley
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
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
gth
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
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
gth
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
:D I love it!
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Re: Obsidian Aqua, catechol staining developer
Is the stain similar to Pyrocat and other staining developers? i.e, proportional to silver density?
Thanks
John
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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
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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.
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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
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Re: Obsidian Aqua, catechol staining developer
Anyone knows where you get catechol in Canada?
/gth
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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.
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Re: Obsidian Aqua, catechol staining developer
Dang, Jay...you are about to drag me back to pyro...
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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?).
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
gth
Anyone knows where you get catechol in Canada?
/gth
Trying again!
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Re: Obsidian Aqua, catechol staining developer
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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
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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.
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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
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Re: Obsidian Aqua, catechol staining developer
Hi Chris,
Yes, I think so, but there's some question as to whether a staining developer of any kind is the best choice for films with a lot of base fog. I suppose a staining developer can still provide a larger density range than a non-staining developer, important if one is printing in a long scale process, but staining the fog will definitely increase printing times, so it's a judgement call. But yes, if you are decided to use a staining developer, one that produces the minimum general stain is the best choice.
Catechol itself is quite resistant to fogging, which contributes to general stain. In catechol developers that produce fog/general stain, it is almost always the secondary developing agents responsible. This is why a catechol developer that also includes phenidone requires a restrainer. Phenidone, and even metol produce fog in a pH environment appropriate for a catechol developer, and provide no benefit to justify this fault. I don't think phenidone or metol are superadditive with catechol, and perhaps not even additive. If you compare developing times for standard dilutions of Obsidian Aqua and Pyrocat HD, for example, you'll see what I mean. Even though OA contains no phenidone, and uses a lower concentration of carbonate, development times for OA are typically shorter than development times for Pyrocat HD at comparable dilutions. How can this be? Well, I don't know, exactly. There's an awful lot of reactions taking place in a Pyrocat HD working solution that are not present in OA, and some must have a braking effect on development. The same is true for Tanol Speed, which contains both catechol, and pyrogallol, along with two other developing agents, and yet development times are longer than with OA, and fog/general stain are higher, too.
In my opinion, catechol developers are not improved by the addition of secondary/tertiary etc. developing agents, and all the other ingredients added to mediate their effects. Simply balancing the concentrations and ratios of catechol, preservative and alkali is all that is required to make a developer that does everything we want one to do, and nothing we want it not to do. All the rest is obfuscation and confusion.
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Re: Obsidian Aqua, catechol staining developer
Thanks for sharing the formula for this developer. It looks inexpensive for such a large quantity, and the long shelf life is a great reason for me to conder its use. I've ordered some catechol and already have the others. I look forward to trying it in the near future.
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Re: Obsidian Aqua, catechol staining developer
Chris, I'm always happy to share my work, and I hope others find it useful. OA is very inexpensive, and a little goes a long way. It can be a little tricky to measure out tiny volumes required for small tanks, due to the high concentration of the stock solution. A graduated pipette can make things a lot easier, and the bulb type are accurate enough for photo work. The first time you measure out 0.6ml for 300ml of solution can be a little unnerving, but after a few times, you get used to it.
Feel free to contact me directly at:
jdefehr@gmail.com
with any questions or comments. Good luck!
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
Dakotah Jackson
Any results from brush development in flat bottom trays?
Compared to Sandy King's Pyrocat HD, what would I expect to see that you would call an improvement - and viewable in the final print?
Brush development works very well with OA. Compared to Pyrocat HD, OA is sharper, finer grained, produces less fog/general stain, and more compensation with intermittent agitation.
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
Jay DeFehr
Chris, I'm always happy to share my work, and I hope others find it useful. OA is very inexpensive, and a little goes a long way. It can be a little tricky to measure out tiny volumes required for small tanks, due to the high concentration of the stock solution. A
graduated pipette can make things a lot easier, and the bulb type are accurate enough for photo work. The first time you measure out 0.6ml for 300ml of solution can be a little unnerving, but after a few times, you get used to it.
Feel free to contact me directly at:
jdefehr@gmail.com
with any questions or comments. Good luck!
A 1.0 cc syringe is graduated to 0.01 cc, so it should be accurate enough.
m
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
Michael Cienfuegos
A 1.0 cc syringe is graduated to 0.01 cc, so it should be accurate enough.
m
Yes, I use both. A syringe is more convenient for solutions in TEA or glycol, but a pipet is more convenient for aqueous solutions.
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Re: Obsidian Aqua, catechol staining developer
This sounds like an interesting developer. However, the terms "low frequency" and "intermittent" agitation have been used here and are confusing me. Jay, can you define these terms more precisely? I assume that they mean more frequent agitation than stand (agitation for only the first 1 or 1 1/2 minutes after the developer is added) or semi stand (initial agitation plus one agitation cycle halfway through development.) Thank you in advance for the clarification, and for sharing your research.
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Re: Obsidian Aqua, catechol staining developer
Hi Dan. I think you have the gist of it. Agitation frequency ranges from continuous at the high end, to stand at the low end, with a range of frequency in between. I consider "normal" agitation frequency to be the Kodak standard of 5 seconds every 30 seconds, or Ilford's standard of 10 seconds every minute, though this standard should not be thought of as the mean or median between the extremes. Low Frequency Agitation would be below these standards, and High Frequency Agitation above. Gordon Hutching's recommended agitation frequency of 5 seconds every 15 seconds would qualify as High frequency agitation, and all the various schemes such as semi-stand, minimal, extreme minimal, etc., would qualify as Low Frequency Agitation, meaning less frequent than standard.
Agitation frequency can be visualized as a wave form, with rest periods alternating with agitation periods, and the amplitude of the wave as the vigor of the agitation. If, for example, we take an agitation scheme of continuous gentle inversions for 30 seconds, followed by 1 gentle inversion every 3 minutes, we could visualize this as a low frequency, low amplitude wave, and might be appropriate for a dilute developer and a high contrast scene. Another scheme might be to vigorously shake the tank for 30 seconds, and then to repeat for 5 seconds every 15 seconds, and we could visualize this as a high frequency, high amplitude wave that is typical for Technidol and Technical Pan development.
This is probably more than you care to think about agitation, and to some extent it's more theoretical than practical, but there is a practical basis with a developer like Obsidian Aqua that is more sensitive to agitation than general purpose developers are. Visualizing agitation as a wave form with both frequency and amplitude has helped me to theorize about agitation schemes, and to test my theories, but it might be of little or no interest to anyone else. I hope I've answered your questions without putting you to sleep!
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Re: Obsidian Aqua, catechol staining developer
I was hoping this thread would continue on as I am very interested in mixing up and trying a batch. So I will provide a bit of agitation...
Jay: thank you very much for your detailed reply. After reading it and rereading the entire thread, I am assuming that you recommend the "geometric" agitation plan that you discussed in your original post? With that agitation, where do you suggest I begin for an N development time with Ilford HP4 Plus?
Anyone else: have you tried this yet and what are your impressions?
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Re: Obsidian Aqua, catechol staining developer
I was hoping this thread would continue on as I am very interested in mixing up and trying a batch. So I will provide a bit of agitation...
Jay: thank you very much for your detailed reply. After reading it and rereading the entire thread, I am assuming that you recommend the "geometric" agitation plan that you discussed in your original post? With that agitation, where do you suggest I begin for an N development time with Ilford HP4 Plus?
Anyone else: have you tried this yet and what are your impressions?
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Re: Obsidian Aqua, catechol staining developer
Hi Dan,
I'm experimenting with the geometric agitation scheme, but I'm not sure I can recommend it as having any practical advantage over more typical schemes. I'm not sure whether you mean FP4+, or HP5+.
For FP4+, try OA 1:500, 9:00, 70F, with a geo sequence of 30 seconds initial agitation followed by 10 seconds at 2:00, 4:00, 8:00, or a more standard sequence of 2:00, 4:00, 6:00.
For HP5+, try OA 1:500, 15:00, 70F, with a geo sequence of 30 seconds initial agitation followed by 10 seconds at 3:00, 6:00, 12:00, or a more standard sequence of 3:00, 6:00, 9:00, 12:00.
These are WAGs based on my experience with other films, and not on testing these films, so don't commit important films to these recommendations. Optimum development produces a negative with a density range suitable for the printing process, so one must know the exposure scale of the printing process, and the brightness range of the scene to determine best exposure and appropriate development. My WAGs should give you a printable image upon which to base further adjustments to exposure, development, and agitation. Be aware these low frequency agitation schemes will produce pronounced edge effects that might not be suitable for all images.
If you're wary of making up a liter of OA (quite a commitment), you can make 100ml:
Distilled water 70ml
Metabisulfite (sodium or potassium) 2g
Catechol 25g
Distilled water to 100ml
This will make 50 liters of 1:500 working solution, which should be enough to give you a good feel for its characteristics and working properties.
Good luck, and feel free to contact me with any questions or comments, here, or directly at:
jdefehr@gmail.com
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Re: Obsidian Aqua, catechol staining developer
Jay: thank you for suffering a fool; I meant to write FP4+.
I appreciate the starting development times; and I do plan to just expose a few sheets on something mundane near my home for testing, I also was thinking of making up a small batch to play with.
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Re: Obsidian Aqua, catechol staining developer
Is this not just a very minor variation on pre-WWII Pyrocatechin developers ?
Ian
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Re: Obsidian Aqua, catechol staining developer
Dan,
If that makes you a fool, I'm a founding member of that club! Good luck!
Ian,
There are many, many developers based on catechol; some use carbonates while others use hydroxides, some are staining developers, some are not, some are 2-bath developers, and all are variations on the same theme; that theme being catechol as the sole developing agent. Catechol staining developers that include a secondary, or multiple developing agents is a new theme of dubious value.
Whether my variation is major or minor (or very minor) depends on your criteria. Differences among developers that share common ingredients might appear to be minor, but the effects of varying proportions and concentrations can be dramatic. Catechol + hydroxide + KBr can be used to make a very effective lith print developer, or an equally effective compensating film developer by just such variations.
Pre-WWII films were much different than the films we use today, especially the newest technology films, like TMY-2 and Acros, etc. One might be able to take a pre-WWII catechol/carbonate film developer and adjust dilution alone to give acceptable results with modern films, but that seems a pointless limitation. These kinds of developers are so simple, it just makes more sense (to me) to start with a set of design goals and try to achieve them in the most direct way possible. This is what I've done with Obsidian Aqua, and it should come as no surprise to anyone that OA bears a family resemblance to other developers of its kind.
Some differences:
OA is the most concentrated developer of its kind. This strategy achieves two design objectives: improved keeping properties, and improved image stain. Increasing the concentration of the stock allowed me to increase the ratio of developing agent to preservative in the working solution for improved staining, while simultaneously decreasing the ratio of preservative to total solution volume in the stock, for improved keeping.
OA uses a lower concentration of carbonate than other developers of its kind. Modern films don't require the high carbonate developers pre-WWII films did, so OA works at a pH 10X or more, lower than pre-WWII developers, and requires no restrainer.
OA working solution is more dilute than other developers of its kind. Pre-WWII developers typically used 2 or more grams of catechol per liter of working solution, while OA uses 0.5g per liter. A more dilute solution is more prone to local exhaustion during development, and the edge and compensating effects that result from local exhaustion. This in turn increases the appearance of sharpness in the negative and the print.
Taken together, the above combine to form a very different developer. One couldn't make a pre-WWII developer perform like OA without adjusting it to become OA.
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
Jay DeFehr
OA uses a lower concentration of carbonate than other developers of its kind. Modern films don't require the high carbonate developers pre-WWII films did, so OA works at a pH 10X or more, lower than pre-WWII developers, and requires no restrainer.
Thanks for this thread, Jay.
How do you think OA will go with the more traditional/old style films, such as Adox/Efke?
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Re: Obsidian Aqua, catechol staining developer
Hi Lachlan,
Even our "old style" films are very modern compared to pre-WWII stuff, and OA will work very well with them. Ilford PF+ is a fairly "old-style" film, and one of my favorites with OA. Foma films look great, too. I'll try some of the Efke/Adox stuff when I get home, but I'm very confident it will look great. These films benefit from a tanning/hardening developer like OA, and can be extremely sharp. OA is cheap-- give it a go!
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
Jay DeFehr
Hi Lachlan,
Even our "old style" films are very modern compared to pre-WWII stuff, and OA will work very well with them. Ilford PF+ is a fairly "old-style" film, and one of my favorites with OA. Foma films look great, too. I'll try some of the Efke/Adox stuff when I get home, but I'm very confident it will look great. These films benefit from a tanning/hardening developer like OA, and can be extremely sharp. OA is cheap-- give it a go!
Thank again, Jay.
This seems to be a set of chemicals easily (although not initially cheaply) available in Australia (the Catechol if $65 for 100g!!). However, with the dilutions you recommend, this will amotise into a very cheap brew quite quickly.
So much easier to do this that wait for PF to send through some of their Pyro kits...
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
Lachlan 717
Thank again, Jay.
This seems to be a set of chemicals easily (although not initially cheaply) available in Australia (the Catechol if $65 for 100g!!). However, with the dilutions you recommend, this will amotise into a very cheap brew quite quickly.
So much easier to do this that wait for PF to send through some of their Pyro kits...
Lachlan,
I had no idea catechol is so expensive in Australia. It seems it would be cheaper to order it in from Artcraft at US$26.00/ 250g + shipping. This is a major motivation for this formula. Metabisulfite, carbonate and water are available almost everywhere, and a little catechol goes a long way, so shipping catechol alone shouldn't be prohibitive. I hope you can find a better deal on your catechol. Good luck, and let me know if I can be of any help.
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Re: Obsidian Aqua, catechol staining developer
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
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Re: Obsidian Aqua, catechol staining developer
Very interesting...
Thanks for sharing Jay
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
Cor
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.
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Re: Obsidian Aqua, catechol staining developer
Thanks Jay!
I'll report back (although it will be 35mm...:)..)), I just have to wait for sufficient light outside right now,
Best,
Cor
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Re: Obsidian Aqua, catechol staining developer
Hi Cor,
If you shoot in flat light, you might want to increase development a little. I think you'll like this combination.
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Re: Obsidian Aqua, catechol staining developer
Quote:
Anyone knows where you get catechol in Canada?
/gth
You can get catechol from Nymoc in Toronto. Email John Burrows: nymoc@bellnet.ca
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Re: Obsidian Aqua, catechol staining developer
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.
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Re: Obsidian Aqua, catechol staining developer
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
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Re: Obsidian Aqua, catechol staining developer
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
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1 Attachment(s)
Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
gth
3. Also... has anyone used OA on X-ray film emulsions?
Attachment 73238
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/
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
gth
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
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Re: Obsidian Aqua, catechol staining developer
Quote:
Originally Posted by
Jay DeFehr
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.