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Rudeofus
02-11-2012, 02:20 PM
It has already been stated that Ferric ion in water will rapidly oxidize AA.
I didn't question this. The question was whether 1% (or 3% or 5%) of water in propylene glycol or TEA plus some iron impurities would do the same to AA. Would the ion salts disassociate into ions in such a liquid and would they catalyze the reaction?

Photo Engineer
02-11-2012, 02:26 PM
Well, if it is catalytic, then a tiny amount of Iron III will do the job. It just keeps on going and going.

PE

Rudeofus
02-11-2012, 02:48 PM
Well, if it is catalytic, then a tiny amount of Iron III will do the job. It just keeps on going and going.
But would it ionize in PG with 1% water?

Alan Johnson
02-11-2012, 03:24 PM
I measured the current between iron and zinc about 1cm square, it was only 5 microamps in 10g/L sodium ascorbate.
In 99% PG +1%water it would need an electrometer to measure.
If an accelerated test was wanted some form of corrosion test would probably be more practical to get an idea of the rate of oxidation in presence of water of crystallisation.

Kirk Keyes
02-11-2012, 05:16 PM
Sounds like it's time to get a redox probe and learn what joys are involved in making redox measurements!!!

albada
02-12-2012, 09:51 AM
After sitting a few days, the extreme concentrate became slightly milky. The milkiness was throughout the liquid, not just at the surface. So I did the obvious and reheated it to redissolve the precipitate. Only it did not dissolve, but became more milky upon heating. Much more milky. Apparently, some chemical reaction had started, and heating accelerated it. The milkiness vanished when some concentrate was mixed with sulfite-laden water. The pH was correct, and it developed a test-strip fine, albeit a little thinner than one developed by directly-mixed chemicals. So it's hard for me to say if the ascorbate is being damaged. Any guess on the cause of milkiness?

Thanks,

Mark Overton

Athiril
02-16-2012, 01:10 AM
The TEA is also a chelating agent and with the salicylic acid seems to increase the chelation of iron.

Iron is a common impurity of many inorganic chemicals and so you cannot get around not using a chelating agent just by mixing the developer with distilled water. Salicylic acid can be obtained from many compounding pharmacies. It shouldn't be expensive. I purchased 250 g a few years ago for $1o. TEA can be purchased from such locations as www.chemistrystore.com.

If you can't get your hands on salicylic acid, you can find it in various skin creams and solutions at weak dilutions.

Otherwise hydrolysis of aspirin yields salicylic acid. Which is very handy.

albada
02-16-2012, 08:19 PM
Two questions for the experts. The second presents an interesting formula, and I'm wondering why it works well.

(1) What does boric acid do to image-quality? Crawley claimed it removed a "borax sheen", but folks can't seem to substantiate that with modern films. Should it be considered as merely a way to reduce pH? I know it buffers well with alkaline borates, but I'm wondering if there's anything else beneficial or harmful about it.

(2) Does the "solvent effect" actually peak at a fixed grams/liter? I'm thinking of Gerald Koch's statement here (http://www.apug.org/forums/forum37/101034-formulating-sharp-solvent-mq-developer-2.html) that "Maximum solvency of sulfite to silver halide actually occurs at about 70 g/l". If sulfite is increased over 70 g/L, does solvent effect stop rising or even decrease? If so, is this peak time-dependent?

As an example of what can be done with a small amount of sulfite, the formula below uses only 30 grams/liter of sulfite, and yet gives the same grain and shadow-detail as XTOL 1+0:



Sodium sulfite ...................... 30 g
Sodium metaborate 4 mol ....... 2.4 g
Ascorbic acid ....................... 4.5 g
Phenidone ........................... 0.05 g -or- 0.1g of Dimezone S

Target pH is 7.9. Starting dev-time is XTOL's time multiplied by 2.3.


The downside of this formula is long dev-time: Tmax-400 needs 15 minutes at 20C. For comparison, XTOL 1+0 has 88 grams/liter of sulfite and needs only 6.5 minutes for TMY-2. With only 30 g/L of sulfite, you would think this formula would be grainier and slower than XTOL due to lack of solvent effect (its sulfite is well below 70). Yet grain and speed match. I'm wondering why.

Mark Overton

Photo Engineer
02-16-2012, 10:28 PM
I am not sure about your two questions, but there is a curve of Sulfite solvency that involves pH and Sulfite concentration. So the answer is "it varies".

As for long development times, I said earlier that Kodak's last R&D indicated that long development times were better. So my question is this "What's your hurry?".

PE

albada
02-16-2012, 11:57 PM
I am not sure about your two questions, but there is a curve of Sulfite solvency that involves pH and Sulfite concentration. So the answer is "it varies".

Your responses are always appreciated.

I was wondering what boric acid might do to image-quality. It's attractive for a concentrate because it'll dissolve into propylene glycol. Such an acid will allow more alkali to be used to improve buffering. A borate buffer is the obvious choice. Is there an organic acid which will form a good buffer with TEA?

Is that sulfite solvency curve published somewhere? I have Mason and others, but not Haist. I've been experimenting with sulfite-levels. The low levels need long dev-times to avoid stressing the weak buffering, and I guess long times allow for sufficient solvent effect. Gerry had posted that solvent effect peaks at 70 g/L, so I was wondering if other factors were involved too, such as time. You mention pH.



As for long development times, I said earlier that Kodak's last R&D indicated that long development times were better. So my question is this "What's your hurry?".PE

It took a lot longer to shoot the roll than to soup it, so I guess no hurry.

I'm leaning toward having two concentrates:

(1) One that minimizes chemistry, but with XTOL's image quality. The example shown two postings ago gives the quality of XTOL 1+0, and yet uses less chemistry than XTOL 1+1. My frugal personality likes that. :)

(2) One that maximizes image quality. This will use more sulfite for sure...

Mark Overton

Rudeofus
02-17-2012, 02:59 AM
I was wondering what boric acid might do to image-quality. It's attractive for a concentrate because it'll dissolve into propylene glycol. Such an acid will allow more alkali to be used to improve buffering. A borate buffer is the obvious choice.
I am not a chemist but from my little knowledge boric acid shouldn't do much harm to your photos. Remember that the same ions are also present from metaborate, and if metaborate doesn't hurt boric acid shouldn't either (pH value aside, of course).

Is there an organic acid which will form a good buffer with TEA?
Again, take my advice with a big grain of salt, but from looking at it salicylic acid and benzoic acid should both dissolve in TEA and are weak acids, i.e. should work nice as buffers.

Is that sulfite solvency curve published somewhere?
IIRPEC (if I read PE correctly) the solvent action of Na2SO3 depends on various factors, amongst them pH value of your soup but most likely also the kind and composition of silver halide in your film. If you have a restrainer in your dev, it changes again. The curve you look for is a plane of sufficiently high dimension that all our heads would explode from just peeking at it. We don't want that :p

One thing that I have been wondering is why everybody is so focused on the solvent capability of sulfite when we all know and use a much more potent solvent shortly afterwards: thiosulfate. Wouldn't thiosulfate work as weak silver solvent in low concentrations? Changing the sulfite to thiosulfate ratio should allow us to nicely balance their properties. As most mono bath recipes show, thiosulfate doesn't necessarily eat all your silver halide away before the dev can act.

Photo Engineer
02-17-2012, 10:45 AM
The Sulfite curve is an informal piece of information that I have heard discussed but have never seen published. I have seen grain and sharpness data that support it though. That is the best I can say.

We did compare Borate with Carboante mole for mole and found that they were almost identical in their photographic characteristics. So, I would say you are "safe" using Borate from this POV. And, converting to TEA should be simple as many liquid developer today use TEA + Borate or TEA + Carbonate.

PE

albada
02-18-2012, 04:30 PM
Here's another for the experts:

What determines the capacity of a developer?

I just dev'd a roll in this developer (http://www.apug.org/forums/viewpost.php?p=1303637) shown five postings above, and the developer turned orange and the roll was underdeveloped. The density of the leader was .25-.3 below what it should be, and edge-markings were thin as well. Yet this developer handles a test-strip fine, so I conclude that 225 ml of this formula can't handle a 36-shot roll. BTW, pH was virtually unchanged at 7.97 before and 7.95 after.

PC-Sulfite (here (http://www.apug.org/forums/forum37/99921-pc-sulfite-simple-developer-giving-xtol-quality.html)) didn't have this problem, and it has less ascorbic acid than this test-developer, so the amount of ascorbic isn't the issue.

Kodak recommends a minimum of 100 ml for XTOL, which is 8.8 grams of sulfite. My formula used 6.75 grams (for one roll), which isn't much lower. My dev-time was longer (15 min), which I thought would have helped things. I know that sulfite does several good things for developers, and removal of oxidation products of the developer is one of them. So perhaps a little more sulfite would help?

BTW, the word "capacity" is not in the index of Mason or Mees-James. But Mason pg 122 says "the amount of sulphite required for this purpose [of removing oxidation products] is usually quite small, the quantities normally employed in the usual type of black and white developer solution being more than adequate." Unfortunately, he didn't supply any numbers.

It would be nice to know not only how to fix this capacity-issue, but also why it's occurring. I'll guess that more sulfite would remove more oxidation products, but that's just my half-educated guess...

Thanks,

Mark Overton

Photo Engineer
02-18-2012, 06:52 PM
There are two major factors in developer capacity. One is the "buffer capacity" and the other is the "developing agent capacity". Both are interrelated and can usually only be determined by experiment.

Here is an example of Buffer Capacity. Make 2 solutions up with Kodak, one at 5 g/l and the other at 50 g/l. Adjust both to pH 10.1 at 20 deg C. Both have the same pH, but at 50 g/l the second has 10x the buffer capacity and if used to make a developer can process 10 - 20x the square footage of film or paper than the example with 5 g/l. And, any pH drop in the first example may be tiny.

Developing agent capacity works the same way, but usually changes the contrast and so you usually only see this in unbalanced mixes of 2 developing agents in which one agent is too low or the ratio is right but the level is low. This one is really tough to work out.

I have worked with both types of problem and the first is really a no-brainer if that is your problem. If not, it is the second problem and that one is a real b**ch to work out.

Of course, aerial oxidation may also be creeping in here and causing you problems.

PE

albada
02-19-2012, 12:02 AM
There are two major factors in developer capacity. One is the "buffer capacity" and the other is the "developing agent capacity". Both are interrelated and can usually only be determined by experiment.

Here is an example of Buffer Capacity. Make 2 solutions up with Kodak, one at 5 g/l and the other at 50 g/l. Adjust both to pH 10.1 at 20 deg C. Both have the same pH, but at 50 g/l the second has 10x the buffer capacity and if used to make a developer can process 10 - 20x the square footage of film or paper than the example with 5 g/l. And, any pH drop in the first example may be tiny.

Developing agent capacity works the same way, but usually changes the contrast and so you usually only see this in unbalanced mixes of 2 developing agents in which one agent is too low or the ratio is right but the level is low. This one is really tough to work out.

I have worked with both types of problem and the first is really a no-brainer if that is your problem. If not, it is the second problem and that one is a real b**ch to work out.

Of course, aerial oxidation may also be creeping in here and causing you problems.

PE

Wow!
What a great response.
I encourage you to write a book or article titled, "Designing film-developers".

After reading your response, I shot another roll and dev'd it in the same developer, but doubling the sulfite (60 g/L vs 30), and adding citric acid to drop pH back to 7.95. I figured that this would improve the buffering enough to fix the problem.
Result: Orange developer! But density is improved, albeit not quite up to normal. Very fine grain. Outstanding image-quality.

Looks like I've got the "real b**ch" problem: Insufficient developer. The phenidone is only 0.05 g/liter, which I guess isn't enough. But given how good the image-quality is, maybe I'll boost phenidone a mild amount, along with the ascorbic acid to keep their ratio constant, and see how it goes.

Here's an interesting idea: Deliberately let the dev-agents be destroyed during development. This will cause them to be most active during the early part of development, and slow down near the end when grains are getting large. Perhaps this will reduce filament-formation and thus reduce grain. Physical development would presumably be more prominent near the end (i.e., higher physical/direct ratio). Or has this idea already been tried and rejected?

Mark Overton

Photo Engineer
02-19-2012, 10:26 AM
What you describe Mark is often used in dilute or stand development to enhance edge effects as the developing agent is used up.

PE

Rudeofus
02-19-2012, 02:17 PM
Here's an interesting idea: Deliberately let the dev-agents be destroyed during development. This will cause them to be most active during the early part of development, and slow down near the end when grains are getting large. Perhaps this will reduce filament-formation and thus reduce grain. Physical development would presumably be more prominent near the end (i.e., higher physical/direct ratio). Or has this idea already been tried and rejected?

For this method to work you'd have to know how much silver halide you are going to reduce, and you normally don't know this until you go the images developed.

Next problem is that if the developer runs out of oompft (and let's assume decent agitation), the strongly exposed parts of your film will be already developed, while the weakly exposed parts won't. With this method, you will lose speed, develop mostly the largest grains and boost contrast somehow. Not sure if there's much use for that ....

albada
02-19-2012, 03:32 PM
For this method to work you'd have to know how much silver halide you are going to reduce, and you normally don't know this until you go the images developed.

Next problem is that if the developer runs out of oompft (and let's assume decent agitation), the strongly exposed parts of your film will be already developed, while the weakly exposed parts won't. With this method, you will lose speed, develop mostly the largest grains and boost contrast somehow. Not sure if there's much use for that ....

I'll keep experimenting with this formula. At a minimum, I'd like to characterize what's causing this usually fine grain, whether exhaustion or some aspect of the chemistry. And as Rudeofus says, exhaustion is hard to control, so I'm hoping it's the formula.

BTW, after sitting in an open beaker for half a day, the orange developer became water-clear. Perhaps aerial oxidation rejuvenated it? :)

Mark Overton

Rudeofus
02-20-2012, 03:47 AM
I'll keep experimenting with this formula. At a minimum, I'd like to characterize what's causing this usually fine grain, whether exhaustion or some aspect of the chemistry. And as Rudeofus says, exhaustion is hard to control, so I'm hoping it's the formula.
You could always try using the same formula, just use more soup with the same amount of film. Put one roll of film in a tank which holds 2 or even better 4 rolls, completely fill it with dev and see what happens. If you don't have a larger tank, try swapping out the dev a few times during the process. Since your test strip didn't trigger the exhaustion phenomenon yet showed good grain there is a good chance that exhaustion was not the driving factor.

BTW, after sitting in an open beaker for half a day, the orange developer became water-clear. Perhaps aerial oxidation rejuvenated it? :)
The orange color could come from sensitizing dyes. I know when I develop color silde film that the first dev takes on all kinds of colors which do disappear after a while. Many factors could cause this: oxidation from aerial oxygen, slow reduction in remaining dev, exposure to light, or some combination of these.

albada
02-20-2012, 02:08 PM
Totally off-topic: My Densa posting here (http://www.apug.org/forums/forum37/102124-densa.html) is probably getting little attention because most people don't know what's in there due to my poor title. It's my idea of humor. But I digress. Back to the topic at hand...


You could always try using the same formula, just use more soup with the same amount of film..

Looks like I'll need to do the equivalent: Put more developer into each liter. I'd like the dev to work conveniently with 1-roll tanks.


The orange color could come from sensitizing dyes. I know when I develop color silde film that the first dev takes on all kinds of colors which do disappear after a while.

Then shouldn't XTOL also come out orange? In fact, it comes out almost clear.

Well, I've devised a new concentrate that boosts the phenidone/dimezone by 50%, and the alkali/acid by 33%. As a concentrate, it would have 1+39 dilution.
Most of my testing is with 1.5-frame test-strips, but testing a whole roll at a time sure burns up film fast. It also gives me an excuse to take a bunch of pictures. :)

Mark Overton