Improved version of DS-10 by Ryuji Suzuki?

[albada]

Thanks for the interesting info about pH-probes. I ordered a compatible replacement, which lets me procrastinate on hacking a BNC with its potential problems.

You can drive water out of propylene glycol by heating.

Last night, I verified that one can drive water out of propylene glycol by heating it to close to 100C. My idea came from Tom Hoskinson's observation in this thread:
(there was a url link here which no longer exists)
In it, he states that "If you heat straight propylene glycol to 160F it will give off some water vapor."

This is important to me because sodium metaborate contains some water (as Rudeofus pointed out), and Borax has much more. Plus, some reactions with ascorbic acid produce water. I want as little water in a concentrate as possible to avoid absorbing oxygen and oxidizing developer. So I put 2.5 ml of PG in a beaker, weighed it, and added 1 gram of water. Then I heated it to just under 100C, and weighed it every 5 minutes. Here are the water-weights (ie, initial weight was subtracted):

Min ... Water
0 ...... 1.00
5 ...... 0.76
10 .... 0.32
15 .... 0.16
20 .... -0.08
25 .... -0.16
30 .... -0.23

I could see a wisp of steam rising from the beaker the whole time. The negative numbers mean I lost more than 1 gram, which I attribute to (1) A couple of drops of carry-out on the thermometer-stem, and (2) water in the original PG.
My conclusion: Heating PG drives water out of it.

But a couple of warnings: (1) Keep the temperature below the 99C flash-point of PG. Above that, flammable PG-vapor can run down the outside of the beaker onto the heater and ignite. (2) Staying below 100C also avoids what chemists call a "bump" wherein a sudden bubble of steam blasts hot PG everywhere, including your hands and face. So go ahead and heat your PG-based concentrate to dry it -- but I suggest not going over 90C.

Mark Overton

 

[albada]

My second posting to this thread today...

Last night, I also discovered a way to dissolve a large amount of ascorbic acid into propylene glycol (PG). The trick is to include enough alkali to convert the ascorbic acid into ascorbate. Here's what I mixed:

Propylene glycol ................. 9.75 ml
Ascorbic acid ..................... 5.5 g
Sodium metaborate 4 mol ..... 4.25 g

This is a developer I'm working on, but without the Dimezone in it yet. I chose 9.75 ml of glycol because 9.75 is the weight of the two powders, so the g/ml ratio (powders/PG) is 1.0. I figured there's no way so much powder could dissolve at such a high ratio, so I planned to add more PG as I went. I heated the above to 70-90C, and... you guessed it... it all dissolved! It took 20-30 minutes of constant stirring followed by intermittent stirring, but it all dissolved. And there's no precipitation upon cooling to room-temperature.

So the good news is: You can achieve a very high concentration by converting some/all of the ascorbic acid to ascorbate in situ. For comparison, the g/ml ratio for Gainer's PC-Glycol is only 0.1333. But there's a cost to such high concentration: Its viscosity at room-temperature is like honey or cool pancake-syrup. It's still pourable and measurable, but I don't think I'd want to push that ratio much above 1.0.

Mark Overton

 

[Rudeofus]

You can drive water out of propylene glycol by heating.

Chemists call this distilling, you take advantage of sufficiently different boiling points of two substances and it is a process not only used by chemists

This is important to me because sodium metaborate contains some water (as Rudeofus pointed out), and Borax has much more. Plus, some reactions with ascorbic acid produce water. I want as little water in a concentrate as possible to avoid absorbing oxygen and oxidizing developer.

I think I also pointed out that traces of water barely matter when it comes to trapping oxygen, and I'm not even sure whether trapped oxygen actually mattered that much in such a solution. Pat Gainer apparently mentioned that a few ml of water in the concentrate did not affect shelf live. Sorry, I didn't find the original quote from him.

 

[albada]

I think I also pointed out that traces of water barely matter when it comes to trapping oxygen

What concerns me is the molar ratio of liquids. In my formula at the top of this page, for example, the metaborate will produce 1.13 g of H2O after reacting with the ascorbic acid. That sounds small, but on a molar-basis, that's one third of the molecules of liquid. That's enough to concern me, and is a question for the chemists here: Will a solution of 67% PG and 33% H2O (molar ratios) absorb a significant amount of oxygen?

Pat Gainer apparently mentioned that a few ml of water in the concentrate did not affect shelf live. Sorry, I didn't find the original quote from him.

I seem to recall reading that quote also. He was suggesting adding a little water to PG to help dissolution. But a quantity of water that's small on a volumetric basis is surprisingly high on a molar basis, so I'm being cautious.

I'm thinking that mixing hot PG has two benefits: Speedy dissolution, and removal of water. The question is: Is the amount of water harmful? If not, dissolution can be accomplished using Gerald Koch's method: Let the brew sit for hours at room-temperature, shake the bottle on occasion, and all will eventually dissolve with no heating needed.

Mark Overton

 

[Kirk Keyes]

Will a solution of 67% PG and 33% H2O (molar ratios) absorb a significant amount of oxygen?

OK - I'm a chemist that has worked with dissolved oxygen in water.

At 20C, a saturated solution of oxygen in water has a concentration of 9 mg of oxygen per liter of water. That's a saturated solution. A supersaturated solution can have a higher concentration of oxygen in it, but it will loose oxygen until it becomes a saturated solution. And as the temperature of the water goes up, the solubility of oxygen in it rapidly decreases.

I can't say what effect having glycol in there will do to the solubility of oxygen in water.

A liter of water really can't hold a lot of oxygen. What kills developers is exposure to oxygen through permeable bottles and caps, poorly sealed bottles, or agitation of the developer in an oxygen environment. Like using bottles fitted with a rubber bulb is a poor choice as a storage container.

Anyone that's used pyro developers can tell you how fast they oxydize in a Jobo tank. And anyone that's used pyro developers in a Jobo tank fitted with a nitrogen-purge line will tell you how well pyro developers can work in a Jobo tank.

 

[Rudeofus]

I can't say what effect having glycol in there will do to the solubility of oxygen in water.

The problem as stated by Mark is exactly the other way round: he has traces of water in glycol. Developer in pure glycol is known to last forever, but he/we would like to know how much water is acceptable in that mix before it deteriorates too fast. Since developer action differs when it's anionic, cationic or not ionized at all, the oxygen content alone may not be the only determining factor.

 

[Alan Johnson]

It might be possible to get some idea of the effect of water content on rate of oxidation by dipping into the concentrate clean pieces of copper and aluminium and measuring the current flowing between them.
Or there is a test for accelerated corrosion in brake fluid:
http://www.mossmotors.com/SiteGraphics/Pages/Brake_Fluid/brake_fluid_long.html
Otherwise it may take months to find the rate of oxidation.

 

[Rudeofus]

It might be possible to get some idea of the effect of water content on rate of oxidation by dipping into the concentrate clean pieces of copper and aluminium and measuring the current flowing between them.
Or there is a test for accelerated corrosion in brake fluid:
http://www.mossmotors.com/SiteGraphics/Pages/Brake_Fluid/brake_fluid_long.html

Brake fluids are tested with metal test strips because that's what's in the break lines or pistons. In our case we deal with reducing agents which work differently depending on their state of ionization. To my best knowledge, ascorbic acid lasts for a long time as a powder even if oxygen is present, yet deteriorates quickly in aqueous solution. That oxygen trapped in the glycol/water may or may not attack the ascorbic acid (or whatever dev) in there. Another factor may be catalysts: some dev deterioration processes happen rapidly if certain ions are present (e.g. iron & ascorbic acid). I don't know whether this reaction takes place in water contaminated glycol/TEA/...

 

[Photo Engineer]

It has already been stated that Ferric ion in water will rapidly oxidize AA.

PE

 

[Rudeofus]

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]

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]

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]

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]

Sounds like it's time to get a redox probe and learn what joys are involved in making redox measurements!!!

 

[albada]

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]

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]

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 (there was a url link here which no longer exists) 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]

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]

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]

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

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]

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]

Here's another for the experts:

What determines the capacity of a developer?

I just dev'd a roll in (there was a url link here which no longer exists) 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 ((there was a url link here which no longer exists)) 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]

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]

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]

What you describe Mark is often used in dilute or stand development to enhance edge effects as the developing agent is used up.

PE