Progress on XTOL-concentrate

Photo Engineer · Oct 29, 2012

Mark;

We typically used small strips (35mm x 12") to check new coatings and new chemicals out. Then we processed a full roll. I have never seen this happen. These were 1 L to 2 L tanks for the strips and about 2L - 4L for the full rolls. We used both hand agitation (dip and dunk) and Nitrogen burst, and these were all comparable.

I have no explanation.

PE

albada · Oct 29, 2012

Photo Engineer said:
Mark;
We typically used small strips (35mm x 12") to check new coatings and new chemicals out. Then we processed a full roll. I have never seen this happen. These were 1 L to 2 L tanks for the strips and about 2L - 4L for the full rolls. We used both hand agitation (dip and dunk) and Nitrogen burst, and these were all comparable.
I have no explanation. PE

Here are the curves between the test-dev and XTOL. Note that the test-dev *strip* matched XTOL well. On these rolls, I shot the Stouffer wedge twice, the second with longer exposure, and thus was able to catch the shoulders:

Notice that XTOL has an abrupt shoulder, and that the test-dev shoulders-off gently, giving more useful dynamic range. We know about the trade-off between contrast/grain/sharpness. I'd like to add another item to that list: dynamic range. This test-dev would show detail in clouds better due to its gentler shouldering.

Also, I thought I accidentally developed the roll for one minute too long, so I did it again. Here's are the curves for the two rolls:

This gives you an idea of the repeatability of my work. And it shows that the time is correct (nuts!).

This dev contains some propylene glycol, which is a difference from XTOL and other dev's that Kodak developed. I noticed that PG retarded development, so my 12.25 minute time increased to 13.1 minutes (keeping pH constant). Ratios of the curves above tell me the time should be 12.1-12.3 minutes, which is where it originally was. Could a roll undo the PG-retarding?

Mark Overton

EDIT: Rudi, I'll remember to measure before/after pH for the next roll and see if it rises.

Photo Engineer · Oct 29, 2012

Mark;

I would say that these rolls (Xtol vs your developer) differ in contrast. If your developer had shorter time or Xtol longer, they would match more closely. I think that this may be the situation.

PE

Alan Johnson · Oct 29, 2012

albada said:
I'll guess that the by-products of the phenidone and AA accelerate development. I remember reading about this, but this is the first time I've seen it.

Mark Overton

Not according to Pat Gainer, see post#20.The phenidone is not used up, ascorbate is converted to the more acidic dehydroascorbate.
(there was a url link here which no longer exists)
It's hard to find the original source for this information.

Rudeofus · Oct 29, 2012

Alan Johnson said:
Not according to Pat Gainer, see post#20.The phenidone is not used up, ascorbate is converted to the more acidic dehydroascorbate.

There is plenty of published literature available online, and it suggests that dehydroascorbate is not the end of the story, especially in alkaline solution. Also, at pH of 8 it doesn't matter much whether some acid has pKa of 1 or 5, it will be fully protonized anyway. The question remains how many protons are produced or consumed in the various redox reactions of Ascorbic Acid and how many protons the resulting compounds will let go at pH around 8.

A pH measurement before and after development sounds easier ...

albada · Oct 30, 2012

Rudi: pH before and after development were 8.17 and 8.13, a drop of .04.

PE: You suggested reducing dev-time. I ran another roll this evening (and got the above numbers for Rudi), but with the shorter dev-time of 12:15 minutes. The graphs of XTOL vs the baseline developer:

It's an excellent match with XTOL, and with slightly better performance near the shoulder. Leader densities are 2.70 for XTOL, and 2.75 with the latest roll. Grain in the baseline dev looks slightly finer than XTOL in loupes.

The remaining mystery is: Why does developing an entire roll require less time than just a test-strip to achieve the same densities? The pH drops instead of rises during development, so rising pH from by-products isn't the reason. XTOL doesn't need less time, and the only substantial chemistry differences are (1) the presence of propylene glycol, and (2) ascorbic acid instead of ascorbate.

Alan suggested that the pH would drop, and it did. I wish I had a deep enough understanding of the underlying chemistry to figure out this stuff. I have books, and plan to re-read the O-chem chapter.

Mark Overton

Rudeofus · Oct 30, 2012

Mark,

it would be worthwhile looking at whether a pH drop of 0.04 has that much effect on contrast. You could try a few test clips all with the same time but with pH varied through 8.1, 8.14, 8.18, 8.22.

If you see a big difference, it might be worth investigating what Xtol does differently. You could also try and compare buffer strength of Xtol vs. your dev, which can be done by preparing a small quantity of both, measuring their pH, then putting same amount of acid into the liquids, then measuring pH again.

Photo Engineer · Oct 30, 2012

IMHO, that pH drop would be insignificant in the face of the actual results.

I am still at a loss to explain it. It is known that some polyols affect development. I don't think that is the explanation though.

PE

Alan Johnson · Oct 30, 2012

albada said:
The remaining mystery is: Why does developing an entire roll require less time than just a test-strip to achieve the same densities?

Mark Overton

Are you still using the test strip set-up described in post#110?
(there was a url link here which no longer exists)
Perhaps the flow across the emulsion is different for test strip and roll.

Gerald C Koch · Oct 30, 2012

It's dangerous to make conclusions from a single data point. Does this always happen that a full roll develops faster than a test strip?

albada · Oct 30, 2012

Alan, I'm using a different baffle now, but the same concern is true of it: Flow will be different compared to a roll. The odd thing is: With XTOL, the graphs for strip and roll match. But with my dev, a strip needs more time.

Gerald C Koch said:
It's dangerous to make conclusions from a single data point. Does this always happen that a full roll develops faster than a test strip?

Three rolls have confirmed this. I wondered if I'd made a mistake with the first roll, so I ran a second -- with identical results. Last night, I ran a third roll with a shorter dev-time, and it matched XTOL's graph well. Here's a summary of what I've run (with and without adding propylene glycol):

XTOL strips and roll -- gave nearly identical graphs.
Strips with no added PG: 12.25 min is correct (where "correct" means "matches XTOL's graph").
Strips with added PG: 13.1 min is correct.
Rolls with added PG: 12.25 min is correct.

It's acting as if having a low fluid-to-film ratio quickly neutralizes the retarding effect of the PG, causing development to proceed at its normal (higher) rate.

Mark

Alan Johnson · Oct 30, 2012

With Xtol they are the same because the high ascorbate concentration is enough to regenerate phenidone "oxide" adsorbed on silver.
With Xtol concentrate working solution the strip is not getting enough ascorbate to regenerate adsorbed phenidone "oxide".The lower concentration of ascorbate in the concentrate working solution means its diffusion is more affected by the difference in flow patterns.

Photo Engineer · Oct 30, 2012

I note in your experiment Mark that there is no roll with no added PG. So, what if that one differed in the same way in time? Do we know that?

PE

albada · Oct 31, 2012

Photo Engineer said:
I note in your experiment Mark that there is no roll with no added PG. So, what if that one differed in the same way in time? Do we know that? PE

Hmm, I haven't tested that case. I'll try to run an experiment tomorrow night (on All Hallows' Eve) to see what no PG does for a roll.

Alan: A strip has more flow over it than an entire roll, so I'd expect strips to be denser than a roll. But for this dev, strips were thinner. Strange indeed! An odd thing is that the more concentrated formula that crystallized back in July ((there was a url link here which no longer exists)) didn't have this time-issue.

Mark Overton

EDIT: It's been a while, so I figured I'd repost the formula for the concentrate we're talking about:

Propylene glycol .................... 17 ml (hot; a little below 100C)
Sodium metaborate 4 mol ..... 2.7 g
Ascorbic acid ......................... 4.5 g
Phenidone ............................. 0.05 g
Propylene glycol to make ...... 22 ml

One litre of working solution contains 45 g of sodium sulfite and 25 g (22 ml) of concentrate.
Target pH = 8.18-8.19.

Photo Engineer · Oct 31, 2012

You know that if you don't test that new alternative, it will haunt you!

PE

albada · Nov 1, 2012

Photo Engineer said:
You know that if you don't test that new alternative, it will haunt you!
PE

I got spooky test-results! I mixed the formula again, but omitting the PG and decreasing the sodium metaborate by .1 g/L to maintain the same pH. Here are the curves with/without PG:

They are eerily identical! At least you can't claim that my process lacks consistency. It makes one wonder if I actually added PG before. My log says so, and I remember measuring the PG. And if I didn't, the lower pH should have gotten my attention.

To summarize what I've seen: Adding 16 ml/L of propylene glycol (that's 1.6% of volume) causes dev-time to increase by 7% for test-strips. But it has no effect on complete rolls. I doubt this is a problem for typical users, but it's something that's haunting me.

Mark Overton

PS: The title on the graph is wrong. I forgot to change that part of the gnuplot script-file.

albada · Nov 4, 2012

Fenton test results

Alan Johnson said:
In the UK the maximum limit for copper in drinking water is 2mg/L and for iron 0.2mg/L.I don't know the US values.
http://dwi.defra.gov.uk/about/annual-report/2009/cir09thames.pdf
I daresay there may be high copper concentations in the UK which has mostly copper pipes and high iron concentrations in the US (which has mainly iron pipes?).

The Fenton test consisted of adding Fe and Cu ions (iron and copper) to the developer to simulate iron and copper pipes, and impurities in chemicals. I added 1 mg/L each of Fe(II) and Fe(III) ions using ferrous sulfate heptahydrate and ferric ammonium sulfate, and 2 mg/L of Cu(II) ions by adding copper sulfate pentahydrate. Jerry: I used ferrous sulfate because PhotoFormulary doesn't carry ferrous ammonium sulfate. Was this change a mistake? The separate beaker of these ions at 100x concentration was a cloudy light-yellow. Surprise: When adding 1 ml of it to the developer, the developer turned light purple. I'll guess the ammonia is reacting with something.

I waited 50 minutes before developing, to simulate easy-going one-shot usage. Here are density-curves with and without these added ions:

The curves match well, so the Fenton reaction had no measurable effect. Nor did the purple, fortunately.
Earlier tests show that hard water causes cloudiness starting at 30-45 minutes after mixing. So all should go well if this one-shot is used within 30 minutes of mixing.
I guess my next step is to mix the concentrate and test its longevity and compatibility with various films. Comments are welcome as always.

Mark Overton

Gerald C Koch · Nov 4, 2012

Hi Mark,

Iron forms a lavender/purple complex with salicylate ions. So it appears that the chelating agents are working. To answer your other question ferrous sulfate oxidizes fairly rapidly particularly in moist air. Ferrous ammonium sulfate is more stable but either should be OK.

I would be interested in what would happen without the chelating agents. Would be ascorbate ion be rapidly destroyed at the concentrations you used. Also the longevity of your developer with the chelating agents and iron and copper present.

Jerry

albada · Nov 4, 2012

Gerald C Koch said:
Hi Mark,

Iron forms a lavender/purple complex with salicylate ions. So it appears that the chelating agents are working. To answer your other question ferrous sulfate oxidizes fairly rapidly particularly in moist air. Ferrous ammonium sulfate is more stable but either should be OK.

I would be interested in what would happen without the chelating agents. Would be ascorbate ion be rapidly destroyed at the concentrations you used. Also the longevity of your developer with the chelating agents and iron and copper present.

Jerry

Hi Jerry, here's a surprise: Yesterday's brew had no chelating agents! I guess I didn't make that clear, but I wanted to see whether it would die quickly with no protection against Fe/Cu ions. Thanks for the note about oxidation of ferrous sulfate. I transferred it to a little amber glass bottle last night, so hopefully it'll keep a while. Anyway, do you know of anything else that would cause the purple? I used distilled water, so there should be no unknown chemicals in there.

Mark Overton

Gerald C Koch · Nov 4, 2012

One of oxidation products of phenidone is magenta in color. But this product shouldn't form in the presence of a reducing agent like ascorbate ion. So I really don't know what caused the color. All the oxidation products of ascorbate are colorless.

albada · Nov 4, 2012

Gerald C Koch said:
One of oxidation products of phenidone is magenta in color. But this product shouldn't form in the presence of a reducing agent like ascorbate ion. So I really don't know what caused the color. All the oxidation products of ascorbate are colorless.

Jerry, thanks for the help. Here are a few more tidbits I just got:

* The purple coloration of the used developer was gone this afternoon; it was water-clear.

* A clip-test from 20 minutes ago with normal temp/time/agitation/stop/fix/wash gave identical results to yesterday, so the dev did not degrade noticeably over 22 hours.

* I divided the used dev into three parts, and put the three ion-producing chemicals into each. This was not measured; just a little bit in each, which was undoubtedly far too much. The Ferrous sulfate gave light purple, and the Ferric ammonium sulfate (FAS) produced a dense purple. Copper sulfate gave no color. So I suspect the colour is due to the FAS.

* I put a little FAS into a beaker and added unmeasured quantities of each chemical in the dev. Nothing produced a purple, so maybe pH matters and I should measure quantities correctly.

A caution:
The FAS from the Formulary was labelled "Ferric Ammonium Sulfate", but the CAS-number on the packet is for Ferric Ammonium EDTA. It came as large crystals covered with white powder. When broken up, their internal colour is slightly pink as is pictured in Wikipedia here, so I think I have the correct stuff.

Well, assuming I don't have the erroneous EDTA in there, it looks like the Fenton reaction is not an issue over the time-frame of one day.

Mark Overton

albada · Nov 10, 2012

Crystallization

I've been experimenting with more concentrates using propylene glycol as the solvent, and characterizing the issue of crystallization. By way of review:

* Paul Verizzo and I independently discovered that sodium metaborate dissolves in propylene glycol (PG).

* I discovered that having some metaborate dissolved in PG increases the solubility-limit of ascorbic acid.

* And I discovered that if one isn't careful, the solution of PG+metaborate+ascorbic can crystallize, causing the solution to separate into a cream and a liquid. It starts as smoke-like wisps, or cloudiness, or a few crystals appearing on the bottom. This can happen while mixing the concentrate hot, or it can start after a few days of sitting at room-temperature.

Here's a smattering of observations about crystallization:

1. It is not solely or even primarily a function of concentration-ratio (weight of powders in grams divided by final volume in ml). One solution with a ratio of 0.33 failed, and another with a ratio of 0.40 succeeded.

2. All solutions with a metaborate-ratio (weight of metaborate in grams divided by final volume in ml) exceeding 0.12 failed. None with less than 0.12 failed. Of two with ratios of exactly 0.12, one passed and one failed.

3. All solutions with a metaborate/ascorbic ratio of at least 0.533 failed. This ratio determines the alkalinity of the concentrate, and it appears that it dislikes alkalinity.

4. Phenidone and perhaps especially Dimezone S make the crystallization problem worse.

5. Higher temperatures while mixing ascorbic acid and Phenidone encourage crystallization during the mixing process.

6. Metaborate alone in PG will not crystallize. You need ascorbic acid in there.

That's what I know. Numbers 2 and 3 encourage one to reduce the metaborate, but if you do, you can't dissolve all the ascorbic acid in a reasonable time (or at all?). So there's a trade-off. In fact, it seems that there's a narrow zone where one can dissolve all the ascorbic acid while avoiding crystallization. And the developer D316 that I created back in January just happened to hit that zone. Alan Johnson, who named that developer after its posting-number, mixed the concentrate back then and has been testing it. I have a similar developer that's been sitting since then as a longevity-test. D316 is:

Propylene glycol .................... 16 ml (hot)
Sodium metaborate 4 mol ..... 2.2 g
Ascorbic acid ......................... 4.5 g
Phenidone ............................. 0.05 g
The result is almost exactly 20 ml of concentrate.
A litre of developer contains 20 ml of concentrate and 45 grams of sodium sulfite (but I'm thinking of boosting the sulfite).

I tried changing the amount of metaborate. At 2.0 g, I could not dissolve all the ascorbic acid. At 2.4 g, the solution crystallized while hot. That tells you how narrow the workable zone is. Also, D316 showed the beginning of crystallization when I mixed it too hot (around 90C), consistent with observation 5. Alan mixed his at 70C with no problem.

I posted this information so other home-brewers won't have to re-discover these things. I hope it helps somebody.

Mark Overton

Alan Johnson · Nov 10, 2012

In post 302 the formula has 2.7g metaborate so if 2.4 g crystallised I cannot figure out if post 302 formula would be OK.

albada · Nov 10, 2012

Alan Johnson said:
In post 302 the formula has 2.7g metaborate so if 2.4 g crystallised I cannot figure out if post 302 formula would be OK.

Post 302 crystallizes also. I ran strips with that baseline developer by mixing directly into water, but when I mixed it as a concentrate five days ago, it crystallized. Then I created more concentrates of various formulations, made a table of all concentrates I've ever mixed since January, and looked for patterns in the numbers. The result is yesterday's long posting, and the realization that D316 happened to hit the narrow usable window.

Mark Overton

Alan Johnson · Nov 10, 2012

I belive the sodium metaborate that Silverprint sell in the UK is the 8-mol aka Kodalk.This has more water in it and should be less prone to crystallisation than the 4-mol from the Formulary.
There is so much ascorbate in the concentrate it may still be resistant to aerial oxidation.

Progress on XTOL-concentrate

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