Progress on XTOL-concentrate

albada · Jul 8, 2012

Although I've been quiet for weeks, I've still been busy trying to create a concentrated version of XTOL that will keep for years. I think I'm close. Below is the graph of true XTOL versus my test-dev (TMY2, 6.5 min at 20C):

As you can see, the two curves are so close that they appear to be one curve in the thumbnail. And careful exam in my 22X loupes shows the grain is the same too. Here's the formula:

Propylene glycol .................... 24 ml
Sodium metaborate 4 mol ..... 6.7 g
Ascorbic acid ......................... 8.5 g
DimezoneS/Phenidone .......... 0.2 / 0.105 g
Propylene glycol to ................ 33.3 ml (final volume)
(heat to 90C to dissolve everything and drive out the water in the metaborate)
To make one litre of developer, mix 33.3 ml of concentrate into water containing 90 grams of sodium sulfite. That's 1+29 dilution.

So far, I've tested this by mixing the ingredients directly into water; I haven't actually made any concentrate yet. That's the next step.

Chemists will be interested in the latest weird problem I had:
Adding the propylene glycol to that developer drops the pH by .07 and raises the temperature by 1 degree C. So it appears to react with something. Adding PG to XTOL does not change its pH, and the only thing my dev has that XTOL lacks is ascorbic acid, so I'm guessing that AA reacts with PG. The dev works fine anyway, but I had to remove a little acid and add a little alkali to correct the pH. PG is not as inert as I thought. Do the chemists here have any idea what's happening?

Mark Overton

yeknom02 · Jul 8, 2012

Speaking of the older thread, can someone link to it? I'd be interested to read what's been going on until now.

albada · Jul 8, 2012

Responding to both questions:

@Michael R 1974: I used ascorbic acid instead of isoascorbate because ascorbic acid is easy to obtain. You can even buy it at health food stores, whereas isoascorbate was not even sold by Photo Formulary the last time I checked.

@yeknom02: Here's the link to the long DS-10 thread:
(there was a url link here which no longer exists)
This is basically all my questions, answers and discussion about developers and my unexpected experiences with them as I was learning about the topic. Home-brewing developers is full of surprises. Several knowledgeable people contributed much good information in that thread, so it's worth reading.

Mark Overton

albada · Jul 9, 2012

By the way, here's a trick I've been using to develop short test-strips uniformly with a small amount of developer. I hold a strip to the bottom of a stainless steel tank using hobby-magnets. Here's a photo of a strip after fixing:

Be sure the emulsion is facing up! The magnets don't rust, so they should not cause iron-contamination. But they stick poorly to the tank, so there are four more magnets under the bottom of the tank to hold those inside-magnets in place (8 magnets total). I develop in a water-bath to hold temperature to within .1 or perhaps .2 degree C, agitating with inversions. I use 100 ml of developer, but 50 ml would probably work also. I'm getting good consistency with this set-up, so I figured I'd share it with other experimenters.

Mark Overton

Rudeofus · Jul 9, 2012

albada said:
Chemists will be interested in the latest weird problem I had:
Adding the propylene glycol to that developer drops the pH by .07 and raises the temperature by 1 degree C. So it appears to react with something.

Propylene glycol is a weak acid which may lower your pH to some extent. A rise temperature may or may not indicate a chemical reaction in the most narrow sense, think about dissolving sodium thiosulfate in water.

albada said:
Adding PG to XTOL does not change its pH, and the only thing my dev has that XTOL lacks is ascorbic acid, so I'm guessing that AA reacts with PG.

XTOL may be much more buffered than your dilute soup. Which brings up an interesting point: Can you see a difference in edge definition between XTOL and your soup?

@Michael: I have no idea why people would recommend sodium ascorbate instead of ascorbic acid, when the latter one is so easy to obtain from any third rate pharmacy.

Alan Johnson · Jul 9, 2012

PG may also change dissociation:
Dead Link Removed
What is the pH of this developer and the development time in the dilute solution?

albada · Jul 9, 2012

Alan Johnson said:
PG may also change dissociation:
Dead Link Removed
What is the pH of this developer and the development time in the dilute solution?

@Rudeofus: The buffering should be similar to or even better than XTOL, because the AA will improve buffering some and I'm using more metaborate. However, I wrongly thought that PG was neutral. I gotta check these things in the CRC Handbook.

@Alan: The pH (with the PG mixed in) is 8.33, which is .04 higher than the 8.29 I measured for XTOL. The dev-times are intended to be the same as XTOL. I used 6.5 min @ 20C for TMY2. That article about differing dissociation-constants is interesting. Thanks for pointing that out.

Mark Overton

Rudeofus · Jul 9, 2012

albada said:
@Rudeofus: The buffering should be similar to or even better than XTOL, because the AA will improve buffering some and I'm using more metaborate.

I'm not sure how you arrive at this conclusion. Xtol uses about 100g powder per 1l of regular soup, while your soup uses about 15 g/l, so even diluted Xtol has more powder per liter. I don't know the composition of Xtol but would assume that some of that amount of powder helps buffering. AA has pKa values of 4.1 and 11.8, which will not help buffering around pH of 8.3.

Photo Engineer · Jul 9, 2012

Adding plain alcohol to water will raise the temperature. So, PG and water does not surprise me.

Good work Mark. I am waiting to see the sharpness and grain. We can see the grain from an enlarged scan of your step wedge.

PE

BetterSense · Jul 9, 2012

This is very interesting. I like Xtol a lot for the shadow speed and grain that it gives, but I've been worried that it's a proprietary formula and I won't always be able to get it.

This has the added benefit of being liquid, which is more convenient to me. If I can get an HC110-like developer that is just like Xtol--wow!

Gerald C Koch · Jul 9, 2012

Proprietary formula? The origin of Xtol is described in detail in "The Genesis of Xtol," by Dick Dickerson and Silvia Zawadski (Photo Techniques Magazine, Vol. 20, No. 5, 1999, p. 62 ff). The article also includes the formula.

albada · Jul 9, 2012

Gerald C Koch said:
Proprietary formula? The origin of Xtol is described in detail in "The Genesis of Xtol," by Dick Dickerson and Silvia Zawadski (Photo Techniques Magazine, Vol. 20, No. 5, 1999, p. 62 ff). The article also includes the formula.

@Rudeofus: My formula requires that 90 g/L of sodium sulfite be mixed in separately from the concentrate. That makes it a little more hassle than HC-110, but it also means it gains the buffering and other benefits from the sulfite.

@BetterSense: My motive for creating this concentrate is to have something that will last for a few years. After mixing, XTOL lasts 6 months according to Kodak, and I can't use 5 litres in that time. So this concentrate is intended for people who shoot 2 rolls per month or less as a hobby. Those who shoot 3 rolls per month or more will be able to use all 5 litres of XTOL (undiluted) in 6 months. But for low volume shooters, the extra few minutes it takes to measure two things (sulfite and concentrate) is not a problem.

@PE: Thanks for the encouragement, and the note about alcohol. From prior tests with similar formulas, I believe sharpness will equal XTOL. But I'll certainly run sharpness tests with the actual concentrate. For now, grain is the main thing I'm watching, while keeping development-times identical to XTOL.

@Gerald: Do you know if the formula from that article matches the patent? I have the patent, but haven't been able to locate that article. If you have access to that article, can you post the formula?

Mark Overton

Gerald C Koch · Jul 9, 2012

Mark,

I have the magazines but unfortunately they are not readily available. At one time the article was on the magazine's website but when they started stressing digital they removed it. I stumbled on the article on the web a couple of years ago. Nothing ever gets removed from the web. Have you checked the APUG archives? IIRC, if not identical they were very similar except for the patent formula being divided for packaging.

Jerry

Photo Engineer · Jul 9, 2012

Bill Troop and Steve Anchell have published the XTOL formula as stated in the patent, and the patent (according to Bill) matches the patent.

I discussed this with Bill just a few hours back.

PE

albada · Jul 10, 2012

Photo Engineer said:
Bill Troop and Steve Anchell have published the XTOL formula as stated in the patent, and the patent (according to Bill) matches the patent.
I discussed this with Bill just a few hours back.
PE

@Gerald: I did some searching a few months ago, and came up dry. Maybe I'll try again with archive.org or whatever it's called and see if they have it.

@PE: I weighed the two packets from my latest XTOL-purchase, and did some reverse-engineering to reconcile those measurements and the MSDS-ranges and the patent. My conclusion is that the sulfite was reduced slightly and redistributed, resulting in this:

Dry packet A:
Sodium sulfite ...................... 44.7 g (MSDS=44.9..)
DTPA ................................ 1 g (from patent)
Sodium metaborate (8 mol) ..... 4 g (from patent) (MSDS=2.6..5.2)
Dimezone S ..................... 0.2 g (from patent)
Total = 49.9

Dry packet B:
Sodium sulfite ................. 37.9 g (MSDS=37.4..40.05)
Sodium metabisulfite .......... 3.5 g (from patent) (MSDS=2.67..5.34g)
Sodium isoascorbate ........... 12 g (from patent) (MSDS=8.01..13.33g)
Total = 53.4

I'd also like to re-check this formula by mixing it and comparing pH's with XTOL, and comparing density-curves. But that will mean buying some DTPA, which I don't yet have. I'm suspicious because the pH in the patent is 8.20, but the latest and prior XTOL-batches I've purchased measured 8.29 and 8.26 with a calibrated meter. That makes me suspect the metabisulfite was reduced and/or metaborate was boosted.

Mark Overton

Photo Engineer · Jul 10, 2012

USP 5756271 gives a close approximation to XTOL, the main differences being in the tweaks for manufacturing. Bill assures me, that after talking to the inventors, it is the exact formula.

Comparison of this formula with what is posted above should give us a good comparison between the two and see what is changed or not changed.

You can find the formula in the patent or in Anchell and Troop, p 49.

PE

Rudeofus · Jul 10, 2012

Michael R 1974 said:
Another good example is Microdol-X. We know there was some kind of anti-silvering agent in there, but it is a trade secret. Why then, can't we just look up the patent?

You mean this one?

Photo Engineer · Jul 10, 2012

Proprietary ingredients in the Microdol family are not listed in patents. There are patents to bar use and proprietary components that are kept secret.

PE

albada · Jul 13, 2012

The concentrate works! Here are the two curves of XTOL versus concentrate:

As you can see, they're about the same as mixing ingredients separately, and the dev closely follows XTOL. Grain is the same. So dissolving everything into propylene glycol didn't hurt anything, despite a little scare I had when the liquid turned orange and clear again because I dissolved things in a different order. I suggest following the order below:

Propylene glycol .................... 25 ml
Sodium metaborate 4 mol ..... 6.7 g (dissolves in about 3 minutes)
Ascorbic acid ......................... 8.5 g (dissolves in 7-10 minutes)
DimezoneS/Phenidone .......... 0.2 / 0.105 g (dissolves instantly if ground in mortar-and-pestle)
Propylene glycol to ................ 33.3 ml (final volume)

Heat to 90C to dissolve everything and drive the water out of the metaborate.
To make one litre of developer, mix 33.3 ml of concentrate into water containing 90 grams of sodium sulfite. That's 1+29 dilution.
Times are same as XTOL. Target pH is 8.33.

The only change to the formula above was to start with 25 ml of PG instead of 24 because the powders expand the liquid less than I expected, so you can start with a bit more.

Whew! This has been a long project, and I still need to run tests on sharpness and different kinds of film. But this is looking good.

@Alan Johnson: This concentrate is similar to D316, except for adding more metaborate to boost pH. So the keeping-test you're doing will be helpful for this as well.

Mark Overton

PeterB · Jul 13, 2012

albada said:
I'm suspicious because the pH in the patent is 8.20, but the latest and prior XTOL-batches I've purchased measured 8.29 and 8.26 with a calibrated meter. That makes me suspect the metabisulfite was reduced and/or metaborate was boosted.

You might not be as far out as you think, the patent for XTOL lists the final pH as 8.20+/-0.05 which takes into account all the variations in the ingredients and the mixing process they considered at the time. You have done very well to get so close and it may not make any practical difference to the grain, sharpness or the characteristic curve.

Alan Johnson · Jul 13, 2012

As far as I know there is no standard test for developer keeping properties.It seems to depend on the volume of air in the bottle compared to the volume of developer and how often the bottle is opened.
My test has about 20% developer concentrate 80% air and the bottle is opened to air about once a month.

Photo Engineer · Jul 13, 2012

There is an open tray keeping test for developers that we used at EK. I have reported this elsewhere on APUG.

Place 1 L of developer in a standard 8x10 tray. Develop a step wedge in it. Cover with a plastic lid. Keep for 24, 48, etc hours and retest. The change in the curve will show keeping and capacity if done with the proper procedures.

PE

BetterSense · Jul 13, 2012

Your curve only seems to go up to 1.5, which is what, 5 stops? Why not take it out to 3.0?

albada · Jul 13, 2012

BetterSense said:
Your curve only seems to go up to 1.5, which is what, 5 stops? Why not take it out to 3.0?

That's the range of the 21-step Stouffer wedge I have. The 21 steps of 1/3-stop each covers a 7 stop range, which compresses to about 5 stops on the film due to the gamma of 0.6. I set the exposure to clip the beginning of the toe (left side of my curve doesn't start flat), but that's still not enough range to see where the film starts shouldering-off. Oh well, that's the best I can do.

Mark Overton

Photo Engineer · Jul 13, 2012

You need a wedge with 0.3 (one stop) density changes for this job. You can get them from Stouffers.

PE

Progress on XTOL-concentrate

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