Progress on XTOL-concentrate

albada · Jul 14, 2012

PeterB said:
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.

Peter, your posting prodded me to do the experiment below this evening, because it reminded me that I'm halfway through figuring out an exact clone of the XTOL that's now in production.

One difficulty is ascorbate is hard to find, so to clone XTOL, one must separately convert some ascorbic acid into ascorbate by adding sodium bicarbonate (baking soda). The problem with that is if the correct amounts of both ingredients are mixed, it will theoretically take a nearly infinite amount of time to convert all the ascorbic acid. To see why, suppose there is one molecule remaining of each ingredient. It will require perhaps years of stirring before those two molecules touch each other. So to complete the conversion in reasonable time, an excess of bicarbonate is needed. But what will that do to the developer?

So I developed one test-strip in XTOL, and a second in XTOL with 0.5 g/L of bicarbonate added. Their characteristic curves are virtually identical, and grain looks the same (but I didn't check sharpness). It appears that a small amount of bicarbonate won't hurt an XTOL-like developer, so it's feasible for home-brewers to create ascorbate this way. But I need to try the dev with and without DTPA to see if that makes any difference. Mytol dropped it, so I doubt it helps image-quality any.

Mark Overton

Kirk Keyes · Jul 14, 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.

Unless less the readings were made close in time to each other and you are skilled and experienced at making precise pH measurements and you have an electrode in excellent condition and calibration solutions that are fresh, I don't take much stock that there is a difference between two pH readings that differ by 0.03 pH units. If those readings were taken on different days, I'd say those readings are equivalent.

I've years of pH experience measuring everything from Deionized water to hazardous wastes, and pH can be a very tricky test for something that appears to be so simple. Something as simple as stirring can have great affect on some types of samples.

I've come to the conclusion that the whole number in a pH reading is pretty reliable. The first decimal can be accurate, but it is sometimes not very precise depending on the sample. The second digit has much less accuracy than the first, but it can be measured well if your setup is good and you have experience making those types of readings. The third digit in a pH reading, except in some special setups, can pretty much be used as a random number generator.

Don't get all uptight about a difference of 0.03 pH units!

albada · Jul 15, 2012

Order matters!

The order that ingredients are dissolved into a propylene glycol-based concentrate is important!
I made more concentrate today, and followed my formula in this order (at about 90C):

Order 1: propGlycol=24ml, s.metaborate=6.7g, ascorbicAcid=8.5g, dimezoneS=.2g

The clear liquid turned yellow upon adding the dimezone. Then it became cloudy, with lines of chemical-scale appearing on the bottom and sides of the beaker and growing. After a few more minutes, the bottom was almost entirely covered with scale. The solution ended up being thickly cloudy with what seems to be fine particles. And highly viscous.

This is similar to what happened in Feb 2012 after creating a highly concentrated concentrate. After a few days, some cloudy streaks appeared in it, and it became completely cloudy upon heating, and ended up looking like milk. Also highly viscous. Here's my posting about it from Feb 2012:
(there was a url link here which no longer exists)
My query is the sixth posting.

So I changed the order to this, completely dissolving each before adding the next: (still at about 90C)

Order 2: propGlycol=24ml, dimezoneS=.2g, s.metaborate=6.7g, ascorbicAcid=8.5g

I got the same behavior I mentioned a couple of days ago: The solution turned orange upon adding metaborate, and clear again upon adding ascorbic acid, and it fizzed upon adding the ascorbic acid, with visible foam.

With the clear-to-orange, and orange-to-clear, and fizzing, it's obvious that reactions are occurring in the propylene glycol solution in Order 2. Also, the yellowing and cloudiness and scale and high viscosity are different reactions occurring in Order 1.

Do the chemists here have any idea why dissolving the DimezoneS first versus last makes such a large difference?

Mark Overton

PS @Kirk: Okay, I won't bother if a pH-difference is small. One trick I use is to quickly go back and forth between my test-developer and XTOL (known to be 8.29). Think of it as a minute-by-minute calibration. I've been able to get repeatability within +/- 0.02 doing this. But getting that initial measurement of XTOL requires a real calibration, which one hopes will stay true for half an hour.

Kirk Keyes · Jul 15, 2012

With Order 2, when you say the solution turned orange, do you mean an orange precipitate formed, or merely that the solution color turned orange AND was still clear.

albada · Jul 15, 2012

Kirk Keyes said:
With Order 2, when you say the solution turned orange, do you mean an orange precipitate formed, or merely that the solution color turned orange AND was still clear.

The latter: The solution became orange colored, but remained clear with no cloudiness or precipitate. It looked like some drops of dye had been mixed in.

Note that Kodak's XTOL becomes light orange after mixing the first packet, and becomes clear after mixing the second packet.

Mark Overton

Relayer · Jul 15, 2012

Mark, first I'm note that your experiments is very interesting for me.

The solution turned orange upon adding metaborate,

metaborate is alkali. orange color because phenidone oxidized by metaborate

and clear again upon adding ascorbic acid, and it fizzed upon adding the ascorbic acid, with visible foam.

ascorbic acid with metaborate produce sodium ascorbate, which recover oxidized phenidone.

I don't understand why you need to mix metaborate with phenidone/ascorbic acid. Try to make concentrate as follow
part A: glycol+phenidone+ascorbic acid
part B: water+metaborate+sulfite

Kirk Keyes · Jul 15, 2012

I also agree that it's pain to dissolve inorganic compounds into organics.

The fizzing indicates that there is a bit of carbonate present and when you add the ascorbic acid, it's released from the solution.

Photo Engineer · Jul 15, 2012

Metaborate does not oxidize phenidone.

Phenidone is being oxidized and then is being reduced by ascorbate. This is often seen when mixing other developers and is why a pinch of sulfite is added. Doing that here woulb be a pain.

PE

albada · Jul 15, 2012

Success with Ilford HP5+

I've done all my testing with TMY2. This time, I wanted to compare this concentrate with XTOL using a film that was not made by Kodak, and not T-grain. And I wanted to test development of an entire roll, not just a short strip, to see if there is a capacity-issue. So I exposed and developed two 36-shot rolls of HP5+, and here are their curves:

They match nicely. That tells me that this concentrate can handle a variety of film-chemistries. Both rolls were developed identically: 220 ml of stock developer for 8 minutes at 20C (Ilford's recommendation).

Grain looks the same in my 22X loupes. I also took some tripod-shots outdoors, so you'll soon see some scans that'll let you gauge both grain and sharpness.

Mark Overton

EDIT: Evidently, the orange phenomenon described earlier is damaging the Dimezone S little, if at all. The concentrate is closely following XTOL, as it did when its ingredients were mixed directly into water (with my TMY2 tests).

Kirk Keyes · Jul 15, 2012

Make certain you do some push processing / N+ developments in your tests to make sure there's enough there to get the job done.

albada · Jul 16, 2012

Scans of photos

Here are full-resolution crops of HP5+ shot and developed identically in XTOL and the concentrate. XTOL is on the left; concentrate on the right.
XTOL:

Concentrate:

The scanner is a Nikon Coolscan IV-ED, which has a resolution of 2900 DPI on the negative.
What do you think of the grain and sharpness?

Also, I attached a down-scaled scan of the entire frame.

@Kirk: Push-developing is a good idea; I'll do that. I'll also do it diluted 1+1 to put even more stress on the developers.

Mark Overton

Murray Kelly · Jul 16, 2012

Nice work, Mark, and thank you for the hours in the basement!
The curious color changes seem to indicate there is enough water in the system to allow the phenidone to react. I note you heat the PG etc after mixing to remove any water. To exclude water in the PG (unlikely) and the metaborate could you not mix them first, then heat to dry out before adding the rest?

Just a thought.
Murray

Photo Engineer · Jul 16, 2012

Nice work Mark. I note that there is just a tad more grain in your developer. Do my eyes deceive me? The curves are certainly close though.

PE

albada · Jul 16, 2012

Michael R 1974 said:
To me it does look very slightly grainier but only in some tones. Also looks very slightly sharper but quite difficult to tell from scans. These differences could be entirely imagined, or real but trivial in practice. I would really need to see physical prints/negatives in order to finalize my subjective opinion.

Grain: I've compared on two monitors, both CRT and flat-screen, rapidly switching from one to the other. Flat-screen monitors are best for comparison because their focus doesn't vary, and grain is more conspicuous on them.
Anyway, I see some areas where grain is a hint worse; others where it's a hint better, such as the left house-window.
BTW, the scanner was manually focussed on one of the two house-windows.
The rolls are mostly identical frames, so I can scan more frames.

Sharpness: The photos were taken about 20 minutes apart, and the sun had moved a little, so deeper shadows on the tile roof might increase percieved sharpness in the concentrate. The sharpness of the other lines in the photos look the same to me.

Mark Overton

EDIT: On further critical exam, I notice that other lines are a bit sharper in the concentrate, such as the window-frames. I wonder if this is a focus-issue with the scanner (which would affect grain-perception), or if the concentrate is actually sharper. I'll definitely make some more scans.

albada · Jul 16, 2012

Storage in the refrigerator or freezer

I left the bottle of concentrate overnight in the refrigerator, and there is no precipitate on the bottom. I even put it in the freezer, and nothing precipitated out of solution. It simply became thick, like cool honey. This tells me that the concentrate can be refrigerated or frozen for storage, taken out only when needed.

Chemical reactions slow down with decreasing temperature. Would that mean the concentrate would last much longer if stored cold?

If so, perhaps it would last a decade or more in the freezer, or a few years in the refrigerator.

Mark Overton

albada · Jul 17, 2012

Here are more scans of XTOL and concentrate. These were saved at a higher JPEG-quality than my prior scans, so everything should be slightly crisper, hopefully making comparison easier. In these, I manually focussed the scanner on the rear window of the car.

Frame 15: XTOL:

Concen:

Frame 16: XTOL:

Concen:

Frame 17: XTOL:

Concen:

Can you see any consistent difference between the pairs?

Mark Overton

albada · Jul 17, 2012

While waiting for comments on the new scans above (hint hint), I figured I'd reply to some suggestions:

@Michael R: No, I have not checked higher densities yet. But I have the leaders of HP5+ from both rolls, so I can measure them tonight if I remember. I like your idea of developing an entire roll to D-max. Exposing such a roll will be easy: Just load it onto the reel in the light!

@Murray Kelly: I hadn't thought of adding metaborate first and then drying it before proceeding. That's an interesting idea and easy to test.

@relayer: Yes, a two-part developer could be made where part B is sulfite + metaborate. The problem is that part B can not be concentrated much due to the solubility limit of sulfite, so it will need a large container using much space, and it's likely to oxidize because it's aqueous. And it can not be stored in the refrigerator. So I prefer to keep the two parts as (1) concentrate and (2) sulfite powder, because both take little space and should store a long time in the refrigerator. Well, I *think* the concentrate will last long when refrigerated.

Mark Overton

EDIT: I just measured the leaders of the two test-rolls. XTOL is 2.40, and the concentrate is 2.39. Very close.

Kirk Keyes · Jul 18, 2012

I hope you're not storing your developer in your food refridgerator. It's just bad practice to mix the two - food and chemicals.

Relayer · Jul 18, 2012

albada said:
Yes, a two-part developer could be made where part B is sulfite + metaborate. The problem is that part B can not be concentrated much due to the solubility limit of sulfite

I have two suggestion
1) try to use Potassium Sulfite instead Sodium Sulfite
2) try to decrease amount of slfite to 30-40-50g/l

albada · Jul 18, 2012

Michael R 1974 said:
Hi Mark - regarding the most recent scans, I'm having a hard time finding any consistent differences one way or the other (essentially the same experience I had with the first scans). And I know your curves are essentially identical. My two cents: given the magnification, for practical purposes any differences in apparent graininess or sharpness between the concentrate and XTOL with this film are trivial.

Michael, thanks for responding! Your observations agree with mine, but I don't trust mine because I'm biased. At least with HP5+ and TMY2, this concentrate is achieving the goal of matching XTOL's grain, sharpness, curves and dev-times. But as a non-aqueous concentrate, it should last much longer. I'm encouraged, and will run more tests with it.

@Kirk Keyes - Well actually (swallowing hard), I do keep this in my food-refrigerator. Unless there are small children in a household, well-marked bottles of chemicals will never be accidentally ingested. And even if they were ingested, these chemicals are nearly non-toxic, so little harm would result. Some other chemicals, on the other hand...

@relayer - I like your ideas of potassium sulfite and reducing sulfite. In fact, I've tried both. This concentrate is intended to act exactly like XTOL, but I want to explore your ideas more to make developers that are different from XTOL. One reason I avoided potassium sulfite is I thought it was difficult to obtain; can you buy it in Ukraine?

Mark Overton

Relayer · Jul 18, 2012

albada said:
@relayer - I like your ideas of potassium sulfite and reducing sulfite. In fact, I've tried both. This concentrate is intended to act exactly like XTOL, but I want to explore your ideas more to make developers that are different from XTOL. One reason I avoided potassium sulfite is I thought it was difficult to obtain; can you buy it in Ukraine?

yes, I can buy it in Ukraine, but price is high. but I have other problem - sodium metaborate (kodalk) is very problematic to purchase in small quantity.
try 1st to reduce amount of sodium sulfite. may be this increase sharpness without dramatic increasing grain size.
here is my "clone" of XTOL:

RD-117 developer
Salicilyc acid 1g
Sodium sulfite 33g
Ascorbic acid 4.15g
Borax 8,5g
Phenidone 0.2g
Water 1l
pH 8.2

starting dev.time same as for D-76

kb3lms · Jul 18, 2012

Mark,

I don't see any differences between the XTOL and your concentrate. XTOL is my favorite developer and I am planning to try your concentrate since the concentrate would match up better with the volume of film I get to process. Really great stuff! Keep going!

-- Jason

albada · Jul 19, 2012

kb3lms said:
Mark, I don't see any differences between the XTOL and your concentrate. XTOL is my favorite developer and I am planning to try your concentrate since the concentrate would match up better with the volume of film I get to process. Really great stuff! Keep going!
-- Jason

Jason, thanks for the encouragement! I designed this concentrate for hobbyist-shooters like us who can't use even half of five litres of XTOL in six months.

A few days ago, I said that if Dimezone or Phenidone is mixed in last (instead of first), it starts a reaction that produces viscous cloudy liquid and scale on the beaker. Here's a photo of the scale. Everywhere the stirring rod rubbed the beaker, it started a reaction producing a line of scale.

I suspect the cloudiness and this scale are the same catalytic reaction. Have any of the chemists here seen anything like this?

Mark Overton

Photo Engineer · Jul 19, 2012

These are crystals formed by the stirring rod scratching a saturated mixture which then begins to form at the site of the scratch. It is well known to Organic Chemists that they must scratch some mixtures to begin precipitation or crystallization. As for why this forms in one case and not another, it may be due to a salt being formed in one that is not in the other.

BTW, very nice work on the concentrate. The results look great.

PE

Rudeofus · Jul 20, 2012

Relayer: You can make Kodalk yourself using (there was a url link here which no longer exists) (comes with great explanation! ). The recipe you posted contains salicylic acid which is a mild iron chelate, Ryuji Suzuki uses it in DS-10 to prevent iron catalyzed decomposition of ascorbate.

Mark: Two things.

If I compare Xtol to DS-10 in terms of usability, the biggest difference is that Xtol can develop slow films like PanF and TMAX, while DS-10 instructions recommend specifically against using DS-10 with these slow fine grained films. It would be very interesting how MOtol (your version of Xtol) copes with these films. Of course, there are more suitable devs for these slow films, but if one develops a few rolls a year (which is where your dev really shines! ) it may be nice to know that this dev also works for the rare roll of PanF+.
While deionized water is easy to get, it would be very nice if your dev could use tap water. Do you think you could add some sequestrants to your recipe? You don't have to worry much about iron with your concentrate, but calcium and magnesium should be taken care of. Calgon and Na2-EDTA should be easy to get, but they will change the pH and this must be accounted for.

Progress on XTOL-concentrate

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