Progress on XTOL-concentrate

[Gerald C Koch]

I remember reading of some exposed photographic plates that were discovered from a failed polar expedition. The plates were over 80 years old at the time of discovery yet produced usable images.

[albada]

I remember reading of some exposed photographic plates that were discovered from a failed polar expedition. The plates were over 80 years old at the time of discovery yet produced usable images.

Okay folks, I cut the roll into strips and froze them. Each strip is in a plastic film-can, and they're all in a metal cooking pot with a snugly fitting lid, providing two layers of shielding against light. Thanks for the ideas about this; ageing film is a variable that I don't need.

Here's an update of the baseline developer I posted a couple weeks ago. The new one litre formula:

Sodium sulfite ..................... 45 g
Sodium metaborate ............ 2.6 g
Ascorbic acid ...................... 4.5 g
Phenidone .......................... 0.05 g (I use a 2% solution of propylene glycol)

Target pH is 8.15. For TMY2: 12.25 minutes at 20C.

The only difference between this and the baseline dev of two weeks ago is metaborate went from 2.0 g to 2.6g, raising the pH to be closer to what XTOL uses. With the higher pH, there will be less risk of failure with films that dislike low pH.
Here are the curves for this developer and XTOL:



And here are crops of neg-scans:

XTOL: This dev:

The grain looks a bit finer in loupes, and the JPEG sizes are 1% smaller. But XTOL looks a hair sharper to me in those crops.

This dev is merely a stepping-stone. Things I plan to try are (1) reduce both metaborate and ascorbic acid to reduce concentration-ratio, (2) increase pH a little more to match XTOL, and (3) replace metaborate with TEA and replace Phenidone with Dimezone S to see if a concentrate based on TEA and Dimezone S will crystallize.

Mark Overton

EDIT: BTW, I didn't mean for this posting to sound closed to inputs from others. If you have any comments or ideas to try, I'd like to hear them.

[albada]

More questions for chemists (or those more knowledgeable about chemistry than I):

1. Will DTPA-Na5 (or pure DTPA) dissolve in an organic solvent such as propylene glycol or TEA? All the structures in DTPA-Na5 are carbon-based, so I'm guessing it will be soluble, but I'm not sure. Would you suggest a version of DTPA other than the pentasodium salt?

2. Is there any advantage of using DTPA over HEDP (aka "Dequest 2010" and "Etidronic acid")? Kodak uses DTPA heavily, but perhaps that's because it behaves better in powder form? For a concentrate, I won't care about that. Perhaps HEDP would be more effective?

I discovered that my developers that use 45 g/L of sulfite do not form a precipitate when refrigerated (unlike XTOL). That suggests a more convenient usage: Mix it one litre at a time, and store in the refrigerator (labeled clearly!). It should last three times as long in the fridge, compared with storing at room-temperature of 20C. And six times as long in the fridge compared with room-temp of 30C. But storage means the Fenton reaction with iron will be a problem, hence my interest in chelating agents.

TIA!

Mark Overton

[Gerald C Koch]

DTPA is soluble in organic solvents such as glycols. Kodak uses it in HC-110 which contains no water. The sodium salt is probablely not very soluble.

[eworkman]

I got two packs of the 5 liter yesterday from Freestyle.
I haven't really done darkwork for a year at least.
I note that packaging is new [relative, see above] and probably better.
A and B come in same size all plastic envelopes, rather than the film-on-paper of the past.
If I can keep struggling to motivation, I have some 8x10 HP5 to develop 1:2 etc in trays.
I've mixed the fix, and the materials and tools are awaiting in the sink.

[albada]

It's been two weeks, and I've run experiments changing the amount of ascorbic acid in the formula.

Here's an interesting observation. Pat Gainer's article here (http://unblinkingeye.com/Articles/Sy...synergism.html) on synergism has a graph that shows density versus ascorbic acid. It levels off when the ascorbic/phenidone ratio is 80. However, his test-developer was PC-TEA which contains no sulfite. If the developer has sulfite, the graph changes a little, as should be expected. With my developer, I found that activity levels off at a ratio of about 90.

XTOL, after converting chemicals into other equivalents, has a ratio of about 100. So I tried 100 in my dev, producing this formula:

Sodium sulfite ................ 45 g
Sodium metaborate ....... 3.1 g
Ascorbic acid ................. 5 g
Phenidone ..................... 0.05 g (in a 2% solution of PG)
pH = 8.16. For TMY2: 12.25 minutes at 20C.

The resulting H&D curve is an excellent match with XTOL:



The grain looks identical to me in both loupes and neg-scans. The JPEG file-sizes are equal, which objectively says the grain should be the same. Here are samples:

XTOL: Test-dev:

Notice the sharpening in both along the horizontal line near the bottom. Would you say they're sharpening the same amount? You can see the fringes (Mackie lines) from sharpening even in the thumbnails.

Anyway, I wanted to post this as a way of establishing another milestone that says "here is a developer that gives results practically identical to XTOL."

My next steps are (1) mix this as a concentrate in propylene glycol, and (2) add a chelating agent that can chelate iron. That chelating agent might be useful because I noticed that this developer is dilute enough that it does not form precipitate when stored in the refrigerator (unlike XTOL). That means you can store it in the fridge and it'll last three times as long. That got me thinking: You can make more than you need, and refrigerate the rest until it's all consumed.

Comments and ideas are encouraged as always.

Mark Overton

[albada]

In my posting yesterday, I forgot to say that my tests show that film-speed appears to drop a little when the ascorbicAcid/Phenidone ratio goes much over 100. Here's the curve I got when the ratio was 117:



Notice that the left 2/3 of the graph is slightly thinner than XTOL, but the right 1/3 is slightly denser. This means the neg has lower speed but higher contrast than XTOL (and same grain). The differences are small, though. Below a ratio of 90, activity begins dropping noticeably. So 90-100 seems to be the ideal range. It appears that the designers of XTOL made the ratio as large as possible so it could withstand as much ascorbate-loss as possible, but not so large as to lose speed.

I've also noticed that reducing the ratio appears to boost speed. The same seems to be true of reducing sodium sulfite. I say "appears to" and "seems" because I need to run more tests to verify these statements. Crawley's FX 55 developer was designed to achieve maximum speed, and claims a 1/2 to one stop speed-boost. Its equivalent ascorbicAcid/Phenidone ratio is only 11.6, and it has only 3.7 grams of sulfite, which seem to support my observations that low ratios of these chemicals give higher speed. Once I'm done with this XTOL-concentrate project, I'd like to experiment with speed-boosting developers.

Mark Overton

[Rudeofus]

In my opinion the difference in speed is barely visible, you seem to have a very flat optimum here. Since you did several test runs with different dev ratios, can you tell us from your data at which ratios you saw differences which would be more than let's say 1/3 stop or 0.1 density?

[kb3lms]

Great stuff, Mark! Keep going!

[Photo Engineer]

Mark;

If you repeated that experiment several times, I would guess that these differences would even out and the averages would be virtually identical.

One maxim I learned was "never do any experiment one time".

PE