Progress on XTOL-concentrate

[albada]

Since the issue with water in your concentrate has been bugging you for many months now, some volunteer should finally set up a quantity of your concentrate, split it in half and mix one half with some amount of deionized water. With repeated activity tests every 1-3 months we could learn whether traces of water are likely going to reduce the shelf life of this concentrate.

Yes, that would be a good test.
Gerald Koch pointed out here that such chemicals will eventually dissolve at room-temperature. So the issue is the water that did not get steamed out.

Note that quite a few people will be reluctant to heat toxic and caustic chemicals close to 100°C, so it would be quite helpful to learn if a concentrate with reasonable shelf life could be made without steaming out the water.

The chemicals involved are:
* Propylene glycol, a food-additive (non-toxic).
* Sodium metaborate, slightly toxic, and at pH 10.5, not particularly caustic.
* Ascorbic acid (aka vitamin C), non-toxic, and at pH 3, not particularly acidic.
* Phenidone, almost non-toxic.

So getting the chemicals on you will be harmless. The temperatures involved are 85C at most, which is well below what's used for cooking. So there's a lower danger of scalding with D316 than with cooking. Also, D316 can be mixed at 65C (I've done it), reducing scald-risk even farther below cooking-risk.

Overall, I'd say mixing D316 is safer than cooking.

Mark Overton

[albada]

Tri-X developed in D316 for 12.75 minutes looks good. Here are the density-curves of D316 and XTOL:



Curves: In the graph, you can see that D316 is close to XTOL, but provides a little more linear gradation as you go from midtones into highlights.

Grain: In my loupes, grain of D316 ranges from same as XTOL to slightly better than XTOL, depending on density.

Sharpening: D316 sharpens Tri-X some, but clearly less than XTOL (sharpening of TMY-2 is about the same). If you want high sharpening, D316 with Tri-X is not for you. But lower sharpening is a benefit if the fringes (Mackie lines) from sharpening bother you.

Overall, I prefer D316 over XTOL due to its nicer grain and better linearity.

Mark Overton

[albada]

Neopan 400 works well with D316. Here are curves comparing it with Tri-X. Notice that Neopan 400 compresses highlights less than Tri-X.



Here are the films I've tested with D316 so far, along with their dev-times, which all happen to be a whole number of minutes:

Tmax-400 ........ 12
Tri-X ............... 13
Neopan 400 ...... 14
FP4+ ............... 16

I plan to test Tmax-100, Acros and most Ilford films, including Pan F+. Any other ideas?

Mark Overton

[Rudeofus]

I plan to test Tmax-100, Acros and most Ilford films, including Pan F+. Any other ideas?

I've tested Delta 3200 with D316 1+1 and negs look great, prints will follow soon. Dev time was 36 minutes (2 times Xtol times for Xtol 1+1 and Delta 3200). This test did not yield a characteristic curve or anything, but shows that higher dilutions of D316 seem feasible (Delta 3200 is usually quite demanding).

For those mixing fresh: you can use the easier to get Borax instead of Metaborate: replace 2.2 g of Sodium Metaborate Tetrahydrate with 2 g Borax and at the end of mixing adjust pH to 8.0 with Sodium Hydroxide (Sodium Carbonate should also work at this pH). Don't leave out the Propylene Glycol as it is said to influence the behavior of the Borate ion (and as a result buffering and pH).

[albada]

I've tested Delta 3200 with D316 1+1 and negs look great, prints will follow soon. Dev time was 36 minutes (2 times Xtol times for Xtol 1+1 and Delta 3200). This test did not yield a characteristic curve or anything, but shows that higher dilutions of D316 seem feasible (Delta 3200 is usually quite demanding).

For those mixing fresh: you can use the easier to get Borax instead of Metaborate: replace 2.2 g of Sodium Metaborate Tetrahydrate with 2 g Borax and at the end of mixing adjust pH to 8.0 with Sodium Hydroxide (Sodium Carbonate should also work at this pH). Don't leave out the Propylene Glycol as it is said to influence the behavior of the Borate ion (and as a result buffering and pH).

Wow! Thanks for doing this. It's good to know that it will perform well diluted 1+1. And I haven't tried Delta 3200 either, so that's another film to add to the known-to-work list.

For folks who wish to mix fresh (directly into water), the dev-times should be boosted by 10-15%. That's because a PG-concentrate develops faster than when mixed directly into water. Any idea why? Perhaps the esters formed in the concentrate don't dissociate when dissolved in water? Anyway, I notice that adding PG directly into water slows development, so you could try omitting the PG, resulting in this simple formula:

Sodium sulfite ........................... 45 g
Sodium metaborate dihydrate ...... 2.2 g (or 3.0 g of s.m. tetrahydrate)
Ascorbic acid ........................... 4.5 g
Phenidone ............................... 0.05 g

I developed a roll of Acros last night, which looks fine. I hope to take measurements this evening.

Mark Overton

[kb3lms]

Isn't PG a development accelerator? I know PPG and PEG are. Possibly when mixed in the concentrate it is combing with one of the other components so that it can get into the emulsion and act as an accelerator. But, when mixed directly into water it's ineffective. Just a guess.

-- Jason

[Photo Engineer]

Polyols are known, in generaal, as development accelerators and are used in emulsion coating as just that along for their other property of being humectants.

PE

[albada]

Polyols are known, in generaal, as development accelerators and are used in emulsion coating as just that along for their other property of being humectants. PE

The effect of PG on development-speed is interesting. Here are the times for D316 with TMY2:

Direct to water with No PG ......... 13 min (i.e., the formula I posted 3 postings ago)
Direct to water with PG ............. 13.75 min
PG-based concentrate ............... 12 min

So adding PG to water slows development, but when the PG is in a concentrate, it accelerates development. Weird, isn't it?

Mark Overton

[Photo Engineer]

I certainly cannot explain it.

PE

[Rudeofus]

So adding PG to water slows development, but when the PG is in a concentrate, it accelerates development. Weird, isn't it?

This is a wild guess but maybe it inspires more educated guesses: I have read it many times that PG forms an ester with the borate ion, and my little high school chemistry knowledge tells me that esters are more likely to form when water is forcibly removed. If all this is correct, I would assume that PG-Borate ester is formed in the concentrate version, which may have different properties from Borate and PG alone. It would be interesting to know whether different pH adjustments are needed with concentrate or fresh mix.

Since Mark observed that a given amount of PG has much more pronounced effect on small test clips than on whole rolls of film, it looks like PG somehow interacts with the gelatin or some other part of the emulsion.

PS: About the 1+1 dilution: I did an 120 roll in 500ml of developer, which means my results may or may not apply to 35mm rolls souped in 250ml.