Barry Thornton's two-bath question about time and temperature

What About Bob · Apr 28, 2024

Yesterday was the first time with using Barry Thornton's two-bath D-23 developer.

In my quest for an answer I have come upon the magic number of 68F/20C for temperature but today on my second test development run I was slightly over 70F/21C. The second set of negatives resembled that of the first set from last night. Some of the scenes were of high contrast and the highlight tones were brought down nicely and the frames made in the shade look good too.

How much tolerance is there with slightly higher temperatures when using two bath development? Would it be possible to use something like 72F/22C or slightly higher with some slight modification in time or does time matter that much? I understand that the development times in both baths are on the short end and I could be looking at around 60 to 90 seconds less, according the the MDC guide, and that grain might be an issue with using a higher temperature.

Also I know about the 125F51.3C for mixing of the developer but I wasn't sure if this same temperature also applied for mixing the metaborate solution. I was a little over 110F/43.3C when mixing Bath B.

Alex Benjamin · Apr 28, 2024

This is what Barry Thornton wrote regarding temperature:

The formulae given below allow one to process different makes and speeds of film together for very similar times, and you can use the same at a pinch and still get acceptable negs. They are not fussy about time and temperature within reasonable limits, they have outstanding capacity, they keep well, they are sharp and fine grained, and they are very low cost. All of these factors make two bath development attractive anyway, but they miss the main benefit.

I mix bath A at 100º F without problem. The important thing is the pinch of sodium sulfite before the metol, just like D-23. I use distilled water.

Bath B can be mixed at room temperature.

What About Bob · Apr 28, 2024

Thanks Alex

grahamp · Apr 29, 2024

Part A has a fairly shallow density curve, so it is not too sensitive to changes in time or temperature. Going much below 3 minutes is probably hard to get consistent, 4 min is probably easier. Part B should be used at, or very close to the temperature of part A, as should stop and fix.

Part B works with whatever developer is in the emulsion or left in the drained tank from part A. Extending time in part B has a limited effect - there is only so much developing agent carried over. Part B is just an alkali accelerator. Raising the temperature without changing the time should increase densities, but it will tend to depend on the film. You need to verify what works with your subjects.

I develop at 21C (70F), and would not worry at 23C (73F) with my subjects. Any higher and I'd run a test first.

Two bath developers in general do not work in quite the same way as single solutions. With single solutions, you have two variables, time and temperature, and the relationship is fairly linear at normal process temperatures. With two bath formulations you have to consider the effect of time and temperature on two related baths. Thornton's develops partially in part A, then uses the second alkali part to push the densities using the limited developing agent in a compensation effect. Even with constant temperature, you still have two time elements, so a simple time/temperature graph won't be reliable. And the time/temperature graphs are based on single solutions formulated for a useful image.

Thornton's Part A will give a decent negative, given time, though probably low contrast. Part B on its own won't develop at all, but will build on Part A's image using the residual chemistry.

What About Bob · Apr 29, 2024

Thanks grahamp

I am understanding the process more now.

I developed the first roll of Kentmere 100 for 4 minutes at 68F/20C and the second roll of Kentmere 400 for 5 minutes at a little over 70F/21C. Both sets of negatives look the same to me. After I developed that first roll I remembered a video that I saw that gave advice for using 4.5 minutes for medium speed film and 4 minutes for 50 speed. I thought to myself that I may have goofed but the negatives look and printed fine. Both films print actually quite well. I am really amazed at the print results especially with an added Multigrade 2.5 filter and also without a filter.

For Bath A I did 30 seconds with slow inversions and then 2 inversions every 30 seconds. For Bath B I did one inversion every minute. The inversion was very slow with a soft twist motion so as not to disrupt things too much. I was getting the feeling that if I overdid it with inverting Bath B too much that the embedded developer in the film could loosen out from the emulsion quicker. My mind is telling me this but maybe that isn't so? I was thinking to just let Bath B stand with no inversions. I read that with 35mm that may be a problem and can lead to bromide drag at the sprocket holes. I'm using 120. I kind of felt like Tom from Tom and Jerry when he found out that the white mouse was explosive and he ever so gently puts him down. In my case putting the tank, with Bath B in it, down and not touch it as much as possible, lol.

I am not sure if it is from the type of paper that I am using but the mid tones take on this somewhat metallicy but yet smooth appearance. I get this with the regular D-23 at 1:1 development but that result is more pronounced with using the two-bath development. I'm using Multitone RC pearl which I believe is by Inkpress, though the name isn't shown anywhere on the box and envelopes. This paper is naturally punchy, I had to alter a few things to get the contrast just right with working with this material. With using the two-bath development this seems to be proving good with this particular paper.

I switched to Multitone due to price. I am saving 2 to 2.3 times the amount of money for the same quantty of paper from the other brand that I was using. The goal is to keep doing more photography. It had taken some work and some wastage but I think I have things nailed down now and the results are starting to pay off.

After tonight I feel like it is 1992 all over again. First time doing darkroom work right after high school. Good times.

snusmumriken · Apr 29, 2024

FWIW, I always aim to use BT2B at 23 deg C. I don't know why, maybe because BT quoted that temperature somewhere? If my solutions are very cold, I'll use a water bath to warm them up (and the wash water, fixer and developing tank too). If only a couple of degrees out, I just use a time/temp chart to figure out a revised development time. Results are good, and grain is very unobtrusive, even with Eastman's old-tech Double-X in 35mm.

As regards agitation, I actually do continuous inversion agitation in Bath A (simply because I came to BT2B from Tetenal's 2-bath Emofin, for which that was the recommended routine), and in Bath B I do inversions at 30s, 1min, 2 min and 3 min. Again, that all works fine. Easy-printing negs, and no streamers with 35mm.

I think one can reasonably say that BT2B is a very forgiving process. So I would continue as you are, unless your negatives give you reason to make changes.

What About Bob · Apr 29, 2024

Thanks snusmumriken

I will do a few more tests with the higher temperatures. I will need to find a way to cool down the bathroom more. Temperature is now 79F26C! During the latter spring and summer my place becomes a heat trap.

Romanko · Apr 30, 2024

I learned about Barry Thornton's two bath developer from John Finch. There is a video on his Youtube channel (Pictorial Planet). More details can be found in his book "The Art of Black and White Developing" which I highly recommend. John recommends developing time of 4 to 5 minutes at 20 degrees C. Contrast can be regulated to some extend by increasing the frequency and length of agitation. Another tip is to change the concentration of metaborate in part B to 7 g to lower the contrast or to 20 g to increase it.

John also describes a method of push-development (=increasing contrast) by repeating the process several times. The film has to be thoroughly washed after each development to avoid contaminating bath A with bath B.

I used BT2B quite a lot and like this developer. It can be used with Kodak Technical Pan to tame its contrast.

gorbas · Apr 30, 2024

Please, don't go crazy with using bath B. After a few rolls you can easily develop whole film in only bath B. Carryover metol and sulphite from bath A stays active in B.
I was under impression that it gets spent/exhausted/neutralized in alkaline B, but it just sits there. I did tests a few years ago. You can develop film just in A, after 4min you will get thin negative that needs #4 or 5 grade paper, but totally usable. The same is with partially used B. Basically, to have "clean" 2 bath developing process, B should be one shot solution.
PS. for tests I used a 3-4 frames of 35mm film. Most likely it will be less developed if I used entire 36ex rolls.

snusmumriken · Apr 30, 2024

gorbas said:
Please, don't go crazy with using bath B. After a few rolls you can easily develop whole film in only bath B. Carryover metol and sulphite from bath A stays active in B.
I was under impression that it gets spent/exhausted/neutralized in alkaline B, but it just sits there. I did tests a few years ago. You can develop film just in A, after 4min you will get thin negative that needs #4 or 5 grade paper, but totally usable. The same is with partially used B. Basically, to have "clean" 2 bath developing process, B should be one shot solution.
PS. for tests I used a 3-4 frames of 35mm film. Most likely it will be less developed if I used entire 36ex rolls.

That's a really interesting observation, and it's going to make me change my habits.

I suppose one can get some measure of the carryover from the difference in volume between the two baths. If, after 15 films, bath A is 850 ml (my guess, based on experience), the carryover of metol into bath B could be 0.9375g in 1150 ml, which makes it about 13% the strength of bath A, or equivalent to using D-23 diluted 1+9 (roughly speaking). Presumably it won't actually be that strong, because some must be used up through development, and because some is lost through oxidation. It's the colour change cause by the latter that has generally prompted me to make a fresh bath B.

gorbas · Apr 30, 2024

Borax is cheap enough to do single use bath B, (but it's very mild alkali) and probably ideal for scenes under very contrast lighting, Kodalk is much more expensive. A few years back I had similar conversation with Raghu Kuvempunagar (is he also now MIA here?). He suggested me single use Bath B with Potassium Hydroxide bath from this thread: https://www.photrio.com/forum/threads/pyrocatechin-two-bath.36713/#post-529866. Now, I need to look at my notes what formula I did use at the end, but I remember nice results with beautiful, super sharp grain.

snusmumriken · Apr 30, 2024

gorbas said:
Borax is cheap enough to do single use bath B, (but it's very mild alkali) and probably ideal for scenes under very contrast lighting, Kodalk is much more expensive.

You don't need to buy Kodalk. 1.5g sodium hydroxide plus 7g borax produces Kodalk (sodium metaborate) in solution, equivalent to 10g Kodalk dry weight. See this thread: https://www.photrio.com/forum/threads/kodak-sodium-metaborate.186175/

grahamp · Apr 30, 2024

I use TTB in a Jobo, which probably negates some of the compensation effect, but it still handles highlights well, and that is rotary agitation all the way.

I find that carry over losses meant I had to make new solutions before I reached capacity. It is surprising how much solution can be retained in a tank and reel.

Barry (Thornton) suggested a sodium carbonate part B for higher contrast results. I have not needed it, and my one test seemed to increase density across the board, rather than steepen the curve. I'll try and dig out the reference. It should be in Elements or Edge of Darkness.

What About Bob · Apr 30, 2024

gorbas said:
Please, don't go crazy with using bath B. After a few rolls you can easily develop whole film in only bath B. Carryover metol and sulphite from bath A stays active in B.
I was under impression that it gets spent/exhausted/neutralized in alkaline B, but it just sits there. I did tests a few years ago. You can develop film just in A, after 4min you will get thin negative that needs #4 or 5 grade paper, but totally usable. The same is with partially used B. Basically, to have "clean" 2 bath developing process, B should be one shot solution.
PS. for tests I used a 3-4 frames of 35mm film. Most likely it will be less developed if I used entire 36ex rolls.

This had me thinking too. I like using solutions as one-shot even though it may be wasteful. Stop and fixer being an exception. There was one poster here who stated that he went as far as using his fixer only as one-shot to keep things fresh.

I have noticed that the Bath B solution starts turning a yellow tint and stinking a little after using it once. After the second time it stinks a little more and turns a little more yellow. I used the liter solutions only two times and then I dumped it.

The 15 roll max for a liter of solutions seems a bit of a stretch when I believe that after the third or fourth roll you would need to replenish the developer part. If you don't then the results go on the soft side due to weaker action of the developer and also with Bath B being overly concentrated with the carryover possibly throwing off the consistency. Then again if Bath A gets weaker and more carryover goes into Bath B then maybe this balances out the results?

gorbas · Apr 30, 2024

snusmumriken said:
You don't need to buy Kodalk. 1.5g sodium hydroxide plus 7g borax produces Kodalk (sodium metaborate) in solution, equivalent to 10g Kodalk dry weight. See this thread: https://www.photrio.com/forum/threads/kodak-sodium-metaborate.186175/

Thank you Jonathan! Very interesting thread!
Grahamp, as for carry over on the film and on the tank, from my days using Replenished D-76, 26 ml per roll was about right.

What About Bob · Apr 30, 2024

There is a 4 mol and an 8 mol. I have the 8 mol version of sodium metaborate. Is it the 4 or 8 that applies with the 12 grams for Bath B or does this even matter that much?

snusmumriken · May 1, 2024

What About Bob said:
The 15 roll max for a liter of solutions seems a bit of a stretch when I believe that after the third or fourth roll you would need to replenish the developer part. If you don't then the results go on the soft side due to weaker action of the developer and also with Bath B being overly concentrated with the carryover possibly throwing off the consistency. Then again if Bath A gets weaker and more carryover goes into Bath B then maybe this balances out the results?

Bath A won’t get weaker as a result of carry-over; it just gets smaller in volume.

snusmumriken · May 1, 2024

What About Bob said:
There is a 4 mol and an 8 mol. I have the 8 mol version of sodium metaborate. Is it the 4 or 8 that applies with the 12 grams for Bath B or does this even matter that much?

This is what Pat Gainer said about that here a while back:
"If you buy metaborate, don't be confused by the 4 mol-8 mol stuff. You would use the same weight of either in any formula. Sodium metaborate 8 mol has twice the molecular weight of the 4 mol. A certain weight of either one has the same number of molecules. One turns into the other at a certain temperature without any change in weight."

I don't quite understand that myself, because if the molecular weight is doubled, then the number of molecules per unit weight must be half, surely? But anyway, I don't buy metaborate, because it's hard to find here in the UK, and expensive when found, and can be made cheaply from (almost) household chemicals, as above (post #12).

What About Bob · May 1, 2024

snusmumriken said:
This is what Pat Gainer said about that here a while back:
"If you buy metaborate, don't be confused by the 4 mol-8 mol stuff. You would use the same weight of either in any formula. Sodium metaborate 8 mol has twice the molecular weight of the 4 mol. A certain weight of either one has the same number of molecules. One turns into the other at a certain temperature without any change in weight."

I don't quite understand that myself, because if the molecular weight is doubled, then the number of molecules per unit weight must be half, surely?

I'm trying to understand what Pat said as well. I have seen recipes where substituting a version of one chemical with another version, having different water weights in it or anhydrous, has a conversion factor. From what I have seen so far with the film and prints, the results are there and it works.

John mentions that D-23 retains its activity better than D-76 and that times are pretty much the same between the two developers. I have seen that mentioned once or twice here. Been using D-76 times from the MDC and other sites and all has been good. D-23 doesn't disappoint. I like John's videos. The first videos I remember viewing were from his Rodinal series.

retina_restoration · May 1, 2024

snusmumriken said:
Bath A won’t get weaker as a result of carry-over; it just gets smaller in volume.

There's no reason not to use Bath A for at least 5-10 rolls of film before making fresh. However, Bath B should only be used 3 or 4 times before making a new bath, for the reasons stated (Bath B becomes more and more active as Bath A is carried over).

Alex Benjamin · May 1, 2024

retina_restoration said:
However, Bath B should only be used 3 or 4 times before making a new bath, for the reasons stated (Bath B becomes more and more active as Bath A is carried over).

Interesting. Had not read that info elsewhere. The fact that bath B can be made at room temperature makes it easier to change.

retina_restoration · May 1, 2024

Alex Benjamin said:
Interesting. Had not read that info elsewhere. The fact that bath B can be made at room temperature makes it easier to change.

Easier still is to maker up a gallon jug of B, and just use what you need once and toss it when you're done.

markbau · May 1, 2024

Romanko said:
I learned about Barry Thornton's two bath developer from John Finch. There is a video on his Youtube channel (Pictorial Planet). More details can be found in his book "The Art of Black and White Developing" which I highly recommend. John recommends developing time of 4 to 5 minutes at 20 degrees C. Contrast can be regulated to some extend by increasing the frequency and length of agitation. Another tip is to change the concentration of metaborate in part B to 7 g to lower the contrast or to 20 g to increase it.

John also describes a method of push-development (=increasing contrast) by repeating the process several times. The film has to be thoroughly washed after each development to avoid contaminating bath A with bath B.

I used BT2B quite a lot and like this developer. It can be used with Kodak Technical Pan to tame its contrast.

I used Finch's recommendation, FP4, 5 mins in each, the negs were way undeveloped. Don't think I'll bother with it again, happy back with D 23. I used to like Finch but lately he seems to be making videos for the sake of making videos with questionable content.

retina_restoration · May 1, 2024

markbau said:
I used Finch's recommendation, FP4, 5 mins in each, the negs were way undeveloped. Don't think I'll bother with it again, happy back with D 23. I used to like Finch but lately he seems to be making videos for the sake of making videos with questionable content.

At 5 minutes in both Am and B, there's no way you should have ended up with underdeveloped negs. Five minutes in each is quite a lot for FP4. I suspect your chemistry may have been faulty (or you underexposed the film?).

Disconnekt · May 1, 2024

I know @Andrew O'Neill uses BT 2-bath dev, maybe he can drop in & give some tips on it?

Barry Thornton's two-bath question about time and temperature

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