Why not 2 baths developer only?

Sidd · Friday at 12:00 PM

What I have read and heard till now that 2 bath b&w negative developers have many advantages over conventional single bath ones. Like, they are temparature and film independent, very good for highligh control, usually maintain and sometimes increase film speed, keep for long time etc.

My question is, if 2 bath developers are so good, then why do we use conventional single bath developers at all?

retina_restoration · Friday at 12:35 PM

Sidd said:
What I have read and heard till now that 2 bath b&w negative developers have many advantages over conventional single bath ones. Like, they are temparature and film independent, very good for highligh control, usually maintain and sometimes increase film speed, keep for long time etc.

My question is, if 2 bath developers are so good, then why do we use conventional single bath developers at all?

2 bath developers are NOT temperature independent. You can vary the temperature of the two baths somewhat, but if you work at 85F (or 60F) then you are most definitely going to change the results. Many two part (divided) developers use a Bath A that is a functional developer on its own. For example, Barry Thornton's version of Divided D-23 has a Bath A that is nearly identical to regular D-23 and it acts as a rather slow developer, without the use of Bath B. So if you are using a divided developer of this type and you deviate significantly from 68F, you're going to have an effect on the outcome.

I've found that 2 bath developers rarely deliver full emulsion speed. I prefer Thornton's version myself, but it always requires 1/2 to 1 full stop more exposure to get negatives I want. Karl Matthias's "2B-1" is better at enhancing film speed, sometimes giving an extra half stop of speed, depending on the film you choose.

Divided developers aren't more popular because they require making from scratch from chemicals that not everyone cares to acquire and keep in their darkroom (takes up space, tedious to weigh out and assemble). It also adds another step in the process, and many people barely have the patience for standard "develop/stop/fix" protocols, let alone adding another step.

Andrew O'Neill · Friday at 12:55 PM

Trickier to use the Zone System.

Paul Howell · Friday at 1:13 PM

Thorton provides directions use as both a single bath and divided. I just finished my last batches of Diafine, very old still in cans. It was ok, but limited how I developed a negative as I was limited to a single ISO for each roll or sheet of film. As noted by Andew O"Neill expansion and contraction is much more limited. I found that Diafine held shadows very well, and provides a fine gained negative at the expense of edge sharpness. Most modern films can be shot at box speed or a bit above. the excpection is Tgain films which have very thin emulsions which cannot soake up much of the A solution, I had to shoot Tmax 3200 at 800. On the side of the coin, usable at any temp from 70 to 90, (at least Diafine) 3 mint A, then 3 mints B, water rinse, fix and done. In the 70s and 80s when a working PJ I carried a quart kit of Diafine, a packet of fixer, and small bottle of a wetting agent for emerancy use in the feild.

John Wiegerink · Friday at 3:44 PM

Divided developer are not bad at all and some folks would be better off using a 2-Bath developer instead of trying to play Ansel Adams the Zone master. I use Barry Thornton's 2-B, but have two different B baths. One bath B is with Sodium metaborate and the second is with sodium carbonate. You could use several bath B's for different results. You could use borax, sodium metaborate, sodium carbonate or even sodium or potassium hydroxide for different levels of PH in bath B. One nice thing about two bath developers is that they aren't real fussy on time and temp, which makes them very friendly for beginners.

dcy · Friday at 3:45 PM

Sidd said:
What I have read and heard till now that 2 bath b&w negative developers have many advantages over conventional single bath ones. Like, they are temparature and film independent, very good for highligh control, usually maintain and sometimes increase film speed, keep for long time etc.

My question is, if 2 bath developers are so good, then why do we use conventional single bath developers at all?

I have tried Barry Thornton's Two Bath. My view is that "it's fine". I was neither dazzled nor disappointed. This is the first time I hear that a 2 bath increases film speed. I cannot see why that would be the case, and it's certainly not something I've noticed. I did a side by side comparison of various developers, and, if anything, the film I developed with BTTB seemed to either need more exposure or more development in order to match the negatives I got with D-23, D-76, and PC-TEA.

retina_restoration said:
Divided developers aren't more popular because they require making from scratch from chemicals that not everyone cares to acquire and keep in their darkroom (takes up space, tedious to weigh out and assemble). It also adds another step in the process, and many people barely have the patience for standard "develop/stop/fix" protocols, let alone adding another step.

I suspect that this is the main reason. My impression is that most people buy developers commercially. I like to make film developer, but as a point of comparison, I stopped making paper developer for the time being and switched to commercial ones. I suspect that most film photographers enjoy playing with chemistry less than I do.

Paul Howell · Friday at 4:11 PM

You can make a version of divided D76, standard formula for D76, just keep the borax out of solution A and mix with cold water to make 1 quart for solution B. I would go 4 mint A and 4 mints B, like any divided developer do not use an acid stop. I would start with box speed then adjust as needed.

ags2mikon · Friday at 4:25 PM

I used diafine in the early 1970"s and again in the late 90s and early 2000's and found it will in fact develop negatives and some film worked very good in it. Pan F, Plus X, Tri X were some of the best I tried. Foma 100, APX 100 and FP-4+ were not bad. I gave up on making T-max work in it. The formula did change over the decades, and so did the film. It is also expensive too. There are formulas out there for it or at least close to it. I was given what was supposed to be the formula from the 70's by a man in LA decades ago. Did it work? It did. Man did it have a lot of crap in it. I use D-23 1:1 and have been for the last 10 years. It works a lot like Perceptol (highlights) with better shadow speed. To each his own poison.

JerseyDoug · Friday at 4:40 PM

Life is so much simpler with a liquid one-shot developer.

Paul Howell · Friday at 4:43 PM

Yeah, Diafine along with Acufine and Edwal is now part of Omega Brands, not sure if Omega makes it or has it made by Photosystem. I had a few quart kits in cans that I mixed up, a 1 gallon kit now runs around $90 a gallon. It is easy to replenish and you can run a lot of film in a gallon kit.

Sidd · 2025-08-16T00:49:28-0400

Thank you all for sharing your thoughts and experiences on the topic, however, it would be interesting to know your thoughts on the image quality aspects of 2 bath developers more thoroughly.

F4U · 2025-08-16T01:29:35-0400

Sidd said:
What I have read and heard till now that 2 bath b&w negative developers have many advantages over conventional single bath ones. Like, they are temparature and film independent, very good for highligh control, usually maintain and sometimes increase film speed, keep for long time etc.

My question is, if 2 bath developers are so good, then why do we use conventional single bath developers at all?

Because before most of us were born, Eastman Kodak Company spent more money than most countries' GDP on R&D to market the finest and most consistent quality products the world ever has known or ever will. All you needed was a bottle, some clean water, a thermometer, and follow the instructions as they wrote them. Tiny nuanced results from other products and experiments can't top that to any remarkable degree.

albireo · 2025-08-16T06:54:08-0400

JerseyDoug said:
Life is so much simpler with a liquid one-shot developer.

I'm a late convert, but poor, unfashionable, humble HC110 diluted B or E does so much really well.

And I've yet to find a developer that makes Fomapan 100 sing like Rodinal 1:50 regularly inverted does.

halfaman · 2025-08-16T07:28:07-0400

Sidd said:
What I have read and heard till now that 2 bath b&w negative developers have many advantages over conventional single bath ones. Like, they are temparature and film independent, very good for highligh control, usually maintain and sometimes increase film speed, keep for long time etc.

My question is, if 2 bath developers are so good, then why do we use conventional single bath developers at all?

I recall what PE said about developers: there is no magic bullet. Two baths developers work great with some films under certain conditions, and the opposite with others. Just like any other developer.

For me, I am not interested in adding an additional developing step and will keep using single solution developers.

retina_restoration · 2025-08-16T09:21:58-0400

Sidd said:
Thank you all for sharing your thoughts and experiences on the topic, however, it would be interesting to know your thoughts on the image quality aspects of 2 bath developers more thoroughly.

It’s been said before, and I’ll repeat it: there is no “magic bullet” developer. The image characteristics are baked into the film and your development technique has a limited effect on the result.

I will also say that your choice of film will determine how much a divided developer will affect the negatives. Old style, thicker emulsions will respond better to a divided developer and modern films like Tmax will be far less affected. (Which is not to say that Tmax isn’t going to look good in a divided developer- I often use BTTB with Tmax films and like the result. But as far as I can tell, any developer works well with Tmax films)
Fomapan 400 works very well with BTTB and other two bath developers. So does Tri-X.

What is the visual effect on films when using a two bath developer? In general, it suppresses runaway highlights, preserves good shadow detail, and improves value separation throughout the tonal scale. It seems to suppress undesirable grain characteristics like clumpy, coarse, hard grain. It can be very effective in managing inherently contrasty films - I’ve used it with Ferraria Orto and it did a good job of reigning in the contrast.

But it’s not going to make a great image out of a badly lit scene, or severely under/overexposed film. It’s not magic, but it can be a useful tool in your kit, if you take the time to understand and it and use it wisely.

Ultimately, it’s up to you to try it first yourself to see if it’s a useful tool. I recommend doing technical testing to compare two or more developers on the same film/image. IE: shoot a bunch of frames of the same scene and cut the film up and process the pieces in the developers you want to compare.

juan · 2025-08-16T09:39:52-0400

In my area I have extreme contrast ranges - SBR 10 and above. For roll film I found that exposing for the shadows and using divided developer usually works best. The divided developer with minimal agitation takes care of the highlights.

John Wiegerink · 2025-08-16T09:42:51-0400

Well said Paul and a very good explanation of the benefits of BTTB. Maybe most of the negativity or poo-poo about a good 2-bath developer comes from Zonies who are just jealous on how easy it is to get a very good full tonal range negative from a simple 2-bath developer. I bet some of the Zonies who knock 2-Bath developing have never even tried it for themselves. That said, I'm a XT-3(Xtol) replenish and Pyrocat freak with a little BTTB thrown in.

Paul Howell · 2025-08-16T11:38:45-0400

Not all divided developers are alike. Thorton's version is very different from Diafine, which is different from divided D76. Thorton is a edge type higher in acuance, Diafine is fine grain, lower in contrast, while divided D76 is likely somewhere in between. When grain is not an issue such as LF or even 6X9 then Thortons', 35mm or 1/2 frame Diafine, my guess is that divided D76 will work with most formats but not be the best for 1/4 frame. If all else fails, test and go forth.

retina_restoration · 2025-08-16T12:00:59-0400

Sidd did not specify which specific divided developers he was contemplating. Relatively few of us are familiar with or use Diafaine, myself included, so I stuck to discussing BTTB. Divided D-76 is similar, but I expect most people considering adopting a divided developer are more likely to choose the simplest of them, and BTTB is high on the list of simple but very useful 2 bath developers.

And yes — test for yourself and see what you like.

Paul Howell · 2025-08-16T12:18:10-0400

Folks in the past have posted what they think is the formula for Diafine, but divided D76 is likely the simplist to make or buy from PF, which also sells a couple of Thortons developers along with their version of ILford ID 3 which can be used as a single or two bath developer. Freestyle has Diafine in the gallon size, now $96. + shipping. I would start with PF version of divided D76.

bluechromis · 2025-08-16T12:40:52-0400

Jay Defher says that two bath developers are good for mystery films, such as exposed film found in an old camera.

bluechromis · 2025-08-16T13:27:13-0400

I'm not sure that the argument, "I don't want to complicate things and have another bottle to store, etc," is such a compelling argument against two-baths. How much of this really represents, "I like how I am doing things and don't want to change."

There are a number of home-mixed divided developers that use a part B containing only one ingredient. Presumably, the dry chemical could be pre-measured and made into packets to be mixed up for one developing session. That doesn't seem so hard.

If one prioritizes simplifying chemistry to the greatest extent, there is an argument for using a monobath.

As said, two-baths complicate chemistry somewhat, but simplify other things such as not having to be so obsessive about exposure, development temp, etc.

The needs of a beginner can be different than those of an expert user. The need to avoid failures and the disappointment they bring is more important for a beginner, and divided developers can be more forgiving. Beginners may be trying out different types of film for the first time, and divided developers can accommodate that.

Milpool · 2025-08-16T13:31:15-0400

Thornton is only trivially different than the plain old Adams divided D-23 and others such as Stoeckler so no new ground was broken there.

You’re quite right they are different than “true” two bath developers (Diafine being an example). Researchers at Kodak did do work on these things but the formulas were never commercialized as far as I know and were generally considered to be compromises.

To answer OP’s question, since most two-solution developers are based on solvent formulas, what you can generally expect versus a single bath solvent developer are:

-Reduced solvent effects
-A slightly more linear characteristic curve
-Potential to retain emulsion speed with lower contrast
-In some cases possibly enhanced edge effects
-Increased risk of non-uniformity with roll films

Like any other deviation from standard processing, two-solution development is a little different and involves compromises. What you gain on some characteristic you lose somewhere else.

Paul Howell said:
Not all divided developers are alike. Thorton's version is very different from Diafine, which is different from divided D76. Thorton is a edge type higher in acuance, Diafine is fine grain, lower in contrast, while divided D76 is likely somewhere in between. When grain is not an issue such as LF or even 6X9 then Thortons', 35mm or 1/2 frame Diafine, my guess is that divided D76 will work with most formats but not be the best for 1/4 frame. If all else fails, test and go forth.

Sidd · 2025-08-16T14:16:47-0400

Milpool said:
Thornton is only trivially different than the plain old Adams divided D-23 and others such as Stoeckler so no new ground was broken there.

You’re quite right they are different than “true” two bath developers (Diafine being an example). Researchers at Kodak did do work on these things but the formulas were never commercialized as far as I know and were generally considered to be compromises.

To answer OP’s question, since most two-solution developers are based on solvent formulas, what you can generally expect versus a single bath solvent developer are:

-Reduced solvent effects
-A slightly more linear characteristic curve
-Potential to retain emulsion speed with lower contrast
-In some cases possibly enhanced edge effects
-Increased risk of non-uniformity with roll films

Like any other deviation from standard processing, two-solution development is a little different and involves compromises. What you gain on some characteristic you lose somewhere else.

Thank you for summarising the benefits of 2 baths developers, however, your last point "increased risk of non-uniformity with roll films" confused me. I thought, from my readings on the subject, that 2 baths developers are meant to be used with non-uniformly exposed negatives!

Sidd · 2025-08-16T14:20:59-0400

retina_restoration said:
It’s been said before, and I’ll repeat it: there is no “magic bullet” developer. The image characteristics are baked into the film and your development technique has a limited effect on the result.

I will also say that your choice of film will determine how much a divided developer will affect the negatives. Old style, thicker emulsions will respond better to a divided developer and modern films like Tmax will be far less affected. (Which is not to say that Tmax isn’t going to look good in a divided developer- I often use BTTB with Tmax films and like the result. But as far as I can tell, any developer works well with Tmax films)
Fomapan 400 works very well with BTTB and other two bath developers. So does Tri-X.

What is the visual effect on films when using a two bath developer? In general, it suppresses runaway highlights, preserves good shadow detail, and improves value separation throughout the tonal scale. It seems to suppress undesirable grain characteristics like clumpy, coarse, hard grain. It can be very effective in managing inherently contrasty films - I’ve used it with Ferraria Orto and it did a good job of reigning in the contrast.

But it’s not going to make a great image out of a badly lit scene, or severely under/overexposed film. It’s not magic, but it can be a useful tool in your kit, if you take the time to understand and it and use it wisely.

Ultimately, it’s up to you to try it first yourself to see if it’s a useful tool. I recommend doing technical testing to compare two or more developers on the same film/image. IE: shoot a bunch of frames of the same scene and cut the film up and process the pieces in the developers you want to compare.

Your elaborated comment is very helpful.

Why not 2 baths developer only?

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