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

joho · Feb 4, 2025

Just my 2cents on a two bath developer, Once used a kodak 2.bath that was used for B/W Cine films [machine developed] - used that for daily newspaper output 50 years ago.
it was simple .
NOTE: temp at 28-32clsius &&&time was at a 45- to 65 sec. each bath - BUT!!! film can not be outside it is rated ASA !!!
no pre-wash neened SO it was 60 sec A ---it was 60 sec B .... stop... fix ....wash dry 10 to 14min done....

retina_restoration · Feb 4, 2025

John Wiegerink said:
I'm a little curious about trying to push film in a 2-bath developer like 2-bath D-23 or even BTTB. I just don't think those developers would lend themselves to do a good healthy push on Tri-X or HP5+. If you extend your times in bath A it's more like using just a normal developer. A more potent bath B would help the push some, but would it really be enough? Of course, I'm referring to 2-bath developers that really aren't true 2-bath developers. I'd go with just a developer that is normally used for pushing, which most single bath developers will do. Oh, and I'm not curious enough to experiment with a 2-bath developer for pushing myself and will leave that to other folks here.

Agreed. A divided developer like BTTB is not the right choice for "pushing" film, since its inherent property is a reduction in film speed by about one full stop (with many films). So, if you choose a divided developer, you're already at a disadvantage and you're fighting with it to get it to do something it's not made to do.
As I said earlier, use D-23 at a high dilution and a long development time and it will have the effect of increasing film speed.

snusmumriken · Feb 4, 2025

retina_restoration said:
A divided developer like BTTB is not the right choice for "pushing" film, since its inherent property is a reduction in film speed by about one full stop (with many films).

I agree about BT2B being a poor choice for pushing, but what makes you say that speed loss is an inherent property? I’m willing to bet you are basing that statement on more experience and deeper insight than I have; but I have to say, I don’t notice any loss of speed (relative to box speed) with 35mm Delta 100, FP4+, HP5+; and anyway from what theory I have read, I would expect development of exposed silver grains to be initiated just the same as in any developer. Metol has the reputation of being good at that anyway.

Alex Benjamin · Feb 4, 2025

retina_restoration said:
A divided developer like BTTB is not the right choice for "pushing" film, since its inherent property is a reduction in film speed by about one full stop (with many films).

snusmumriken said:
what makes you say that speed loss is an inherent property?

I have the same question. In The Film Development Cookbook, Anchell and Troop state the opposite about two-bath developers in general. Quote:

Two-bath can be used for virtually all films exept document films. Since time is fixed, develoment is automatic, typically resulting in:

normal emulsion speed, or slightly higher

good acutance with moderately fine grain

long scale gradation, with some highlight compensation...

good economy

They don't mention BTTB, but do mention other variations of the D-23 two-baths, including Stoeckler, which is close to BTTB. If true that these allow full emulsion speed, is there something in Thornton's formula that works in the opposite direction? Or are Troop and Anchell wrong about this?

Milpool · Feb 4, 2025

I’m not into two-solution development for my own pictures but besides using a special purpose high speed/low contrast developer, two-solution would be the best way to push since you can get maximum emulsion speed without high contrast. If you want more speed than a single cycle gives you, repeat. The formula could be optimized for lower fog as well.

There is nothing special about Thornton’s version which would underperform other metol-sulfite two-solution approaches when it comes to emulsion speed. In fact his formula is only trivially different than any number of others including Adams (divided D-23), Stoeckler fine grain etc.

retina_restoration · Feb 4, 2025

Alex Benjamin said:
I have the same question. In The Film Development Cookbook, Anchell and Troop state the opposite about two-bath developers in general. Quote:

They don't mention BTTB, but do mention other variations of the D-23 two-baths, including Stoeckler, which is close to BTTB. If true that these allow full emulsion speed, is there something in Thornton's formula that works in the opposite direction? Or are Troop and Anchell wrong about this?

In my experience, my best negatives made using BTTB were the ones that received 1/2 to 1 stop more exposure than I normally would have given. BTTB negs are always thinner than with any other process.

Chuck_P · Feb 4, 2025

Alex Benjamin said:
They don't mention BTTB, but do mention other variations of the D-23 two-baths, including Stoeckler, which is close to BTTB. If true that these allow full emulsion speed, is there something in Thornton's formula that works in the opposite direction? Or are Troop and Anchell wrong about this?

With TMX I had a whopping 1 2/3 stop loss from the box speed. I've been currently rating it at EI32 but I'm certainly pleased with the pictorial results so far. So I would be curious to the answer to your question as well.

Alex Benjamin · Feb 4, 2025

Chuck_P said:
With TMX I had a whopping 1 2/3 stop loss from the box speed. I've been currently rating it at EI32 but I'm certainly pleased with the pictorial results so far. So I would be curious to the answer to your question as well.

Maybe @Steve Anchell could chime in?

snusmumriken · Feb 5, 2025

retina_restoration said:
BTTB negs are always thinner than with any other process.

Several points here, from my experience. If you over-develop in BT2B, you end up with unprintably dense negatives, as with any other developer. Don’t ask me how I know. Otherwise, my BT2B negatives do perhaps look slightly thinner than in other developers that I used in the past; but they definitely don’t have less shadow detail, while they do have highlights that print straight or almost so on grade 2 or thereabouts. In general, denser negatives are also grainier, so avoiding excessive density is a benefit, IMHO.

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

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