Monobath developers compared: Df96, Kentmere and more

A monobath is a black and white developer and fixer in one solution. One bath replaces the developer, stop bath and fixer: you pour it in, agitate for a few minutes, pour it back into the bottle and wash the film. CineStill Df96 and Kentmere Monobath both work at room temperature and process about 16 rolls per litre, but you give up some control over contrast and film speed.

What a monobath is

Normal black and white processing has three baths because developer and fixer do opposite jobs. The developer turns the exposed silver halide crystals into black silver. The fixer dissolves the crystals that are left, so the film stops reacting to light.

A monobath does both at once, so the two reactions race. The developer has to finish its work on the exposed crystals before the fixer dissolves them. When the fixer wins, development stops, however long the film stays in the bath. That is why monobath times are minimums: CineStill says you can extend the Df96 time to make sure the film is fully fixed, and the extra time does not add development.

Two things tip the race:

• Temperature. Heat speeds up the developer. CineStill pushes and pulls Df96 by temperature alone, and Harman says a 6 °C change moves the speed of its Kentmere monobath by about one stop.
• Agitation. Agitation speeds up the fixer. Harman warns that too much agitation raises the fixing rate and lowers the apparent film speed. CineStill puts it the same way: development goes up with temperature and down with agitation.

How to use a monobath developer

Follow the sheet for your monobath. The sequence is the same for all of them:

1. Bring the bath to temperature. Harman’s Kentmere monobath runs at 21 °C. CineStill Df96 works from 20 to 28 °C, with a different time and agitation pattern at each temperature.
2. Load the tank as for any black and white film, in a changing bag. Develop black and white film at home covers the equipment and the loading.
3. Pre-wash only if your sheet says so. FPP asks for a water pre-wash at the bath temperature. Harman and CineStill do not mention one.
4. Pour in the monobath and start the timer. Agitate exactly as the sheet says. For the Kentmere monobath: four inversions in the first 10 seconds, then two inversions every minute. Tap the tank on the bench to knock air bubbles off the film.
5. Pour it back into its bottle when the time ends. Write the roll count on the label: the time grows with every roll.
6. Wash. Harman gives 5 to 10 minutes in running water, or the fill-and-invert method: 5, then 10, then 20 inversions, with fresh water each time. CineStill gives 5 minutes in running water, or at least 10 fills and drains.
7. Rinse in wetting agent and dry as usual. Dry film without water spots covers the last step.

If the film comes out milky, it is not fully fixed. With Df96, CineStill says to put it back in the monobath for longer. ars-imago recommends a short bath in normal fixer. CineStill also notes that films such as T-Max and Delta can come out with a pink or purple dye that fades.

The monobaths compared

Values come from each maker’s own instructions. Check the sheet that comes with your bottle, because makers revise them.

Monobath	Form	Time and temperature	Capacity per litre	Notes
CineStill Df96	Ready-to-use liquid (1000 ml or 530 ml), or powder that makes 1000 ml	6 min at 21 °C, 4 min at 24 °C, or 3 min at 27 °C, each with its own agitation pattern. All minimum times	16 or more rolls. Add 15 s for each roll already processed, up to 8 min	Works from 20 to 28 °C. Change the temperature by 6 °C per stop to push or pull. Tabular-grain films need double the time
Kentmere Monobath Film Developer (Harman)	Ready-to-use liquid, 1 litre	6 min 15 s at 21 °C	16 rolls of 135-36 or 120, or 23 of 135-24. Add 15 s per roll, up to 10 min for the 16th	Box speed at 21 °C on Kentmere Pan 100, 200 and 400 and Ilford Pan F+, FP4+, HP5+ and SFX 200. Plus or minus 2 °C moves the speed by about ⅓ stop. Delta films need longer
FPP Super Monobath	Ready-to-use liquid, 1 litre	5.5 min at 68 °F (20 °C) or 3.5 min at 75 °F (24 °C)	About 15 rolls of 35mm	Pre-wash first. Not recommended for films faster than ISO 400. T-Max films need longer
ars-imago MB	Liquid in two parts, A and B, mixed in equal amounts	8 min at 20 to 25 °C. Or dilute 1+1 with water for one-shot use, 10 min	Up to 15 films	Best with cubic-grain films. Not recommended for tabular-grain films such as Delta and T-Max. Suggests a second fixing bath for archival negatives
FF No.1 (Famous Format)	Liquid concentrate, 250 ml, mixed 1+3 with distilled water	6 min at 21 to 22 °C	10 rolls of 35mm, 12 of 120, or 20 sheets of 4x5	Inversion agitation. The maker’s website no longer loads, so check that you can still buy it

FPP’s page gives its temperatures as “75 degrees” and “68 degrees” without a unit. They can only be Fahrenheit, so the Celsius values in the table are conversions.

Kentmere Monobath is Harman’s entry. Its data sheet, code F26, went up on the Ilford site in June 2026. It narrows the process on purpose: one temperature, one agitation pattern, one time, and a short list of films that reach box speed. That makes it the easiest to get right on the first roll, if you shoot one of those films.

CineStill Df96 is the most flexible, with a rating chart for dozens of films and three temperature and agitation pairs to fit your room.

Pros and cons

What you gain:

• One bottle and one step. No stop bath, no fixer, no mix-ups between bottles.
• Forgiving timing. Once the film is fixed, extra minutes do not change the development.
• Room temperature. All five work at about 20 to 24 °C, so you rarely need a water bath.
• Reuse. One litre covers 15 or 16 rolls for four of these five, which suits occasional developing.
• Speed and space. With Df96 or the Kentmere monobath, process and wash take less than 20 minutes.

What you give up:

• Control over contrast. You cannot shorten or lengthen development to soften or harden the negative. Temperature is the only real lever, and it moves speed and contrast together.
• Speed on some films. CineStill’s own chart rates Kentmere 400 at ISO 250 to 400 in Df96, and Rollei Retro 80S at ISO 25. Harman gives box speed for its monobath only on the films it lists; other films need longer times.
• Film choice. Tabular-grain films such as Ilford Delta and Kodak T-Max need longer times in Df96 and in the Kentmere monobath, and ars-imago does not recommend them at all.
• A time that changes. The time grows as the bath ages, so you track the roll count.
• Agitation sensitivity. Too much agitation lowers the speed. Too little lets bromide drag lines form: CineStill warns against leaving the tank still for more than a minute.

Temperature, time and reuse

Pick one temperature and stay with it. Above 28 °C, CineStill says you get pushed negatives with more density and grain, and below 20 °C pulled ones.

For reuse, follow the time increase in the table and keep a tally on the bottle. CineStill gives Df96 a shelf life of 1 year from purchase, and says to use it up within 2 months once opened. Harman gives 12 months for an unopened bottle and 2 months for used solution.

Check that your monobath still works

• Colour. Df96 turns yellow, then dark amber as it wears out. Some colour change is normal for other monobaths too: ars-imago says the residue that forms at the bottom of the bottle does not affect results if you do not pour it into the tank.
• Snip test. CineStill suggests one before each reuse: put a light-struck piece of film leader in a cup of the monobath. It should turn opaque black. If it comes out thin, warm the bath and test again. If it stays clear, the bath is exhausted.
• Thin negatives. A run of thin negatives from correctly exposed film means the bath is tired, too cold, or both. Thin and dense negatives shows how to get the most from the ones you already have.

Why the app is called Monobath. A monobath replaces the developer, the stop bath and the fixer with one solution. The app does the same for conversion: like a monobath, you will not need anything else.

Sources

• CineStill: Df96 monobath product page
• CineStill: Df96 processing instructions (PDF)
• Harman: Kentmere Monobath Film Developer data sheet, F26 (PDF)
• Film Photography Project: FPP Super Monobath
• ars-imago: MB Monobath data sheet (PDF, copy hosted by Maco)
• Famous Format: FF No.1 concentrate directions for use (PDF, copy hosted by Freestyle)