Agitate › Dilution
Concentrate, water and the minimum
Film Developer Dilution Calculator
Rodinal at 1+100 in a 500 ml tank gives you 4.95 ml of concentrate. Against a 5 ml minimum that reads as a rounding error. The tank holds two films, so the real requirement is 10 ml and you are short by half.
The minimum is per film, not per tank
This is the calculation almost every other tool gets wrong, and the failure mode is quiet. A one percent shortfall looks like nothing. A fifty percent shortfall is a thin, uneven negative, and the number on the screen looked fine the whole time.
Agitate multiplies the maker's published minimum by the number of films in the tank, compares that against the concentrate your dilution actually produces, and blocks rather than nudges when the solution comes up short. Six of the developers in the bundled database carry a published minimum.
| Developer | Minimum per film |
|---|---|
| ADOX Rodinal and Adonal | 5 ml |
| Ilford Ilfotec HC | 5 ml |
| Ilford Ilfotec LC29 | 5 ml |
| Kodak HC-110 | 6 ml |
| Ilford Ilfosol 3 | 25 ml |
| Ilford Ilfotec DD-X | 60 ml |
Minimum concentrate per film, as published by the maker of each developer.
The tank is what decides the film count
Tank volumes are entered as their makers publish them, and each one carries the number of films it takes. That is the number the minimum is multiplied by.
| Volume | 35 mm films | 120 rolls |
|---|---|---|
| 300 ml | 1 | 0 |
| 500 ml | 2 | 1 |
| 900 ml | 3 | 2 |
| 1500 ml | 5 | 3 |
| 2500 ml | 8 | 5 |
The tank sizes offered in the app. A tank of your own volume can be entered as well.
Dilutions are written the way datasheets write them, as stock or as one part concentrate to so many parts water. The app reads 1+9 and 1:9 as the same thing, and returns nothing rather than guessing when a string is not a dilution at all.
Re-used developer needs more time, and the app adds it
The published remedy for a re-used working solution is ten percent of the developing time for each film already put through it, added linearly. Agitate applies that, tells you it has, and does not apply it to a one-shot dilution, where the bottle never sees a second film.
It also does not apply it to color. Stretching a color developer that way moves a bath meant to run to a defined point and shifts color balance rather than adding density, and color kits publish a capacity ladder instead of a percentage. Until such a ladder is in the database, a color time stays exactly as its maker published it. The expiry and capacity warnings still fire either way.
A half empty bottle keeps half as long
Air in the bottle is what kills a developer, so the shelf life you should count on for a half empty bottle is half the published one. That is how Agitate Pro's chemistry ledger works it out: the mixing date, the fill level and the number of films the bottle has already done, from which it produces the warnings before you pour rather than after.
Expired
Past its effective shelf life, counted from the mixing date and adjusted for the fill level. Blocking.
Nearly expired
Within two days of the end of its life, which is the point at which mixing fresh before you start is still an option.
Capacity exhausted
The bottle has already done as many films as it is rated for. Blocking, because more time will not fix an exhausted developer.
Below the minimum
Less concentrate in the tank than the maker requires for this many films. Blocking, with the required quantity named.
Every one of these warnings is in the free version. The ledger that tracks bottles over time is part of Agitate Pro, a one-time purchase, but nothing that tells you a run is about to go wrong sits behind it.
The check that catches a tank that looks fine
Concentrate and water for any dilution, the minimum counted per film, and the re-use surcharge applied only where it belongs.
Agitate for iPhone and iPad
Free, and every chemistry warning is in the free version.