How many rolls can you develop with CineStill Cs41?
CineStill's product page says the quart kit is reusable for up to 24 rolls (1000 mL), or 12 rolls for the 500 mL kit. For each roll already developed, add 2% to the developer time. The instructions PDF lists a smaller number for fresh solution: 8 rolls of 135-36 or 120 per quart, 4 per pint.
Two figures, two meanings
The instructions (rev. 9/26) have a capacity chart for working solutions: 960 mL (32 oz) takes 8 rolls of 135-36 or 120, 480 mL takes 4, 240 mL takes 2. That is the number of films CineStill recommends you can reliably process in one batch of solution. The same sheet says you can process 25%, 50% or more rolls than the chart lists if you are willing to judge the results yourself, by combining used developer with unused developer to make up the full volume and adding time. Its advice is to process film until you no longer like the results, and to do it within a few days of mixing.
So 24 per quart is a ceiling for kit use with the time increase, and 8 per quart is the chart for fresh solution. For the reuse calculator, 24 matches the product page and 8 matches the chart. Pick the one you trust more; the calculator warns you when your roll number goes past it.
One difference between the sources: the product page gives +2% per roll for both sizes. The PDF gives +4% for a pint (+2% for a quart, +0.5% for a gallon). I show both in the table below.
Developer time for each roll
The table starts from 3:30 with fresh developer, the 3.5 minutes at 102 °F that CineStill uses in its own example. Your base time may differ (temperature, push or pull), so enter yours in the reuse calculator, which uses the same sums. Roll 24 comes to 5:07 (+46%); in a pint at 4%, roll 12 comes to 5:02 (+44%).
| Roll | Added (+2%/roll) | Quart, +2% | Pint, +4% (PDF) |
|---|---|---|---|
| 1 | +0% | 3:30 | 3:30 |
| 2 | +2% | 3:34 | 3:38 |
| 3 | +4% | 3:38 | 3:47 |
| 4 | +6% | 3:43 | 3:55 |
| 5 | +8% | 3:47 | 4:04 |
| 6 | +10% | 3:51 | 4:12 |
| 7 | +12% | 3:55 | 4:20 |
| 8 | +14% | 3:59 | 4:29 |
| 9 | +16% | 4:04 | 4:37 |
| 10 | +18% | 4:08 | 4:46 |
| 11 | +20% | 4:12 | 4:54 |
| 12 | +22% | 4:16 | 5:02 |
| 13 | +24% | 4:20 | n/a |
| 14 | +26% | 4:25 | n/a |
| 15 | +28% | 4:29 | n/a |
| 16 | +30% | 4:33 | n/a |
| 17 | +32% | 4:37 | n/a |
| 18 | +34% | 4:41 | n/a |
| 19 | +36% | 4:46 | n/a |
| 20 | +38% | 4:50 | n/a |
| 21 | +40% | 4:54 | n/a |
| 22 | +42% | 4:58 | n/a |
| 23 | +44% | 5:02 | n/a |
| 24 | +46% | 5:07 | n/a |
Pint column stops at 12, the product page's limit for 500 mL. Times are mm:ss, rounded to the second.
What limits the blix
The time increase applies to the developer only. The product page says the mixed blix clears at least 24 rolls of color negative film and that you do not need to lengthen the blix time as you continue to use it. The PDF agrees: reusing the blix does not affect the processing time. Neither source gives a separate blix limit for the 500 mL kit.
The developer is the part that weakens. CineStill's instructions say results are best when the chemicals are used once, that remixing developer is not recommended for push processing, and that it is less effective at lower temperatures. Contamination also shortens life: the PDF warns that a few drops of blix or soap can ruin the developer.
Do the sums for your roll
The reuse calculator opens here with the quart rule (3:30, +2%, 24 rolls) and roll 9 entered. Change the roll number, base time or capacity and it gives the time and the rolls left. Two rolls in one tank count as two. CineStill's example time is at 102 °F; for another temperature see the temperature calculator, and for black-and-white developers that are mixed fresh each time, the dilution calculator.