That's a good point about XTOL-clones already being available. I wonder how much testing they've been through?
Originally Posted by polyglot
Anyway, you might want to store those 15 bags in the freezer. I don't know what their shelf-life at room-temperature is, but it's probably under a decade.
Testing is an interesting topic. I've been thinking of the kinds of tests I'll want to run my concentrate through. These include:
- Aging in various storage-conditions (hot humid areas are probably the worst).
- Tolerance to errors in measurements by users.
- Water types: hard, soft, well, softened.
- Film types: PanF on the slow side, to Delta 1000/P3200.
- Temperatures: 18C to 28C should cover the range.
- Pulling and especially pushing.
- Dilutions, although this dev is more dilute than most so we might not want to dilute it any more.
Each test would need to be a full roll to check capacity, and compare grain/density/sharpness with XTOL.
Any other tests that should be done?
Dilutions are often used to control both the shape of the curve/contrast and sharpness. Many people use XTOL at 1+1, for example. 1+3 can be useful too. So you might need to test the "capacity" of your developer's basic stock solution. ie how many ml of the stock solution are needed to develop a roll of film (~80sq. inches). I may have mentioned this before but perhaps some type of test in which you determine the minimum quantity of stock solution needed to develop an entire role to "D-Max" at the development time you have been using to plot normal contrast. I put "D-Max" in quotations because it is not likely the film's actual D-Max. So maybe a reasonable test could be:
1. For a given film, determine the highest density you get in your single-frame tests with normal development time (may require some alterations to your standard testing since you are not currently plotting the full curve). Maybe instead of plotting a curve you just give one frame "full exposure", develop for the normal time, and measure the transmission density.
2. Give an entire roll the same exposure as in (1) with normal development and measure the resulting density. This would have to be repeated with decreasing amounts of stock developer until a decrease in density is observed.
Another series of tests that could potentially be worthwhile would be "pressure tests" on agitation frequency. How tolerant is this developer to decreased or increased (ie Jobo) agitation frequency before getting uneven development and/or streaking?
Take this for what it's worth though, Mark. I'm not exactly in PE's league when it comes to this stuff. I'm just raising a few points that neurotic people like me would think about before using a developer (in addition to the other tests you listed).
I had not thought of this. Maybe I could expose a whole roll by loading a reel in the light, but that would not imitate actual usage. Maybe take pictures of the light-table or northern sky to get a controlled dense exposure? Anyway, yes, minimum solution needed would be a good thing to check. I'll think more about how to do this. I suspect the dev-times will increase disproportionately (due to greater exhaustion) as the volume of solution drops, so it'll take multiple attempts (at one roll a pop) to dial-in the correct time. The result would be a few points on an exhaustion-curve, and then we would pick the cut-off point.
Originally Posted by Michael R 1974
Mark, there is a test for this using small quantities of film. It uses standard clips of 35mm film.
as per the listed formuls how doesonemeasure .05 g in the real world??
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that's measure .05 gram phenidone....
Peter, use a dilute solution of Phenidone and add it as needed.
As I mentioned last week, I'm trying variations of a baseline developer. Here are six developers I recently tested:
Sodium sulfite ............... 35, 40, 45, 47.5, 50, 55 g
Sodium metaborate ...... 2.4, 2.2, 2.0, 1.9, 1.8, 1.6 g
Ascorbic acid ................ 4.5 g
Phenidone .................... 0.05 g
Propylene glycol ........... 15.5 ml (includes %-solution for Phenidone)
pH = 8.02 for all of these.
All were developed to the same contrast (slope) as stock XTOL for TMY2.
The experiment was to see what effect various levels of sulfite had, keeping pH constant. I'll identify each developer by its sulfite content (e.g., "the 40 developer").
The grain looks identical for the 40 through 55 developers, and is a hint better than XTOL. Grain is a hint coarser than XTOL for the 35 developer. The lower sulfite developers might be a tad sharper than the highest sulfite developers.
The dev-times were: 15.3, 14.25, 14.1, 14.0, 13.83, 13.58 minutes. Here's a graph of those dev-times:
The pH is constant, so the time-differences are solely due to the synergistic effect of sulfite on the developer. Notice that dev-time shoots up when sulfite drops below 40.
Here's the most interesting graph. This shows loss of true speed (Y-axis) versus sulfite-content (X-axis):
For each developer, I calculated the difference in EI (i.e., effective film-speed) using speed-points determined by densities of .1 above B+F and .2 above B+F, and calculated the loss of speed compared with XTOL. I averaged the number-pairs to help smooth the results, resulting in this chart.
Yes, XTOL is always faster than these developers, I suspect because it uses DimezoneS instead of Phenidone. But the loss is insignificant up to 45 -- only 0.08 stops of speed lost; that's only 1/12th of a stop. But above 45, the loss shoots up. So adding sulfite over 45 reduces true speed and gains nothing that I can see.
Evaluating trade-offs: There's no advantage in going above 45; all that does is reduce speed and possibly sharpness. And 35 gives worse grain with an insignificant speed-boost (and longer dev-time). That leaves 40 and 45. Suppose the user of this developer is not accurate in measuring sulfite. Then selecting 40 means risking thin neg's if too little sulfite is supplied. OTOH, 45 is more tolerant of too little, but risks a small speed-loss if too much sulfite is supplied. However, in this case the higher pH will partly compensate by increasing density. So the risk of disappointment is lower with 45 than 40. So I think 45 wins. That happens to be the baseline developer I described here: http://www.apug.org/forums/viewpost.php?p=1388724.
Any comments about all this?
I'm thinking of boosting metaborate to boost pH and see what happens. The low pH of 8.0 concerns me because DS-10 had trouble with some slow films, and its pH was 8.0, which might be the cause. The amount of ascorbic acid seems a little high, as the ascorbic/phenidone ratio is 90. Gainer's graph leveled off at 80. That suggests either decreasing my ascorbic acid or increasing the phenidone. Any suggestions about other variations to try?
first let me express my amazement and my gratitude that you go through all this effort and document not only the final results but also all these important intermediate steps which got you there. There are two variations to this experiment which would interest me personally and which might be of interest to others:
- Effect of using Borax instead of Metaborate. The latter one is more difficult to get and with a pH of around 8 Borax should be more than alkaline enough to work. It will take a tad more Borax than Metaborate which means we will get better buffering, which in turn means possibly reduced sharpness. Since we turn a lot of wheels here when changing from Metaborate to Borax, a practical experiment could be most helpful.
- Effect of PG on dev performance. Quite often I see stock developer recipes (think Pyrocat HD, PC-TEA, ...) but need only one or two rolls of film processed, so I'd like to skip the solvent for the concentrate. This would be poor advice with TEA, of course, but what about PG? PG is neither a silver solvent nor an alkali, so leaving it out should have less effect, but from what I read it does interact with the Metaborate. A quick experiment could shed some light on this.
PS: There are a few tricks which could reduce the cost of dev capacity testing: If you use fully exposed test rolls instead of step wedges, you put a lot more strain on the dev, since more silver halide gets reduced. Second, from what I read, T-grain films have less silver than traditional films, so traditional films might again need more dev than TMY2. For testing dev capacity, I'd go with the cheapest traditional 400 speed film you can find.
PPS: Since you design a dev here for very casual home developers, I'm not sure whether we need to squeeze the last penny out of its raw materials. One might as well err a bit on the high side without much financial effect.
Trying to be the best of whatever I am, even if what I am is no good.