[2017-10-29: This article was originally posted here on the Photrio web-site. A bottle of this concentrate (and the similar D316 developer) have been in my freezer for about 4.5 years, and they are still fully active with no yellowing, so Mocon will last over 4.5 years when kept frozen. The original article is below.]Mocon is a two-part developer consisting of a long-lasting liquid concentrate and sodium sulfite powder used one-shot. It was originally intended to be an XTOL-clone, but it turned out to be not quite that. Mocon generally gives slightly finer grain than XTOL and slightly lower true film-speed. To match XTOL, you can modify Mocon, or try Mocon-X which is also described in this article. Mocon stands for “Mark Overton’s Concentrate”, and its temporary name was 214D. The goal of this project was to create a concentrate that lasts a long time (over a year), and that gives the image-quality of XTOL. This developer is intended for those of us who don’t shoot enough B&W to consume 5 litres of XTOL before it goes off.
Method 1: Alan Johnson had the following idea which makes using this concentrate as easy as Rodinal. First, make a batch of sulfite solution by mixing 46 g/L sodium sulfite into distilled or DI water. Make enough to last a couple of months given how much shooting you do. You can refrigerate it to ensure longevity. To make working developer:
Method 2: If you don’t want to keep sulfite solution around, you can mix working developer as follows:
The pH is 8.08. An electronic scale with .1 or .01 g resolution only costs US$12-15. That’s the cost of three rolls of film, so there’s no excuse to not have one (or two). Search for “scale .1 g” or “scale .01 g” on amazon.com.
Quiz: Why does sulfite solution contain 46 g/L of sulfite instead of 45 g/L as used in method 2?
When stored frozen (preferred) or refrigerated, it should last over a year and probably over two years frozen. At room-temperature, count on six months. If you store it frozen, and forget to take it out of the freezer ahead of dev-time, you can immerse the bottle in a pan of water, which will quickly warm it to room-temperature. I don’t advise opening the bottle when frozen to avoid condensation adding water to the concentrate.
Propylene glycol 12.2 g (same as 11.8 ml) Sodium metaborate 4 mol 1.8 g Ascorbic acid 4.2 g Dimezone S 0.08 g (or .05 g Phenidone, but note issues below)
As mentioned above, Mocon generally gives slightly finer grain and slightly lower film-speed than XTOL. However, this difference varies among films. For example, I could see no difference with Tri-X. The speed-loss is small enough that I’ll accept the finer grain in trade. If you want the same film-speed as XTOL, boost Dimezone S to .1 g/L in the concentrate and reduce dev-time by about 5%. For pushing, I suggest boosting Dimezone S above .1 g/L, but this change needs testing.
Tri-X 13.5 T-Max 100 14 (see note below about early shoulder) T-Max 400 13.5 Delta 100 12.25 Delta 400 18 (see note below about long toe with Phenidone) Delta 3200 25 or longer (not recommended due to some speed-loss and long dev-time) Pan-F+ 12.25 FP4+ 16 HP5+ 15 Acros 15 Neopan 400 14.25
If you choose to use Phenidone instead of Dimezone S, you’ll see two changes. First, Delta 400 will get a longer toe, so you should rate it at 200 or slower. Second, Phenidone increases fog by .02-.10 depending on film. Neopan 400, FP4+, Delta 100 and Delta 400 get the greatest fog-boost. T-Max 400, Tri-X and HP5+ get little fog-boost. I recommend Dimezone S which can be purchased in both Europe and the USA with international shipping. Mocon has the following advantages over XTOL:
Mocon-X, which had the temporary names of 119D and 119P, produced results identical to XTOL with the few films tested. Its one-litre formula is:
G=10g, M=1.5g, A=3.5g, D=.1g -or- P=.05gHere are the few times that I determined:
Usage: 14.7g concentrate and 45g sulfite in 1L of dev (pH=8.15)
Notice that these times are slightly lower than those for D316 described below, so the D316 times minus a bit would be good starting points.
Tri-X 13 HP5+ 14.25 Delta 400 17.5 Neopan 400 16.25
If you want to create a developer that’s good for pushing, I suggest boosting the Dimezone S in Mocon-X to .12g or higher. I think the increased concentration of developer will cause increased exhaustion in midtones and highlights, giving the toe more time to develop, increasing true film-speed. But grain will be a little worse.
D316 was first formulated in January 2012, was tested thoroughly, and performs similarly to Mocon, but I rejected it because it produces a longer toe with Delta 400, and also because it can only use Phenidone (not Dimezone S), resulting in higher fog. Its one-litre formula is:
G=16ml(=16.6g), M=2.2g, A=4.5g, P=.05gThe times for D316 are:
Usage: 20ml (=22.8g) concentrate and 45g sulfite in 1L of dev (pH=8.08)
Locon-1 was another discovery from January 2012, and is suitable for pushing or low contrast. But it has had little testing. Its formula:
Tri-X 14 T-Max 100 13.75 (shoulder is higher than Mocon, but still lower than most films) T-Max 400 12 Delta 100 13 Delta 400 17 Delta 3200 25 or longer Pan-F+ 12.25 FP4+ 16 HP5+ 14 Acros 13.5 Neopan 400 16.5
G=17.5ml, M=1.2g, A=2.8g, P=.15gTo reduce fog, I suggest using .2 or .25 g of Dimezone S instead of Phenidone. Starting dev-time is 8-10 minutes for T-Max 400. This formula has relatively little ascorbic acid and sulfite, so restoration-rate will be lower and thus the developer will exhaust more quickly in midtones and highlights, so the toe will develop even more than modified Mocon-X.
Usage: 20ml concentrate and 35g sulfite in 1L of dev (pH about 8.2)
The SMAP of (90, 6.7, 8.5, .2d) is a developer with the same dev-times as XTOL, same image-quality and same pH. It appears to be a clone of XTOL in all respects. But the concentrate crystallizes after a week or two, separating into a cream and liquid (more about this problem below), so it’s unusable as a concentrate. However, you can mix the formula directly into water and omit the propylene glycol. If you want to try this, I suggest dissolving the Dimezone S in a separate 2% solution of propylene glycol to make the small quantities easy to measure. Also, propylene glycol changes developer behavior a little, and its absence means you might need to change the 6.7g of metaborate a little to perfectly match XTOL. Rolls of HP5+, Acros and Tri-X all matched XTOL.
PC-Sulfite is what I call the “D-23 of PC developers” because it’s so simple. Its SMAP is (90, 0, 2.8-3.5, .15p). Notice that it has no sodium metaborate. Add about 15% to XTOL’s times. Grain is the same as XTOL or a bit worse, depending on film. Although I haven’t tested it, I suggest using .2g of Dimezone S instead of Phenidone. Using less Phenidone or Dimezone S should improve grain a little. Peter Svensson independently discovered it 5-1/2 years before I did, and his SMAP was (64, 0, 3, .08p). Here’s my posting about it: http://www.apug.org/forums/forum37/99921-pc-sulfite-simple-developer-giving-xtol-quality.html Here is Peter’s posting: http://www.apug.org/forums/viewpost.php?p=313770
Here are some more interesting SMAP developers that I haven’t had time to pursue. Each has been tested only once, except Instant Mytol which I’ve never tried. All except Instant Mytol can be mixed as a concentrate:
(75, 1.5, 4.5, .08d/.05p) My notes say “top quality”. Use about 2X XTOL’s times.
(90, 4, 10.7, .15p) Grain a bit better than XTOL. Add 30% to XTOL’s times.
(90, 4.1, 9, .2d) Matched XTOL; a promising clone.
(60, 7, 11.5, .15p) This is Instant Mytol, by Jordan Wosnick.
“PC” developers are those which use Phenidone or Dimezone S in combination with ascorbic acid or sodium ascorbate. The major problem with PC developers when mixed into water is the catalytic Fenton reaction, in which iron and copper impurities slowly destroy all the ascorbate. This is true even if using distilled or DI water, because the iron and copper come from your own chemicals. With a high quantity, it’s been reported that substantial ascorbate-loss can occur within one hour. XTOL uses DTPA-Na5 as a sequestering agent to remove these metals, and you can too if you can find some DTPA-Na5. Or you can create a concentrate using propylene glycol or TEA. No water means no Fenton reaction. But the ascorbic acid in these concentrates slowly oxidizes, causing them to turn shades of yellow and then shades of orange. At room temperature, they seem to last about 6 months without excessive ascorbate-loss. However, I have found that glycol-based concentrates can be stored chilled or frozen with no precipitation, so I strongly recommend doing so. I suspect they’ll last years in the freezer.
All the concentrates described in this article take advantage of these discoveries that I’ve made:
If you are designing your own developer, be sure to test T-Max 100 (TMX) and Delta 400. TMX has an unusually early shoulder with many developers, and you’ll want to know where your dev puts it. Delta 400 can easily get a soft toe, so keep an eye on that one as well, comparing the toe with that from a common developer such as D-76 or XTOL. I suggest testing all B&W films made by the big-three makers (Ilford, Kodak, Fuji). These are only 11 films, and it only takes a few weeks to test all of them.
A factoid that’s nice to know: When dissolving the MAP chemicals into propylene glycol, the volume of the liquid in ml will increase by about 0.6 times of weight of those powders in grams. This lets you predict the volume of the resulting concentrate.
And my final bit of advice to designers of developers: Get a densitometer and a Stouffer step-wedge. It’s the only way to know what your dev is doing around the toe, where and how quickly it shoulders off, and if there are any anomalies in between.
Whew! Now that this project is over, I’ll have some spare time to do some shooting.
Mark Overton, 2013-4-6