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Chimie maison C-41 et RA-4

Les informations qui suivent ont été glânées sur le web, plus particulièrement un excellent post de William Laut sur rec.photo.darkroom du 27 août 1999.

Le texte dans sa version originale en anglais:

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In this post I'm documenting a couple of formulas for C-41 and RA-4 that have been requested on the ng. I've used both, and they have given me consistently good results.

Let's begin with a summary of the chemicals involved, and their current pricing from both Photographer's Formulary and Artcraft Chemicals. There are other vendors out there, and you likely will find even better pricing if you shop around. Where a price is not given, it means that company doesn't sell it. Quantites were chosen arbitrarily as a compromise between economy and price, with better savings coming in progressively larger quantities.

* Artcraft Chemicals sells its Iron EDTA in liquid form as a 47% solution.
The price listed here is derived from their 1 quart size and adjusted to reflect the equivalent of 454 grams of dry chemical.

The Sulfuric Acid is not used in any formula, but is included in the chemical list because it is an easy and effective means of cleaning the sludge that will accumulate in your storage bottles.

Formaldehyde may be difficult to obtain in your area. I've recently seen a replacement stabilizer from Unicolor consisting of Hexamine costing $10.00 for a one litre concentrate.

Tinopal SFP is an optical brightening agent that can be used in RA-4, but I'm currently trying to track down a source for it. To date I've not needed it with Fujicolor paper.

M i s c. L a b E q u i p m e n t / S u p p l i e s

You will require various sizes of graduates for measuring the liquids, a 1.5ml eyedropper (from PF) for conveniently measuring the Triethanolamine, and a scale for weighing the dry chemicals. Scales can range from the inexpensive up to pharmacy scales costing $3,000+ and precision laboratory instruments that are exceeding expensive.

At present I own two scales, an Acculab V-333 and a DRX-2 Prescription Balance. Which one I use depends on the quantity vs. precision required for the chemical being weighed.

The Acculab V-333 is a popular, modestedly-priced scale. It can measure up to 300g with a realtime digital display and has an accuracy of +/- 0.1g. I prefer to use it when its precision of 0.1g will not significantly affect the formula or when measuring quantities over 10.0g. The V-333 is available for around $140 from PF (another model, the V-200, is around $129 from Artcraft).

When either greater precision is required or when I need to prepare less than one litre of chemistry, I use a conventional "prescription balance" that I bought used from a pharmacist friend of mine. It is a Class-A torsion balance made by the Torsion Balance Co. of Clifton, N.J., and is their model DRX-2.
It has a capacity of 120 grams, and an accuracy of +/- 0.001g with legends marked in 0.005g increments. Back in 1995 these units sold brand-new for around $1,100 without weights, although you can buy them used in good condition for $200 to $500. A weight set for this type of balance can run from $20 to $150.

You will also need to purchase "powder papers." These are made of vegetable parchment and range from 2"x3" to 4.5"x6.5". They are sold in boxes of 1,000 sheets for $12 to $20. They are used to protect the balance's weighing pan and to eliminate contamination from trace amounts of the previous chemical weighed on the scale. They are used once and then discarded.

You may also wish to order some stainless-steel "balance spoons." These are used for conveniently removing the chemicals from their bottles and placing them on the scales, especially for precision measurement when you must tap the chemicals onto the weighing pan a few grains at a time.

You should also purchase a small mortar & pestle for grinding some chemicals (such as some brands of Potassium Bromide) into small sizes for precision weighing.

The powder papers, balance spoons and mortar & pestle can be ordered through your local chemical supply house or friendly pharmacy. You can also order them from Apothecary Products, Inc. Their phone number is (800) 328-2742.

I recommend that you store the CD-3 and CD-4 in tightly-sealed brown -glass-jars, to maximize their storage lifespan.

Finally, you should store the acids and alkali in separate cabinets.
DO NOT  STORE ACIDS AND HYDROXIDES NEXT TO EACH OTHER IN AN ENCLOSED CABINET!!

RA-4 Color Print Formula

The developer for this formula was first published by Dr. Robert Chapman in PT, and was supplied to me by Ron Speirs and Bill Cox (thank you both). I have slightly modified it to include the optical brightening agent, Tinopal SFP, and optionally Potassium Hydroxide for using it at room temperature.

Please note that because of the necessarily limited amount of Sulfite, the RA-4 developer does not have a long shelf life. I have used it up to 48 hours after mixed, but I wouldn't go much longer than that.

While this developer is intended for use at 95F, it can be used at room temperature if you either extend the development time to around three minutes, or add around 5.0g of Potassium Hydroxide. For those wanting an "AT" kit, you will have to experiment to find a time suitable for yourself.

Since my preference is for one-shot processing, I'm still experimenting with this developer to see how dilute I can make it and still obtain good results, with the objective of making it as inexpensive to use as possible.

The Blix I reverse-engineered from a Beseler RA-4AT kit, and then diluted it down for economical one-shot processing, requiring 60ml per 8x10. If you wish to use this Blix formula for tray processing, you will likely have to concentrate it. Also, please note that the original Beseler kit included Ammonia in its Blix to counteract the cyan leukocyte staining that could result from stop bath carryover acidifying the Blix. Rather than complicate the formula by adding unnecessary chemicals, I have instead omitted the Ammonia in favor of adding a rinse between the stop and the blix.

* Only add the Hydroxide if you are planning to use this developer at room temperature with no additional development time. You may also see a color shift towards cyan which you will have to correct for in your filterpack.

** The use of Tinopal SFP is optional in this developer. I recommend you try using the developer first without the brightener to see if you actually need it with the paper of your choosing.

* If you are using Artcraft's 47% Iron EDTA, use 22.0ml for this step.

Preparation Notes

I recommend using the 1.5ml dropper from Photographer's Formulary for measuring the Triethanolamine, because it is a -very- thick, syrupy liquid.
When measuring out the TEA, you will make four 1.5ml measurements. Between measurements allow the TEA to accumulate in the dropper and then "squirt" it into the graduate so that all of the measured liquid is correctly put into solution. After the four measurements are taken, rinse the dropper out (both inside and outside) in the graduate so that all of the TEA is put into the solution.

N.B.: TEA is a strong alkali that can cause chemical burns on your skin! 
Handle it with due care to avoid getting it on your skin.

In the RA-4 developer the Sodium Sulfite acts to inhibit excessive dye formation and the Sodium Chloride is the restrainer. Since small quantities are involved, you may have trouble attaining consistency from one batch of developer to another if you use an Acculab scale to directly measure these, since its accuracy is only +/- 0.1g and that can (in this case) introduce a variance of 10% or more. If you don't have access to a torsion balance to weigh the sulfite and chloride and you are experiencing batch-to-batch changes in the developer's performance, you may instead wish to prepare percentage solutions as follows: 

Sulfite Solution

Chloride Solution

Substitute 50.0ml of the Sulfite solution and 25.0ml of the Chloride solution for their dry chemical counterparts in the developer formula.

The Blix will not be as opaque as you normally see from commercial kits. This is due to its having been diluted down for one-shot processing.

* The development time may need to be adjusted on a per-paper basis to obtain an ideal D-max. For example, one minute is sufficient for Fuji Super FA5 "G" surface, while 1:10 is better for Fuji Super FA5 "L" surface.

C-41 Color Film Formula

Here's the C-41 Formula. It was published by Zone V (not to be confused with Fred Picker's Zone VI), and supplied to me by Ron Speirs (thanks, Ron).

IMO, it is somewhat "hotter" than commercially packaged C-41 developers, and as such may be an ideal candidate for pushing color neg film, especially at temperatures greater than 100F (although any variance from 100F is -not-recommended and should be experimentally proven out before applying to important work).

Sulfite in CD-3 developers is used to prevent excessive dye formation, and I've seen the same phenomena occur with CD-4, so it may be possible to use this developer to push color neg film and at the same time slighly increase the Sulfite content to prevent the highlights from getting blocked up (which this developer will quite easily do). In this regard, adding additional Sulfite could be likened to the effect of using an extreme compensating Catechol developer on B&W film - you get fully developed shadows without blocked-up highlights. This is still theoretical, and sometime I hope to have the time to sweat the details out with a 100-foot roll of film, a Macbeth Colorbrator, and my transmission densitometer.

Films that are shot in bright sunshine may have to get pulled slightly to keep their highlights from blocking up. This is something you will have to experiment with, in order to find the ideal exposure index and development time for shooting your film under bright sunshine.

When used to develop film that has been nominally over-exposed by 1/3-stop from the manufacturer's rated speed, the colors are vibrantly saturated with full contrast.

I've not gotten around yet to experimentally diluting this formula, to see how far I can stretch the chemicals and still get excellent results with one-shot processing. I will be doing that sometime later this fall and will report the results back to the ng at that time.

* If you are using Artcraft's 47% Iron EDTA, use 54.0ml for this step.

* For the "Dry Warmup," put the tank containing the film into a tempering bath, and allow it to warm up for five minutes before commencing with the development. Please note that you do NOT put tempering water into the tank, as this will induce color shifts.

Preparation Notes

NOTA BENE: Hydroxylamine Sulfate is a corrosive, hazardous substance! It will cause chemicals burns and can stain when alkaline. Be careful not to get any on your skin. Read the MSDS carefully for handling instructions.

Alternate Bleach & Fixer

If you wish, you can also use a separate, more economical Ferricyanide Bleach and Fixer. They cannot be used together as a Blix, since Ferricyanide and Thiosulfate are unstable together and neutralize one another.

If you wish to compound your own fixer from bulk, Dr. Robert Chapman published the following formula:

The Bleach and Fixer can be reused until the the bleach/fixer times extends beyond the times listed above.

Bottle Cleaning

In my experience, both C-41 and RA-4 have a tendency to build up a sludge along the sides of the storage bottles. I've found the easiest way to clean out this sludge is to put 750ml of hot water into the storage bottle, and then add about 10-15ml of 48% Sulfuric Acid to the water. Tightly screw on the cap and then gently shake the bottle. The acid will quickly dissolve the sludge.
Dump the water and then thoroughly rinse out the bottle before adding fresh solution to it.

N.B.: The Acid will generate heat as it mixes with the water, so don't use excessively hot water to begin with.

Cost Analysis

Finally, I'm including a gross cost analysis of preparing C-41 and RA-4 from bulk chemicals. Easily, the most expensive chemicals in either process are the dveloping agents (CD-3 and CD-4) and the Ferric Ammonium EDTA.

The difference in price for the Bleach (Iron EDTA) between Artcraft and PF amounts to about two cents per gram, and for the CD-4 it's about 2.5 cents per gram. At five grams per litre, the cost difference is only $0.13 per litre on who's CD-4 you use. However, for the Bleach the difference is significant enough IMO that I've provided a side-by-side comparison for you to decide whether you want to measure it on a scale or in graduate. :-)

Not including the cost of the scale(s) or other sundry lab equipment, the chemical-only cost per litre is:

At 61ml per 8x10, this will process 16 8x10s for $0.15/$0.13 (PF vs. AC's Iron EDTA) per 8x10.

Using the Jobo 256x six-reel tank (850ml), the cost per 35mm roll is $0.6531/$0.5837. If you use the Jobo 252x tank and process two rolls at the same time, using 250ml of chemistry (and diluted to 270ml to correctly fill the tank), then one litre will develop eight rolls of 35mm film at a cost of $0.5763/$0.5150 per roll.

For medium-format users, the cost (using a Jobo 252x tank) is $0.70 per roll of 120, and $1.10 per roll of 220.

Large-format (4x5) using 2509N reels varies in cost, from $0.185 per sheet (six sheets in a 252x tank) to $0.229 per sheet (18 sheets in a 2583 tank).
This variance is due to chemistry volume differences in the 252x vs. 2538.

As for the RA-4 cost of $0.15 per 8x10, well, you can compare _that_ for yourself to what your local pro lab would charge you for printing an 8x10.

The cost savings of mixing from bulk versus mixing from a commercial kit diminishes as you buy larger kits, but does not disappear altogether until you buy a 125-litre kit.

Obviously, I cannot place a dollar amount on the value of your own time, so I cannot factor that into the cost analysis and thus that'll have to be your own call. In preparing these formulas, without pushing myself I find that it takes about 45 minutes to prepare the RA-4 and about an hour to prepare the C-41. These times include all prep work and post-mixing cleanup.

Closing Thoughts

For myself, the principal advantages of mixing color chemistry from bulk chemicals are as follows:

1) Batch-to-batch consistency. When I first started in RA-4, I was dismayed to see how often my filterpacks would vary from one kit to the next. It was simply unpredictable, and in retrospect I believe I was seeing the same thing that Curt Miller saw in dealing with prepackaged PMK - the alkali was being neutralized by CO2 that was permeating the plastic bottle.

By contrast, in the last two weeks I've probably gone through about ten litres of RA-4 using the enclosed formula, and there has been _no_ variance whatsoever. No wasted test prints, no readjustments to the trial filterpack, nothing but predictable, satisfying, 8x10 and 16x20 color printing.

2) Long shelf life. The chemicals, in their dry form, will last nearly indefinitely on the shelf. For example, my supply of CD-4 is about 1.5 years old, and this week I used some to make 250ml of C-41 to process a couple rolls of Fuji Reala with excellent, predictable results.
Compare that sort of lifespan to a partially-used RA-4 or C-41 liquid concentrate.

IMO, if you don't do color work regularly, then this benefit alone could justify the added work of mixing the chemistry from bulk chemicals.

3) Easy ratioing. Since the formulas are metric, it's easy to divide them to make as much or as little as is needed without any waste.

4) Low cost. The greatly reduced expense makes color film developing and printing _fun_ again, without the angst of seeing another buck or two of chemistry wasted on yet another blown print. This is especially merciful to those who are new to color printing, as it allows them to learn how to successfully print without the grief of going through possibly hundreds of dollars' worth of kits, or of trying to squeeze the life out of every last drop of developer, and possibly introducing color shifts in the process.

On the negative side, the only disadvantages I could identify is the inconvenience of having to learn how to weigh dry chemicals on a scale, and the initial high investment cost (around US$400). However, in that initial investment you not only buy all the required lab gear, but also enough chemicals to make twenty litres of RA-4 -and- twenty litres of C-41.

You could spend the same amount of money buying twenty one-litre kits of RA-4, and have nothing left over to process your negatives, so the high initial investment is not as bad as it first seems.

Anyway, those are the formulas. Enjoy them, and as I come up with refinements I'll post them to the ng. If anyone comes up with improvements, please post them as well.

Regards,

Bill Laut

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