Color developer formulas collected: C41, ECN2, RA4

koraks · Oct 13, 2022

While I mostly use industrially produced color chemistry, I have messed with compounding my own color developers in the past - and there's a good chance I will at some point continue doing so if the situation calls for it. In the process, I searched a lot for good and practical (which is not always the same!) information on color developer formulas. While most/all of this can still be found if you google a bit, and most of the relevant stuff is even right here on Photrio, I still spent quite some time over the years compiling, comparing and combining information from various sources. Basically, what's out there is pretty good most of the time, but it's also fragmented.

For this reason, I made a start today putting it all together and selecting what I believe are the most essential sources of color developer formulas and summarizing this essential information in one place. You can find the fruit of this labor through this link:

Color me purple – Some color developer formulas including C41 and RA4 – Koraks tinkers

tinker.koraks.nl

Again, I emphasize that the information on that blog isn't new, it's not something I made up or developed, and all credits go to the respective sources, which are explicitly linked to on my blog. All I did was assemble it in a way I thought might be useful for others who face the same challenge I once did.

Comments, corrections and additions are welcome; I'll try to work them into the blog post (if relevant, of course).

Mick Fagan · Oct 13, 2022

Very nicely done, thanks.

Steven Lee · Oct 13, 2022

@koraks this is awesome, thank you.

koraks · Oct 14, 2022

Thanks gents, I hope it'll serve you well!

Javier Salvalle · Oct 14, 2022

Thanks Korak,

Very cool information.

koraks · Oct 14, 2022

Thanks Javier!

Sonynolta User · Oct 14, 2022

Nice compilation of knowledge. This info is often 'out there'- but where? And need sortings through to make sense of it all. This is a nice service to those that want to know- and learn- more.

brbo · Oct 14, 2022

Excellent!

(I hope I'll never need this information)

koraks · Oct 14, 2022

Sonynolta User said:
This info is often 'out there'- but where?

That was exactly the challenge I met when I wanted to roll my own!

@brbo thanks! And I also hope we'll be able to enjoy the luxury of good industrial developers for a long time to come. Of course, when those become unavailable, the odds are that the source of CD3 and CD4 also dry up at about the same time, so we'd still be stuck (apart from remaining stocks).

MattKing · Oct 14, 2022

So now we have two threads from koraks in this sub-forum that have been made "Sticky" threads .

koraks · Oct 14, 2022

My pleasure, @MattKing

Janosch Simon · Oct 16, 2022

your the man thx koraks

koraks · Oct 16, 2022

Thanks Janosch, always a pleasure May this collection may give you fun in your many interesting darkroom experiments!

lamerko · Jul 21, 2023

Hello,
Can the C-41 concentrate formula be changed to a 1:5 / Stock A:Stock B ratio? For example as follows:

Stock A (for 5 liter)
Hydroxylamine sulfate (HAS) - 12.05 g (58.7 g/100 ml (20° C))
Water up to - 100 ml

Stock B (for 5 liter)
Potassium carbonate (anh) - 171.5 g (110.3 g/100 mL (20° C))
Potassium bicarbonate - 11.6 g (22.4 g/100 mL (20° C))
Sodium metabisulfite - 13.9 g (65.3 g/100 mL (20° C))
Sodium sulfite (anh) - 1.9 g (27.0 g/100 mL (20° C))
Sodium bromide - 6.55 g (94.32 g/100 mL (25° C))
Potassium iodide (*) - 6 mg(!)
Water up to - 500 ml

Dilution for 1 liter
Water - 880 ml
Stock A - 20 ml
Stock B - 100 ml
CD-4 - 4.52 g

The solubility of potassium carbonate in water is 110.3 g/100 mL, which is good, but will the rest of the ingredients be able to dissolve if we have already mixed 340 g of carbonate (*per liter)?
The aim is not to keep too much concentrate for a long time, and also that the proportions for both parts arrive at an equal amount of working solution.

koraks · Jul 21, 2023

You'll have to try, but I don't foresee any particular problems.

Does your math pan out, though? E.g. for stock B you're using 100ml to 1 liter of developer, whereas my formula uses 140ml for the same liter. But your stock B is less concentrated than mine (and also of a quite different formulation altogether). Looking at the C41 formulae and the carbonate specifically, it's usually around 30-35g/liter in working dilution, but you seem to be aiming at about half that amount. Something doesn't add up - or did you mean to use 200ml stock B for 1 liter of working strength?

lamerko · Jul 21, 2023

Yes, as math comes out. The chemicals are slightly different because I have based on the PE's formula. There they require 34.3 g of potassium carbonate (anhydrous, but I have one) for 1 liter of working solution. I calculated 171.5 g in the concentrate, but notice that concentrate B is 500 ml, not 1 liter. This actually makes it more concentrated than your formula. For concentrate A, I have reduced the concentration by half. So the two parts would make a total of 5 liters of working solution.
My idea is not to have a large amount of concentrate because I don't use C-41 films that often. When processing, I dissolve 500 ml of working solution, which is enough for two films. And maybe four, if there are quick throws. Тhis formula would give me 10 x 500ml working solution - perfect for me. The entire amount will be enough for 20 to 40 films - even that would be more than I need. For storage, I use 500 ml PET bottles - they are very convenient, because they close tightly, do not let oxygen in and can be closed tightly, without an air chamber. I also have smaller glass jars - perfect for storing 100ml of concentrate.

-= EDIT =-

Now I see where the confusion is. I've been doing several calculations and I've copied from the wrong last part...

Dilution for 1 liter
Water - 880 ml
Stock A - 20 ml
Stock B - 100 ml
CD-4 - 4.52 g

It should be read like that

Dilution for 500 ml
Water - 880 ml
Stock A - 20 ml
Stock B - 100 ml
CD-4 - 2.26 g

koraks · Jul 21, 2023

lamerko said:
notice that concentrate B is 500 ml, not 1 liter.

Gotcha! That's it.

Your oxygen-sealing strategies will come in handy to protect that tiny amount of sulfite which apparently is there to prevent excess dye formation. I guess the developer won't work as intended if it degrades.

Formulahunter · Aug 24, 2023

I made a table for the concentrates mentioned on Koraks blog for Photo engineers Formula

Concetrate A:	Developer	Concentrate
HAS	2,41 g/L	241,00 g/L
make to 1L
Concentrate B:
Potassium carbonate anhydrous	34,30 g/L	245,00 g/L
Sodium Bicarbonate	1,95 g/L	13,93 g/L	ORIGINALLY Potassium bicarbonate	2,32 g/L	16,57 g/L
Sodium Metabisulfite	2,78 g/L	19,86 g/L
Sodium Sulfite	0,38 g/L	2,71 g/L
Potasium Bromide	1,52 g/L	10,86 g/L	ORIGINALLY Sodium Bromide	1,31 g/L	9,36 g/L
Potassium Iodide	1,20 mg/l	8,57 mg/L
DTPA 40%	8,43 ml/L	59,57 ml/L
make to 1L
Part C:
CD-4	4,52 g
To make XX of developer	1,00 L	0,60 L
Part A	10,00 mL	6,00 mL
Part B	140,00 mL	84,00 mL
Part C	4,52 g	2,71 g
Target PH of developer:	10,0 +/- 0,05 @25°C

koraks · Aug 24, 2023

Cool
Have you tried it, already? Please let me know how it works for you!

Formulahunter · Aug 24, 2023

koraks said:
Cool
Have you tried it, already? Please let me know how it works for you!

For the concentrates I just did the math for now.
But the I use the recipe with SBC for PBC and PB for SB for quite a time by now and had great results with it. (They are just more readily available to me)
Its well known that you can use Potassium and sodium salt pretty much interchangeably if you take the molecular weight into account.

koraks · Aug 24, 2023

Yes, I don't doubt the sodium/potassium substitution works perfectly fine here!

drp · Oct 14, 2023

donttouchthenegative:
How did you get the sodium sulfite amount of 0.78g/L when Photo Engineer's formula has it at 0.38g/L? I'm curious to know how you did the math? It looks like there is a multiplier of about 7.14. Is that accurate? Would it change the sodium sulfite to 2.7g/L for the concentrate?

To either donttouchthenegative or koraks:
How long does the concentrate last?

I'm about to embark on both the C-41 and ECN-2 formulas as well.
Thanks!

Rudeofus · Nov 1, 2023

drp said:
donttouchthenegative:
How did you get the sodium sulfite amount of 0.78g/L when Photo Engineer's formula has it at 0.38g/L?

There appears to be more than one error in this table: 8.43ml DTPA-Na5 40% solution turned into 8.34 ml DTPA 40% solution, insolubility of DTPA free acid notwithstanding ...

Formulahunter · Nov 2, 2023

Rudeofus said:
There appears to be more than one error in this table: 8.43ml DTPA-Na5 40% solution turned into 8.34 ml DTPA 40% solution, insolubility of DTPA free acid notwithstanding ...

unfortunatley i cannot edit the post anymore.
With the low solubility of the freebase, you'll find many souces only write 40%DTPA meaning the 5Na salt of course.

koraks · Nov 2, 2023

donttouchthenegative said:
unfortunatley i cannot edit the post anymore.

Should now be fixed in post #18. I've removed some follow-up messages that were part of the process of patching things up.

In cases like these, please use the 'report' function and we'll happily edit out any of these typos!

Color developer formulas collected: C41, ECN2, RA4

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