PE: after a couple of days of C-41 processing (ready kit) a couple of thoughts as not to drift OT too much. First of all thanks for the hints regarding Iodide salts which I will happily take into consideration. By now I even translate the use of Iodine to the more accurate Potassium Iodide. Your question whether finding a fault in a formula wouldn't put me off it. Yes and no.

Let me explain. You refer to 'the' C-41 formula. While I am happy to believe that there might be such a thing (or not), it certainly is not available to myself. The few patents I looked at also don't give this information away. Why should they? As you explain yourself, the real life C-41's (plural) have probably mutated a fair amount. This can be due to product development as you state or difference between companies, environmental protection rules, etc. After just purchasing a bottle of Kodak Stabilizer & Replenisher III with formaldehyde, I read its replaced by a formaldehyde free one. I'm sure the store (Silverprint, London) is happy to be rid of the old stuff.

Having just used the Fotospeed PK-C41 kit I have also found out how unstandard things can be. I will detail my results in a thread yet to come but the short of it is a dilution of 1+3 rather than 1+2 and a reduction in dev time by 20% gave near correct results. Option 1 (negative): Fotospeed does not know how to mix C-41. Option 2 (more positive): there is a clear reasoning for their formulation behind this but not visible to me and the world. A possible conclusion could be to a) stick only with brand name kits. b) from now on only use Fotospeed as I have now figured out how it works.

Now looping back to my reasoning why self mixing and clarification of the formulae is something I like. In a word: control. Not a single manufacturer will tell me, brand or non-brand, what's in the package. I am waiting for the day when chemistry dealers apply the (software) open source concept and start offering premixed kits _and_ declare precisely what's in them. has such kits, but I have not seen content declarations. Besides, they still have not replied to email and not answered the phone either. So yes, published homebrew formulas may be deviant from a possibly obsolete formula tucked away in some safe. And they may need modification to improve performance, but they may be just as deviant as real life preparations. The difference is that the formula is something I can modify, but not so with prepacked stuff. If something goes wrong, I am completely in the dark. I simply cannot tell how much, if any, Potassium Iodide is in Brand X developer. I don't even know if they are still using CD-4 or one of its hundreds of variants as Kodak proclaims in a patent.

The advantage I see with using eg Kodak over Photospeed is not my belief that the chemistry is inherently better, I don't know that and I do not trust sales speak, but rather that their documentation is much better. This gives me detailed info which I appreciate.

So, yes, it worries me to find a fault, but no, not to much. I find enough faults in pre-packaged stuff as well. Self built computers and Big Brand ones both have problems as well. I have always self built.

That is the reason why input by people like yourself who do have more insight into the chemistry are valuable in this forum. Giving info like you did about the Potassium Iodide together with an appropriate reasoning gives understanding. With that I can then decide whether to modify my approach or not. I just prefer informed decisions rather than trusting 'we are so good and the best' talk.

In that sense, if you could look at this formula (source early in this thread) and a) make suggestions as what to add, remove or modify b) and, this is in line with my original intent of this thread, because Hydroxylamine Sulfate is considered too unhealthy and therefore difficult to get, how that can be substituted. I guess a first addition would be 1.0g Potassium Iodide.

Thanks for any help!

Water (Room Temp) 800.0ml
Potassium Carbonate 32.0g
Sodium Sulfite 3.5g
Potassium Bromide 1.5g
Hydroxylamine Sulfate 2.0g
CD-4 5.0g
Water to make 1.0L