Relative Activity Colour Developers - one for PE?
Got a technical question regarding the following two developers - these are for developing old-style Agfacolor/Orwocolor negative films, and are copied from 'Orwo Rezepte':
A901 (Kodalk) - 3.0g
Hydroxylamine Sulphate - 1.2g
CD1 - 1.4g
Potassium Carbonate - 50.0g
Sodium Sulphite - 1.0g
Potassium Bromide - 0.90g
Sodium Hydroxide - 1.6g
Stated pH - 11.7 +/- 0.1
A901 (Kodalk) - 5.0g
Hydroxylamine Sulphate - 0.8g
CD1 - 1.7g
Sodium Sulphite - 1.2g
Tetrasodium Diphosphate - 14.0g
Trisodium Phosphate 12-hydrate - 11.0g
Potassium Bromide - 0.90g
Potassium Iodide solution (0.1%) - 5.0ml
Stated pH - 11.1 +/- 0.1
The first developer is the one indicated for developing Orwo's colour negative cine film, I have an amount of this film to play with/develop. The second developer is the standard one for the 'consumer' NC19/NC21 films.
The given time in the first developer for the cine film is 8 mins at 21*C. However, I have plenty of the second developer in kit form so I am using this to process the cine film. The trouble is, to get a reasonable density in the negative it takes around 22 minutes at 24*C -rather longer than the stated time for the 'correct' developer!
Is this because the cine film developer is more active because of its higher pH, or because its other ingredients give it different properties? Is there any way I could easily modify the developer? Could I add NaOH to raise the activity of the standard consumer developer?
If I could easily obtain raw CD1, I would simply make up the correct stuff - but I haven't had any luck sourcing any yet so need to work with what I have!
Any input from the experts here would be much appreciated.
Last edited by James1; 07-13-2013 at 03:27 PM. Click to view previous post history.
It's been a lot of years since I designed color developers, but my first guess is that the pH difference is your major problem. You can try adding NaOH, but the two developers are buffered very differently so you may have a problem raising the pH.
Thanks PP, thought that might be the case. I suspect until I do get some CD1 I will be putting up with very lengthy developing times...
I thought regular ppd was CD-1
CD-1 Chemical Name: (N,N-Diethy1-1,4-Phenylene Diamine Sulfate).
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I've got a document that lists all the half wave potentials of a massive variety of colour developers (and their mehtod of synthesis), if I can find where I put it I could share some of the data so you could at least substitution potential with other available developer agents.
Add a similar amount of sodium or potassium carbonate, then set the correct pH if needed. When fiddling around with recipes, I found a large amount of base vs a lesser amount of base helps form an image faster, even if the lesser amount is well buffered, and still more than could be neutralised by the film, even at the same pH.
Dan, half wave potentials can mislead you unless they are done at several pH values. In this case, Fred is right. The pH is probably the killer, but I would add that the Iodide has a bit of restraining action as well.
Thanks again for the input PP and PE!