Treating the CD-suite as PPD conversions

[laingsoft]

Can we treat, say, CD-4 in the same way as we would treat PPD? Is there an adjustment that we need to make to the formula of a black and white developer in order to adjust for the weight of the substituted group?

Also, if one were to use CD-4 as PPD, you would need to keep the hydroxylamine in order to scavenge the colored byproducts, right?

 

[Alan Johnson]

https://www.photrio.com/forum/threads/replace-ppd-by-cd-3.68079/#post-960195
PPD is a solvent and weak developer.

 

[Raghu Kuvempunagar]

Also, if one were to use CD-4 as PPD, you would need to keep the hydroxylamine in order to scavenge the colored byproducts, right?

Hydroxylamine is needed only in color developers, as a preservative, where significant amount of Sulphite can't be used. PPD-based B&W developers typically have enough Sulphite to deal with oxidation byproducts.

 

[koraks]

Can we treat, say, CD-4 in the same way as we would treat PPD?

I think you need significantly more CD4 than PPD for the same level of activity for a B&W developer. I tried a CD4-based B&W developer once; I don't think I wrote down the formula. Concentration was probably around 10g/l, using plain sodium carbonate as an activator. I may or may have not added sulfite; I can't remember. Activity was somewhat low, but a fomapan 100 negative came out perfectly well (development time was somewhere around 10 minutes or so - on the long side in any case). I didn't pursue it any further at that point because there was no compelling advantage over, say, instant mytol or so.

Also, if one were to use CD-4 as PPD, you would need to keep the hydroxylamine in order to scavenge the colored byproducts, right?

There are no color couplers in B&W film, so I don't think the 'colored byproducts' would be much of a problem to begin with. There may be some light general staining as you'd get with a poorly balanced pyro developer, but I didn't notice anything out of the ordinary with my incidental test. The negatives looked totally fine.