D-23--Would it benefit from a chemical buffer?

[lensmagic]

Film developer D-23 has but two ingredients, metol and sodium sulfite. Would buffering the system produce better results? I am confused as to whether the buffering agent should be sodium metabisulfite, sodium metaborate or sodium bisulfite.

 

[Christopher Walrath]

It is sodium bisulfite in D25 (identical recipes, just add 15g sodium bisulfite per litre of developer). It can be replaced with potassium metabisulfite by increasing volume an additional 6% over the recommended amount of sodium sulfite or with sodium bisulfite by reducing its volume to 91% that of the sodium sulfite.

 

[Gerald C Koch]

D-23 has a buffer, it is the sodium sulfite. This chemical has several uses in photography. If you add another buffering agent then it's not D-23 any more.

D-25 works by lowering the development rate below that of D-23. Therefore the film must remain in the developer longer causing greater solvent action.

 

[CBG]

There's no intrinsic need to buffer. D-23 is complete unto itself.

 

[BradS]

I agree with Gerald and CBG. There is no need need to buffer D-23.

Further, Sodium Bisulfite and Sodium metabisulfite (they're same thing) are not really buffers. They would lower the pH of D-23 and make something completely different (D-25) as Christophe noted.

Sodium Metaborate would be a good buffer but, it too is not necessary and would alter the activity of D-23.

Best to leave a good thing alone.