accelerator used in B&W developers: quantify energy level please

Sodium carbonate, monohydrate (hereafter, SCM) is probably the most widely used accelerator for B&W developers. But, you also have others such as borax and Kodalk. Sometimes we need to use a very powerful accelerator like sodium hydroxide.

Can anyone quantify the energy level for each, using SCM as a benchmark. In other words, one gram of SCM equals (how many) grams of borax? Of Kodalk? And, many of us already know that sodium carbonate, anhydrous (heated baking soda) is even more powerful, gram per gram, than SCM is.

Finally, is substitution without other effects? Are there advantages/disadvantages with using one over the other? Stability? Consistency? Other factors?

- David Lyga

And, Michael, (thank you for your profound explanation), it is, indeed, not as simple as I wanted it to be. And that is why, even with my desperately poor chemistry understanding, I continue to use sodium bicarbonate, which seems to 'buffer' my mixtures.

Your quote is rather interesting: "(for example substituting a lower amount by weight of carbonate anhydrous for carbonate monohydrate) it may not always be thay (SIC) simple. There are formulas in which a crystaline form is called for specifically because there will be some carbonate-bicarbonate buffering."

I do not know why or how, but my adding a bit of baking soda seems to balance things out. I cannot quantify why I do this but my experience seems to indicate that the developer is more reliable and 'smoother' for acquiring density. I have to admit again that this warning of even differences between sodium carbonate MONO and ANHYDROUS is rather amazing to see; differences that transcend mere quantity and potency. Thank you. - David Lyga

Yes, and I agitate continuously, in a water bath, at all times for both B&W and color. That is my standard method and I have no complaints.

So then, Michael, it is not only a matter of the developer exhausting itself locally where there is increased density. The PH there is lowered as well and THAT adds to the slowing down. But that 'slowing down' is mitigated, indeed, prevented, by my constant agitation. - David Lyga

If you were to start again and say the pH is all you need to worry about that would also be a simplification.

eg POTA has a pH around 8.5 to 9.5 from sodium sulphite but the sulphite also activates the phenodine by clearing its reaction by product supposedly so nothing is simple.

If your mix for spell 37 works don't lose the recipe.

Generally, substituting one alkali for another changes the pH, and therefore changes the characteristics of the developer, including developing time and contrast. Even if you keep the pH the same, by careful buffering, the activity may change, and the look of the result will be different.