The hydroxides have been widely used with pyrocatechin based developers and it should come as no surprise that they give greater activity with pyrocatechin than the carbonates. In the Pyrocat-HD formula, to get to the same pH, and energy, you must substitute carbonate for hydroxide at about a 10:1 ratio. You could also substitute tribasic sodium phosphate at about the same ratio, or slightly less. However, there is a lot more to a good developer than its level of activity or energy.Originally Posted by jdef
When I developed the Pyrocat-HD formula I experimented with numerous activators, including the hydroxides, the carbonates, and TSP. Based on several criteria I concluded that the carbonates, in spite of the fact that they are not as efficient as the hydroxides, are a better and more rational choice for this developer. With carbonate the stock solutions are more stable, the working solutions are better buffered, and there is less chance of pin holes on the negatives, especially when using acid stop baths. Also, the grain is definitely finer in the Pyrocat-HD formula with carbonate.
So, while there is no doubt in my mind but that the hydroxides work very well with pyrocatechin based formulas such as Pyrocat-HD, and they are definitely more efficient in some respects, I simply don't think they are the best choice.