Still the best and easiest to mix is the phenidone-ascorbate in water. Phenidone is less sensitive to bromide content than just about anything other than (perhaps) amidol. That means that it will make a long lived developer in a self replenishing system. The aerial oxidation in such a solution is to the ascorbate and its product is acidic, but the acidity is minimized by the buffering action of the borax. A liter of working strength, reusable developer can be made from 0.8 grams of phenidone, 10 grams of sodium ascorbate and 10 grams of borax. Note that the phenidone is at half the strength of the original formula.