Gene, a friend pointed out a mistake in what I wrote about adding phenidone. For your stock solution dissolved in alcohol, you want to use 0.1g/100ml, which is a 0.1% solution. Then, when you add it to your developer, use 10ml / 1L of *working* solution, or 0.01g phenidone / working liter. Sorry for the confusion.(posted 8262 days ago)