Phenidone-C Developers - I've Learned A Few Things

I've been tweaking my phenidone/c developers recently and learned a few interesting things so I thought I would share.  Here are some quick points:

1. The amount of phenidone is directly proportional to developer activity.  Using PCB (19g borax + 6g ascorbic acid + 0.15g phenidone + water to 1L) as an example, reducing the phenidone from 0.15g/L to 0.1g/L makes a huge difference in developer activity.
2. The more phendone/c you have, the lower pH you need for active development.  I discovered that with enough phenidone/c you can have very active development at a pH of 7.2.  On the other extreme, you can use ridiculously small quantities of phenidone/c (e.g. PCM uses 0.8g/L ascorbic acid +  0.02g/L phenidone) but increase pH for similar activity.  This means you can adjust the activity of phenidone/c developers either by varying the pH or the amount of ingredients.
3. More vit-c doesn't make much difference in activity but does extend shelf life.  For example, using ascorbic acid at 4g/L vs 8g/L shows no discernable difference in activity but makes a re-usable developer last longer.
4. pH does not affect grain very much.  Grain from developers at pH 8.4 and 9.6 look very similar.  This is based on observations with a scanner and RC prints.
5. Stand development doesn't work the way we think.  Testing showed no significant difference between full stand development (60s initial continuous only) vs minimal agitation (60s initial continuous, 10s every 5 mins) except for time when using a very dilute developer (PCM).  Agitation more frequent than 5 mins showed more highlight development and increased contrast.
6. You really don't need much potassium bromide.  Even without potassium bromide, fog is minimal (most won't notice it), but adding 0.04g/L clears it up with no effect on developer activity.

If you like to concoct developers as I do I hope you find this useful.

MM