Metol / HQ ratio

[lensmagic]

I looked in Mason, Photographic Processing Chemistry (1966), and at page 133 in a discussion of Phenidone versus Metol found that for the Metol/Hydroquinone mixture the optimum molar ratio is between 22:78 and 28:72, giving a mean weight ratio of 1:1.6, but that the ratio usually used is a little lower than this, ranging from 1:2 to 1:4. Okay, why a lower ratio is used is not explained. Maybe someone here on APUG knows.

 

[Gerald C Koch]

OK, I defer... with sodium hydroxide (ouch!) HQ does, indeed, 'take off'. - David Lyga

For the past decade or so I have been using my corrected version of Kalogen.1,2,3 This is an MQ developer but made like Rodinal and the developing agents exist as phenolates. At a dilution of 1+49 it yields a development time ot 8 to 12 minutes. So David is right.

1 Kalogen was marketed commercially from 1917 to 1918. It was devised by Paul L Annderson to replace Rodinal which was not available in the US during WWI.
2 William Snyder Dignan Newsletter, August 1973.
3 Mr Snyder in the Dignan article had modified the original formula and changed the MQ ratio from 1:2 to 1:4. However the amount of sodium hydroxide was almost twice what was needed to produce the pnenolates resulting in a developer that was very rapid in its action but had very poor keeping properties.