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Johnsons Super Fine Grain Meritol Formulae

Super Fine Grain Developer
Meritol 16 g


9 g
    Paraphenylene diamine 7 g
Sodium Sulphite (anh)     90 g
Water to     1 litre
Meritol-Metol Developer      
Meritol 13.7


7.7 g
    Paraphenylene diamine 6 g
Metol     2.3 g
Sodium Sulphite (anh)     90g
Water to     1 litre
M.C.M. 100 Developer      
Meritol 16 g


9 g
    Paraphenylene diamine 7
Sodium Sulphite (anh)     88 g
Tribasic sodium phosphate (anh)     2.9 g
Borax     2.3 g
Potassium Bromide     0.25 g
Water to     1 litre
Meritol is no longer manufactured but may be substituted by Pyrocatechin and Paraphenylene diamine (PPD) as suggested by Edmund Lowe.


All developers containing Johnson's Meritol rank as superfine grain types, although grain size varies slightly according to the composition of individual formulae.

Super Fine Grain Developer:
Containing Meritol and sodium sulphite only, confers the finest grain of the group and requires sensitive materials to receive about 50 per cent. more than normal exposure, although in the case of under-exposure quite good results can be obtained by longer development which does not materially increase grain size.

Meritol-Metol: As with Super Fine Grain Developer, this formula requires that sensitive materials shall have about 50 per cent. more exposure than normal, but the chief advantage of Meritol-Metol is its rapidity, development times for which are only half those of above.

M.C.M. 100: As introduced by the Miniature Camera Magazine, this formula combines exceptionally fine grain with good developing speed which is midway between Super Fine grain and Merito-Metol. It gives high threshold expression and requires no increase over normal exposure. Under-exposures are satisfactorily dealt with by increased developing times.

Important Note: It is emphasised that the backing on certain roll films has a restraining effect on Meritol development, hence such films should be given a preliminary soaking in plain water for about three minutes with agitation. This treatment does not affect development times.

Notes adapted from the British Journal Photographic Almanac 1954


Development times @ 20C
(These are approximate based on the times given for FP3, HP3 and Pan F)

Super Fine Grain Developer: 14 - 18 minutes

Meritol-Metol Developer: 7 - 9 minutes

M.C.M. 100: 12-17 minutes

The developing agent Meritol is a fusion complex of Paraphenylene Diamene and Pyrocatechin. It can be made in laboratory conditions but requires heating, both chemicals are toxic.