MERITOL SUPERFINE GRAIN DEVELOPERS
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
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Development times @ 20°C
(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.
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