[Leica] development

["Rod Fleming" <rodfleming@sol.co.uk>]

Hi

Chris asked


>.  Does prewet mean that you can
>reduce the developing time?

No. Think about it; if you presoak you saturate the emulsion with plain
water. When you immerse the film in the dev, it takes a small period of time
for the developer in the concentrated developer solution to diffuse into the
water contained in the wet film and begin to react.

When you plunge a dry film directly into the dev the dev laden fluid soaks
straight into the emulsion; it will begin to react almost immediately.

I doubt if it makes a lot of difference, though.

(This is all very different from "water-bath" development BTW.)

The instructions for some rotary tube processors- like my Jobo- suggest
using a presoak, but I think this is more to do with stabilising the
temperature of drum, spiral and film. After a lot of experiment, I've
dispensed with the step altogether.  It seems to make no difference whatever
to the required dev time, even when measured using step wedges and a
densitometer.

I think one factor- the equalised temp- is being cancelled out by the other-
the need for the developer to diffuse into the emulsion. But that's only a
hunch- perhaps there aresome phyisicists out there who could she light?


Cheers


Rod