The
main reason for inverting the developing tank
is to make sure that the film gets equal treatment in the
developer. One of the best ways of achieving this is to tumble the
tank by turning it from end to end.
Why
do we agitate the tank?
The developer interacts with the emulsion
of the film. It vigorously attacks the silver it come into contact
with and becomes exhausted. By inverting the tank you refresh this
action, producing evenly developed negatives. It is
important
to get this right. To little agitation will allow by-products of the
process to build up, leaving pale-toned streamers as they slide to
the bottom of the tank. Likewise excessive inversions will produce
currents in the developer, creating uneven development. Most process
times allow for agitation.
Once the developer is added you
should agitate the tank for the first thirty seconds but before you
put the tank down give it a slight twist and tap it on a hard surface
( it is a good idea to lay a soft towel down so you do not damage the
tank) so you dislodge any air bells/bubbles that may have attached
themselves to the film. Then you need to agitate for ten seconds in
every minute of the process time about four inversion per ten seconds
or as the developer manufacturers instruction advise. For example PMK
Pyro recommend one inversion every fifteen seconds.
I have used this inversion method
from the start of my developing career ( no pun intended) and has
produced consistent results every time. Once you have found a method
that works for you; you should stick to it.
