From: Sandy King (sanking@hubcap.clemson.edu)
Date: 07/20/01-08:02:44 AM Z
My understanding is that the Jobo rotation is such that it imparts
not only a horizontal rotation to the developing tubes but that the
tubes also oscillate on a vertical axis enough to eliminate the
effects of bromide drag. So, in short I think you have nothing to
worry about in this regards.
As film develops bromide is released from the emulsion. If the
rotation of agitation is only in one direction ( or around a central
axis) the excess bromide produced locally will produce uneven
development, usually streaks of greater density with rotation
processing, around this area. Vigorous agitation breaks up the local
concentration of bromide and distributes it over the entire surface
of the film.
Sandy King
> >Sandy King wrote:
>
>>Also, when developing film on motor bases like the >Beseler or
>>Unicolor bases you should remove the tube >from the motor every
>>couple of minutes and give it >about 10-15 seconds of up and down
>>agitation, >otherwise the constant agitation fore and aft
>>will >cause bromide drag.
>
>Sandy,
>
>Perhaps this has been discussed earlier. Can you explain what
>bromide drag is? I use a Jobo CPP-2 which rotates in one direction
>about 1 and a half turns, then stops and rotates in the other
>direction about 1 and a half turns and repeats the cycle. Would
>this action help to eliminate bromide drag? I don't think I have
>ever had a problem with a negative that would have been
>related to something like bromide drag. But I would like to
>understand the issue better.
>
>Jim
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