----- Original Message -----
From: "Anthony Farr" <
Subject: Re: XTOL and bubbles
> Juan,
>
> If you're already giving the tank a good tap on the bench,
especially
> when the developer is first put in, then air bells might not
be your
> problem. Air bells will give you small discs of less or no
density, but
> you say you're getting dots. It could be insufficient
agitation in the
> first minute of fixing, especially if the stop bath is
inactive. The
> action of alkaline developer and acid fixer produces some
gaseous
> by-products inside the emulsion. With too little agitation to
disperse
> the gas the emulsion can rupture at that point and a small
pinhole is
> left which will print as a dark spot.
>
> Just a possibility.
This is an interesting possibility. I am not at all familiar
with X-Tol, does anyone know the PH of the working solution? I
have witnessed the gas release from prints in too strong a
stopbath solution (it happens irregardless of agitation if the
stop bath is too strong).
Perhaps either a more dilute stopbath, or as Bob suggests, a
water rinse might correct the situation. The problem with using
a water rinse instead of stopbath is that development is stopped
by dilution of the developer, rather than by the immediacy of a
chemical reaction. This is far less predictable than a pre rinse
to stop air bells.
Note to Shel: The threshhold for chemical saturation in
prerinsed emulsion is 15 seconds, =/- 5 seconds. This is very
predictable. If it causes problems with your development times,
perhaps you are using too short a time with inversion
agitiation, or your agitation technique is not perfectly
repeatable from tank to tank.
In the Jobo, it is possible to use very short processing times,
in the range of 3 minutes, and still get perfect results. I have
used a prerinse for just about all of my processing over the
past couple of decades, and get perfectly preditable results.
William Robb
-
This message is from the Pentax-Discuss Mail List. To unsubscribe,
go to http://www.pdml.net and follow the directions. Don't forget to
visit the Pentax Users' Gallery at http://pug.komkon.org .
