Archived posting to the Leica Users Group, 1998/11/05

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Subject: Re: [Leica] PRE WASH?
From: Scott Busby <reconair@primenet.com>
Date: Thu, 05 Nov 1998 19:22:09 -0700

Bob,

  Pre-washing or pre-soaking whichever you prefer IMHO, is a matter of
technique.  Ansel Adams describes in his book "The Negative" a pre-soak of roll
films for at least 30 seconds with agitation.  Seemingly, this is to remove
airbells.  Not much additional explanation accompanies this extract.  For me, I
do it for several reasons.  One to remove airbells as described, but to also to
bring the film itself to developer temperature and ensure an even dispersal of
developer over the film's surface.  Certainly, this seems unnecessary, but for
those of us who require absolute accuracy in film development it is essential
if only for the confidence factor.  Scientifically, there seems to be no real
reason for doing it.  Your argument is valid based on your experience and the
physics of it all will back you up.  But, we all have our little quirks.

Scott Busby

Bob_Maxey@mtn.3com.com wrote:

> Concerning the comments about prewash of film before development. Would all
> of you who advocate this and those who are posting reasons why or why this
> is or is not a good idea, please provide some sources for your information?
> Additionally, which specific films are you talking about, or are you saying
> the reasons are a general rule of thumb.
>
> 20 years of daily processing, of every conceivable film, in roll and sheet,
> including Minox, 110 sizes, Cirkit, Aerial and Banquet, perhaps 30,000 or
> more rolls so far, in deep tanks, roll film tanks and troughs do not
> indicate these problems of how fast developers work with wet Vs dry
> materials. I would like to see substantive proof  that it makes a
> difference. I tested this idea more than a decade ago with different
> emulsions and I saw no evidence that there is any concern.
>
> The last test was to eliminate air bells when the burst system went down,
> and pre wetting was one solution to eliminate the problem. Absolutely no
> substantial difference in negative density either way. It was not generally
> reported in the literature and I wonder. Perhaps it might be happening to
> some, but it may also be something else altogether.
>
> The only film I pre wet these days is litho materials that I use for making
> presentation slides. Pre wetting helps eliminate the air bells to some
> extent.
>
> RM