Re: pH meter

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From: Sandy King (sanking@clemson.edu)
Date: 10/17/03-09:31:52 AM Z


I am going to add my two cents worth to this issue.

The original question was, "Can anyone comment on the relative merits
of using a pH meter in general photographic practice? Dick Stevens
more or less swears by it for fine-tune controlling of general
photographic practice and especially for hand coated processes like
kallitype (I'm only recalling what I read, and that is likely poorly
remembered)."

I use a pH meter quite often in my testing of different developers.
All developers are designed to work best at a certain pH and the
ability to verify the pH is important because it serves as a check
that the developer is in good working condition. I also use the pH
meter from time to time to check on the condition of the dichromate
solutions I use in carbon printing, especially if I have had an
unexpected result and need to find out why.

As to the use of these meters in general photographic practice I
would have to say they rank pretty low and most people would do just
as well with the pH strips. With all due respect to Dick Stevens I
don't recall ever using the pH meter for testing any of the solutions
used in kallitype process, and I am a very good kallitype printer.

As to the issue of reliability, I have two small hand held pH meters
and both have worked fine for at least the past five years. Both are
made by Oaklon, and one is called the pHTestr 1, the other is called
the pH Wand. The Wand is more accurate and has a replaceable probe.
The meters have to be re-calibrated from time to time but otherwise
seem to have been pretty trouble free over the period of time
mentione. The Testr cost less than $100, the Wand about $150, and I
purchased both of them from Bryant Labs (now Bryant Laboratory) in
Berkeley, CA.

Sandy

>From: Greg Schmitz <gws1@columbia.edu>
>Subject: Re: pH meter
>Date: Fri, 17 Oct 2003 03:11:40 -0400 (EDT)
>
>> There's a lot of B.S. about pH measurement out there and
>[...]
>> FWIW I already know how pH is measured and the theory behind it.
>
>Didn't you just say that you didn't know about a very well known
>problem with pH measuring probes? Very amusing.
>
>Anyway, as a suggestion for Kris Erickson, I suggest to get an
>inexpensive refillable, double junction probe with a decent display
>unit. Still, like any pH meter, you need to calibrate the system at
>the beginning of each session or the reading won't be accurate (the
>probe voltage drifts a lot and this needs to be corrected each time).
>If this is too cumbersome, I recommend to get boxes of pH test strips
>-- it has limitations, but for typical darkroom use, fine step ones
>are quite decent, and they do not require calibration like pH meters
>do. There is no cheap, easy, maintenance free pH probe usable for
>darkroom solutions.
>
>--
>Ryuji Suzuki
>"Reality has always had too many heads." (Bob Dylan, Cold Irons Bound, 1997)


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