From: Sandy King (sanking@hubcap.clemson.edu)
Date: 03/01/01-08:29:14 PM Z
Carl,
I was surprised by the TXT times in comparison to HP5+ as well, and it may
well be caused by the outdated film, or a slow response to
pyrocatechin.However, I tested two different TXT films, one from 5X7 stock,
another cut from 12X20 film, and am pretty sure about the validity of the
testing method and the results.
Just for the record, my film testing method is as follows. First, I
expose 5 sheets of film to a Stouffer 4x5 step wedge by contact printing
(using my enlager as a light source, with a 80A filter). Exposures are
timed with a Metrolux which is accurate to 1/100 of a second. I then
develop the films at 72F in tubes with constant rotation, each sheet for a
different time, using 150ml of devleoper per 5X7 film (or the equivalent
with other films). In the case of most of the films mentioned the times
were 6,9,12,15 and 20 minutes. I then read the densities with the blue
filter of a transmission densitometer and plot the results with Phil Davis'
plotter program.
Sandy
>Sandy,
>
>A quick caution on the TXT times. Gordon Hutchings also in his PMK book
>shows TXT requiring longer development than HP5-Plus, but I have never
>encountered this, with any developer, any agitation technique, or any
>desired final contrast range. I always find HP5 to require anywhere from 25%
>to 75% longer development than TXT to achieve similar contrast. Perhaps TXT
>has a sluggish response to pyrocat, but the outdated material may have
>skewed this particular result.
>
>But it's great to have the starting test times for all these combinations,
>thanks for posting them.---Carl
>--
>
>----------
>>From: Sandy King <sanking@hubcap.clemson.edu>
>
>> 2. For combo printing with silver + pt/pd -- Use a 2:2:100 dilution and
>> develop for the following times for a DR of approximately 1.4, when
>> subject luminance range is about 7.
>> BPF 7 minutes at 72F
>> HP5+ 9 minutes at 72F
>> TXT 10 minutes at 72F
>> FP4+ 6 minutes at 72F
>>
>> 3. For alternative printing only for a DR of approximately 1.6, use the
>> 2:2:100 dilution and develop as follows.
>>
>> BPF 11 minutes at 72F
>> HP5+ 13 minutes at 72F
>> TXT 20 minutes at 72F
>> FP4+ 10 minutes at 72F
>>
>> Development based on rotary processing in tubes with continuous agitation.
>> Times are only guides. TXT times in particular may be suspect because the
>> film tested was outdated, though still with a very low B+F.
>>
>> Sandy King
>>
>>
>>
>>
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