From: Sandy King (sanking@clemson.edu)
Date: 02/05/02-07:10:52 PM Z
Ed,
The problem is not that I can not increase contrast by adding
potassium dichromate to the sensitizer, but that doing so causes a
significant drop in printing speed, and a grainer look.
On the other hand, with traditional kallitype (ferric oxalate) I can
get nearly perfect control of contrast over a wide range with no
increase in grain by varying the amount of dichromate in the
developer from 4ml per 1000ml of developer up to 32ml per liter. This
allows me to print negatives with density ranges varying from a lot
of about 1.2 up to a high of 2.25 with little loss of printing speed.
Sandy
>Sandy,
> In my limited experience, adding 1 or 2 drops of 3% potassium
>dichromate definitely gives more contrast, though I often have more problems
>with defects in the emulsion--I'm still trying to figure out if I'm just
>being sloppy in preparing the sensitizer, or if it is dicey no matter what
>you do What kind of problems have you had? What concentration is your pot.
>dichromate? One of the best prints I made came when I used 2 drops of 3%
>pot. dichromate on the first coat, then dryed, then used straight sensitizer
>for the second coat. There was some mention at APIS that sodium
>hexachloroplatinate might help increase contrast for VDB, but I haven't had
>a chance to pursue it yet.
>Ed Buffaloe
>http://unblinkingeye.com
>
>----- Original Message -----
>From: "Sandy King" <sanking@CLEMSON.EDU>
>To: <alt-photo-process-l@sask.usask.ca>
>Sent: Tuesday, February 05, 2002 10:16 AM
>Subject: Another VanDyke question
>
>
>> If someone knows of an effective way to control contrast with
>> vandyke. My tests in adding potassium dichromate to the sensitizer
>> before coating and/or to the developing water have all resulted in
>> mixed results. Are there other options?
>>
>>
>> Sandy King
>>
>>
>>
>>
>>
>> --
>>
--
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