>Nine (9) 1X5" strips of carbon tissue were sensitized in two sessions, using
>five separate 5X7 trays. Easy was sensitized separately, using 3 ounces
^^^^^
Each?
>of fresh sensitizer, for 3 minutes. The nine strips were dried
>together. Each was labeled before sensitizing according to intended use.
> >
>> > b) The same batch of carbon tissue was used for
>> > all tests. This was a warm brown tissue made=20
>> > from 3 parts Carmine Crimson, 4 parts Brown, 3
>> > parts Primary Yellow, and 2 parts Sumi Ink=20
>> > concentrate.
>>
>> This is a fairly low contrast color to start with.
>>
>My experience with this tissue is that it is fairly high in contrast. After
>all, that is 12 grams of pigment per 1000 ml of coating solution, including
That is a rather significant part of the equation you left out! What
percentage of gelatin in there, at what Bloom Index?
>two grams of very strong Sumi Ink concentrate. Still, the color does
>introduce a variable that could have been eliminated by the use of a
>nuetral black tissue.
The color is important indeed and even "neutral black" has to be defined.
At one point I had 17 different types of black pigment in my atelier here.
They varied tremendously in terms of characteristics.
Another very important variable is the thickness of the coating. Pretty
hard to judge with hand coated techniques.
>This is what I did. After the 9 strips were dry I put three each in
>a ziplock bag and froze, in anticipation of running essentially three
>exposures. What I failed to mention was that each set of exposures
>involved three strip simultaneously on three separate Kodak #2 step
>tablets. This introudes one variable I failed to mention, however
>before exposure I measured steps 1, 10 and 20 of each step tablet and
>there was no difference greater than .04 which I believe to be of
>no consequence. Thus, the first set was exposed soon after the tissue
>was dry, and the other two sets were done at intervals of about
>one hour, but with tissue frozen during the interval.
It is still another variable, although probably not enough to jeopardize
the value of the test.
>> >2) When the tissue is sensitized with dichromate solutions of 1% or more =
>> >there is a strong suggestion that a combination of UV and Cool White tube=
>> >s is more effective than either along. I have conducted some further test=
>> ^^^^^^^^^^^
..
>> Most definitely, which is why I seldom used less than 2%. The sensitizing
>> time is also very important; perhaps more when dealing with weak
>> concentrations. This said, I don't see how the latter part of your
>> statement affects the previous part.
>>
>>
>Understood, the latter part is an observation based on past experience, which
>is not demonstrated in these tests.
Ah! I knew there were pieces of the puzzle missing;-)
>BTW, I have long been curious why my sensitizing solutions with 350na tubes
>seem to be so different (requiring such low percentages to achieve
>good contrast) from what is described in the literature. Do you have
>any knowledge of others actually working in carbon with these or similar
>tubes? I would be very interested in knowing what kind of strength
>sensitizer they find effective.
I never used those and don't know of anyone who is with carbon transfer.
Also, carbon being one of the more difficult processes, one has to be
careful, as you probably know, when reading someone else's data. The many
variables are such that it is difficult for the beginner or the casual
experimenter to really tell you what is going on.
Luis Nadeau
awef6t@mi.net
Fredericton, New Brunswick, Canada
http://www.micronet.fr/~deriencg/nadeau.html