Joe and Yves
I have still not looked back in the list archives to find the references
mentioned by Christina. Herself, Judy, and Mike Ware discussed
this reversal effect some time ago. I remember the fact, but not what
has been said then.
In the meantime, please consider the whole series of tests that I made
with lampblack (yesterday I posted only half):
http://usuarios.arsystel.com/tksobota/Lampblack_strip2.jpg
The handwritten number at the bottom of each strip are the minutes
I exposed it. The linearity between 10' and 30' catches the eye, eh?
You see that steps 15 and 16 of the 30' strip are clear. They have
received 30 minutes of exposition. The same steps 15 and 16 in the
5' strip show the reversal effect, even as this strip has received the least
exposition.
In my opinion, if heat were the culprit, the effect would be reversed.
BTW, Yves, in case you did not notice, I had put the word 'solarization'
between quotes, just to let anybody know that I was perfectly aware of
its possibly incorrect use in this context.
Tom
At 17:27 03/12/2005, you wrote:
> >>> tsobota@teleline.es 12/03/05 5:36 AM >>>
> >>...
>Have a look at this test strip, printed with lampblack (0.03g in 2cc
>gum solution + 2cc Amm.Dichromate 30%, paper twice sized
>with gelatine)
>http://usuarios.arsystel.com/tksobota/Lampblack_strip.jpg
><<
>
>Well raise my rent! There it is again. Thanks for the confirmation Tom
>and Judy.
>
>I'm wondering if it may also be some sort of heat effect since it
>happens under dense areas of the negative? (Like, dense areas capture
>and retain heat more at a certain opacity essentially cooking those
>areas underneath and trapping some pigment in heat-hardened gum???)
>
>Probably another good reason to keep gum negatives on the thin, low
>contrast side, minimize exposures, and build density through several
>layers rather than trying to do it one-shot.
>
>Joe
Received on Sat Dec 3 13:17:07 2005
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