Re: Tonal inversion (was (Gum) Tonal scale)

Joe,

This 'solarization' happens, I have seen it mostly with blacks under
high density areas of the negative. But sometimes with other colors too.

Years back I was using x-ray film, which was double coated and had
a very high D-Max and this value inversion happened frequently.

It was driving me crazy so I stopped using x-ray film which was
a very good idea...

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

I have exaggerated somewhat the contrast so the effect is
easier to see. In the original, all the steps of the three strips
are distinctly visible and separated.

I have no explanation for this effect, but I think that it has
been mentioned on this list some time back.

Your idea about the muddied water and pigment migrating
could be perhaps tested developing a test strip under slowly
running water, instead of the usual 'stand' developing.

Tom

At 02:42 03/12/2005, you wrote:
>No big surprises here except the curious response of the Bone Black
>pigment test (bottom middle). Take a look at the circles around the
>numbers and step areas 14 and higher. There is definite pigment stain
>in those areas which should be paper white. It is as if there is a sort
>of pigment stain solarization effect happening. Steps are
>differentiated from about step 6 through step 13 and then the steps
>print darker due to pigment stain. I speculating that a very small
>amount of exposure has caused steps 12 & 13 to print almost paper white.
> I'm thinking the slightly exposed gum there has reduced pigment
>staining which perhaps has occurred during wet processing. IOW, as the
>prints autodevelop in water, this particular pigment is released from
>all areas of the print to some degree and it muddies the water. Where
>an exposure hasn't had any effect at all, the pigment migrates to the
>unprotected paper and stains it. This is only happening under the gum
>though. Areas outside the coating remain unstained and protected by the
>gelatin size. Somehow the emulsion has caused the areas beneath to
>stain disproportionately, perhaps by adversely affecting the sizing or
>somehow interacting with it and weakening it. Has anyone else seen this
>before or have an alternate theory of why it has occurred?
>Joe
Received on Sat Dec 3 04:36:30 2005