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Re: sumi ink for gum



kgerling@ameritech.net writes:

> The paper was sized with gelatin and hardened in glyoxal.  The tests were
>  made with 21 steps. Yes, Judy, the stain is actually worse in areas of less
>  exposure.

Hi Keith,

My "theory" is that during coating, the emulsion has a chance to blend with 
or to soften the gelatin a little. In the highlight where some exposure is 
received, the top layer is exposed and hardened. During development, the 
exposed layer washes out and at the same time pulls the bottom layer away. In 
the highlight where very less or no exposure is received, no top layer is 
hardened, so this pulling-away action is not happening, thus it stains. This 
is, of course, just a theory. If you are interested, you can see my 
explanation in the archive,  search under "gelatin" and "hardening." Sorry 
that I don't remember the exact title (subject line).

This solarization (staining on no-exposure region) happens more if your 
gelatin is not strongly hardened or if your emulsion is watery.

If your negative does not have a very-high density area (like specular 
highlight), then you probably won't see the solarization effect at all 
because all area will receive some exposure. In any case, a short flashing 
will take care of the solarization effect since now the whole image receive 
some exposure (a longer flash, if calculated properly, extend the scale; but 
that's a different effect).

That is assuming your paper has reasonable sizing. If the pigment has 
penetrated into the fiber (as in unsized paper), then it is very difficult, 
if possible at all, to clear the stain.


Dave Soemarko

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