From: Judy Seigel (jseigel@panix.com)
Date: 11/11/01-12:45:53 AM Z
On Sat, 10 Nov 2001, Sandy King wrote:
> The number of steps visible on a printed step-wedge is not a safe
> guide to speed. For example, you may have 18 steps discrete steps
> visible, but no maximum density. Lacking information about the first
> maximum black, what do you know about speed?
In gum printing "maximum black" is a function of the ratio of pigment
added. Period. Trust me on that.
That is, if you add enough pigment, you'll have maximum black, tho
probably a very short scale, as I've mentioned many times. However if you
give an EXTREMELY long exposure, and then a long soak, you can get the
scale longer, as the blocked up shadows wash off... assuming top tones
don't wash off at same time.... Which is to say the "speed" is a function
of the emulsion/exposure/development... and not .... whatever it was we
were talking about.
> ...I test with the stock solutions that I use to
> replenish, and these solutions are kept topped off. I top off the
> working solution with the stock solution, then add back to the stock
> as necessary.
Sandy, you'll have to explain that to a mere gum printer -- I can't follow
it, but it does sound like you're testing with new solutions. Plus, if you
top off working solution with stock solution, I don't see how you can tell
diddle, since the concentration would be indeterminate...
> Concentration of our solutions is in fact very different. My stock
> solutions range from 1/4 % to 6%, much less than the 27% you describe.
I usually print with in effect 10 to 12% solution, but still at least
twice your strength... Also, as per my reply to Katharine... I don't think
the processes are so much alike. The gelatin for instance is the crux in
carbon, may not even be present in gum.
Etc.
Judy
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