U of S | Mailing List Archive | alt-photo-process-l | Re: Miracle size for gum

Re: Miracle size for gum

----- Original Message ----- From: "Judy Seigel" <jseigel@panix.com>
Sometimes I have trouble staying out of an argument, because who doesn't love a good argument? Research shows, moreover, that an argument about gum firms the skin and makes the hormones flow, while discouraging outsiders from attempts to muscle in on the process. But the gum argument (or "discussion") I'm staying out of now is because I don't know what the hell folks are talking about & decline to expose my ignorance.
I hear ya, I hear ya...I agree in that testing and arguing about gum doesn't get gum printers or gum prints made. The proof in the validity of gum testing comes in the work produced, IMHO. Now, that will open another can of worms--what constitutes a "good" gum print and I daren't touch that with a ten foot pole. But there are a lot of excellent gummists who never pick up a step wedge. They just make prints.

I find it extremely useful that when we discuss things as tonal range, miracle size, more or less dichromate, more or less exposure, etc. we find a way to talk apples to apples in gum, and that is where the lowly step wedge comes into play for me--scientific or not, used and discussed correctly or not (thanks, Etienne).

Thus when a statement is made that such and such produces a longer tonal range, I take it to mean that the maximum "black" for that color pigment has been reached (obviously not black as in a glossy silver gelatin) as well as paper white has been achieved, and those steps in between can be counted and compared to get somewhat close to apples to apples. Either the step wedge shows just a few steps, or lots of steps. And each step on the step wedge, being film, is a difference of 1/3 stop or 1/2 stop that corresponds to increasing or decreasing hardening of gum, whether that hardening equates or not to a measurable log of density.

When gum gets a bad rap as being a "two stop process" which, I assume, the writer meant there were only 4 **steps** of color on the step wedge or 6 on a 31 step (writer is well known, and certainly gum has a reputation of being a short scale process), then it is important to discuss what kind of tonal range people who gum print frequently are getting. I personally don't find gum THAT short scale of a process. Certainly not as tonally long as platinum but long enough.

But as has been found in this discussion, as usual anything gum, the parameters of the testing is different from gummist to gummist and therefore no longer compares apples to apples anyway. And then we get into arguing over how many angels dance on the head of a pin.

And then it's interesting to see your advice come back to you--or not. Seems to me a while back on this list I dared to suggest that past a certain point more dichromate wasn't necessary--it didn't decrease exposure enough to warrant the extra amount and I settle now on an easy to measure 15% am di (used to use 7.5%, one list member only uses 2.5% and her exposures are not lengthy). That by a step wedge. Wow did I get creamed in that discussion.

Seems I also mentioned that using EQUAL strengths of ammonium, sodium, and potassium dichromate had different speeds--ammonium being the fastest, and for all the solubility that sodium has, it doesn't have much oomph--more like potassium at the same strength (used 10% for all). That I found by a step wedge. I know at least Sandy King corroborated and even gave a percentage comparison between am and pot di. Oh, and Kosar as well...but man, the first time I mentioned Kosar I was creamed.

So even though using a step wedge on a process that really isn't photographic in a sense (just photosensitive) and talking about it in photographic terms, that step wedge sure is a handy little thing...

OH, and having been cleaning out my dimroom all day, I finally found my motherlode of step wedges. I had lost them I thought permanently, and ordered 3 more 4x5s and 1 8x10, and NOW I have a passelode of the things, heheheheh. I just love this cleaning thing. For some reason I had put them under a towel on top of which I let gum prints dry before exposure.

Back to size, Marek, I am going to run right out and buy that miracle size, lemmetellya. If I could find a nontoxic size that also printed a LONG TONAL RANGE (gasp) I will personally come down to TX and kiss your cheeks!! And Jeremy Moore, that video thing is a great idea to do for the list! Good discussion...


Christina Z. Anderson