Re: How many gum layers (Re: ferri sesquichlorati)
" Otherwise, why not just start with an image, invert it and make a negative of any unknown density without a curve and keep fiddling with it until you get what you want in the print."
Well, indeed, why not. Like Keith, this is exactly my approach and as Keith says, it works fine. And as Chris showed last week, it works good for her too. Her tricolor gum made from inverted uncurved channels was cyan-biased, but that's not a function of the curves, that's a function of the selectiion of pigment concentration of the three pigments in relation to each other. So I guess my answer to Mark's question "why not?" is, beats me! Seems like a perfectly reasonable approach to me.
But since Charles posted the link for ChartThrob yesterday, I've been playing around with generating curves some myself, and like Keith, I have to say, so far I like the "no curve" approach better too.
Recently, Mark, you said that a beginner could save a lot of time, money, and materials by investing in a system for generating curves, or better yet, two systems. At the time, that didn't make sense to me, because the time and materials you "waste" in the beginning learning to print gum are "wasted" in the process of learning to print gum, not in the process of generating negatives, and you still have to learn how to print gum, no matter how you generate your negatives. So I'm not sure how it would make any difference. And besides, the way gum works, there's very little waste; there's almost no print that can't be salvaged; pigment stain is the one exception, and curves or no curves don't have any bearing on pigment stain. But I didn't think there was any point in arguing further, so I let that thread die without saying so.
But now, after an evening of printing value templates, I have to say I think the savings are in the other direction; you save more materials by printing gum. At least when you're actually printing images, you have a print to work with and do something with, and chances are you can do something with it, even if you didn't get it "right" on the first printing. But a template of value patches is just a template of value patches. And if I was really going to do this, I'd have to do it for every single different pigment I ever use, at every concentration I use it at, at every environmental condition (humidity, particularly).... I would be doing nothing but printing templates for the rest of my life, and there's not a thing you can do with the stupid things, except generate curves. Talk about waste of materials! I'd rather be printing gum.
I can't say yet whether the resulting curves would be an improvement over the uncurved negatives; I'm not even there yet. Will report in due time with a comparison.
On Oct 25, 2006, at 9:27 AM, Keith Gerling wrote: