Until recently, I have always mixed my pigment/gum by eye. I know it
should look a certain shade, and the mixture should have a certain feel
when applied to the paper. Its just a physical thing that is hard to
explain. As I was recently running classes I had to be a little more
focussed, and provide some solid methods, measures etc. And that works
fine, but I think gum printing demands a willingness to try and see what
happens. Everything I have ever read about what gum printing is not, I
have found is in fact so. Its a contrary process that frustrates because
there are so many variables and even more ways to control them - yet
knowing all the controls doesn't necessarily a good gum print make. You
point out the importance of the look, the feel, the intuition of the
craft. I think this is ultimately the place we all want to be because we
are lead then by out own feelings rather than someone else's opinion. If
it works for you use it, otherwise don't.
Hamish