Continued from Hand-mulling Paint, Part I.
If you’re mulling a particular pigment for the first time, you won’t know just how much oil you should add. You can do some research online, something like “raw umber oil absorbtion” – but you don’t really need this information to begin. At first, use less oil than you think you will need. Many pigments (not all) will loosen and become more and more oily as you mull. I try to add just enough oil to pigment so that when I start mixing with a spatula, I’m pretty sure it won’t be enough oil. Then I start mulling. Often it winds up being enough after all. Once you’ve done this, you can keep notes on how much oil to add to each pigment.
You’ll go in a big circular motion with the muller, and pretty soon you’ll have to stop, grab the paint spatula, and scrape the paint together into a pile again. You’ll have to scrape paint off the sides of the muller as well. Make it into a pile and start mulling again. It helps to switch hands every so often. It can take a tiring amount of time with some pigments, and patience is sometimes required. After a while, you’ll know if you need to add more oil (or, sometimes, more pigment).
Below, I’m mulling and then scraping together a homemade copper green pigment into linseed oil:
Just how necessary is it to mull pigment? Why can’t you just mix the stuff up on the palette with a spatula and go? Well, sometimes this might work – the homemade candle black I made into an oil paint recently barely required mulling at all, and probably could have been used right after mixing it with oil – but other times, mulling is absolutely required. See the difference between mulling or not mulling Egyptian blue, below:
The first swatch is unmulled. It was quite difficult to even brush it out: I had to add extra oil and use one of my stiffer bristle brushes to manage it. The second swatch is after perhaps only two minutes of mulling. Big difference, isn’t it? The third swatch is the mulled Egyptian blue mixed with some zinc white. Nice color, huh?
Some earth pigments are said to display their best colors when only lightly mulled, and that this is one problem with the uniform grind of modern, industrially-produced pigments. I thought that I was seeing this phenomenon when I was grinding up a nice raw sienna from Sinopia Pigments. The more I mulled, the duller the color seemed to get. See the pic below, the difference between those two piles of paint? I thought I was seeing over-grinding in action. However, I was wrong: it was just that the finer clumps of pigment were soaking up more of the oil. When I added more oil back into the paint, its color sprang to life again. So if that happens to you, try the same.
I’ll post one more installment of the Hand-mulling Paint series, and discuss tubing your own mulled paint.