The secret of gum arabic

Q. I’ve seen some lovely paintings in which gum arabic is used in conjunction with watercolor. The colors are so vibrant! How would you use it? Is there a special technique for combining the two?

A. Gum arabic is the binder in which the pigments are dispersed to make the watercolor paints, so its use in the course of making a painting is akin to using an oil painting medium containing linseed oil with oil paints. Adding gum arabic to paints will have several effects: It will slightly extend the drying time of the paint, it will make the colors seem more vibrant and transparent, and it will increase the gloss of the dried painting.

You can use this substance in two ways: Add it to individual colors as you’re mixing them, or add it to the water that you’re mixing with your paints. In the first instance, pour some of the gum into a small dish to avoid contaminating the stock jar, then dip your brush in the gum and add that to the color-and-water mixture on your palette. Its addition will affect only those colors you’re mixing. In the second instance, add a small amount to your mixing water; the addition will affect all the colors you mix.

It’s hard to be precise about how much to add, since it depends upon whether you’re making large pictures or small ones, how much paint you’re using, and how big a jar of mixing water you have. You’re going to have to experiment. When you do your tests, be sure to keep this in mind: The layers of paints containing extra gum arabic should be as thin and transparent as normal watercolor paints. Too thick an application of the gum will make the paints quite brittle.

Nationally respected artist Kevin Macpherson is based in Taos, New Mexico.

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