The hairs used for good quality oil paint brushes are stiffer and taper differently than the natural hairs used for watercolor. Where marten, horse, squirrel, ox, or goat hairs on watercolor brushes tend to be longer and more flexible, hog, boar, badger, weasel, and mongoose hairs are better for heavier-bodied oil paints. Let’s take a look at each one.
Kolinsky sable hair, especially female golden brown hair, is used for oil painting brushes. These hairs are slightly stiffer than the male’s tail hair and have better snap and resistance. In 2014, the true Kolinsky sable was banned from being imported into the U.S. Today, the Kolinsky sable actually comes from the Siberian weasel. The hairs are harvested from the tail of the males. This ban came about because sable martens, from which the pure red sable comes, do not do well in captivity. The only way to harvest the hair was through traps. Fortunately, that is now prohibited.
That’s good news and bad news for the artist. Well the little critters lives are saved, too bad these super high quality brushes are no longer available. But, the tail hair of the male Siberian weasel still makes a very fine and more affordable brush. Because manufacturers had stocks of Kolinsky saber, you may still occasionally be able to find some on the market. But when they’re gone, they’re gone. You will have to travel outside of the country to legally purchase them, as the ban was only for export to the US.
Pig bristles. These are by far the best hairs for oil paint brushes. They hold a good paint load. They spread the paint evenly. They blend the paint well. The best bristles come from pigs in the Chunking region of China. On the best quality brushes, the bristles are arranged in an interlocking fashion with the bristles curving inward. The hog bristles naturally part at the ends and are arranged so they hold paint well and spread it well. Cheaper bristles will have stiffer hairs, be arranged more erratically, and can twist both in and out, making the brush look fuzzy.
Horse or pony hair is commonly used in cheaper natural hair brushes and is marketed for different types of paint. Although they are sometimes sold as oil painting brushes, they are better for acrylics and watercolors, but are used more in student brushes and cosmetics. In terms of cost, they are cheaper than chipmunks.
Badger hair, because its shape is thinner at the root and thicker at the tip, makes for a bushier brush. Oil painters like these to mix.
The weasel and a close relative, the fitch, are very tough-haired with long cones. Although they are similar in quality to red sable, they are not as flexible, making them better for oils than watercolors.
Mongoose hair is strong and resistant with a good point. But they are better for oil paints for this reason, as they are not fine enough for watercolors. Sometimes they are hard to find.
There are a number of synthetics on the market under various brand names that are designed for oils and acrylics. As with natural hair brushes, you should try them out until you find one that fits your style of painting and you feel it in your hand. From a cost standpoint, synthetics are less expensive. You can see many of these brushes, natural and synthetic, and touch them before you buy them, at better quality art supply stores.
The best brands that are easy to find are Winsor & Newton, Grumbacher, Princeton, Simmons, and Liquitex to name a few.
One last tip: brushes will last longer if you always pull, never push, the brush across the paint surface.