Watercolor Brush: Synthetic or Natural?

Artists use brushes for many purposes–to paint, certainly, but also for applying glue, frisket (a removable masking fluid), ink, varnish, or sealant. Brushes are also good for removing eraser dust, glitter, cat hair, and the occasional cookie crumb that finds its way onto canvas, paper, or journal.

The confusing information about brushes is the number associated with their size. Flat brushes are measured by the width at the ferrule, and that logic makes it easy to guess how large the brush it.

The synthetic brush (black handle, top) holds considerably less water than the smaller squirrel-hair brush.

Round brushes measure from 0 to 24, with 0 being the smallest in the group. They also go below zero, with 0000 being smaller than 00.

Mop brushes are numbered with the same system, but the size of the brush doesn’t equal the size of the round brush. This can be a head-scratcher if you are new to buying brushes.

Tip:  A typical squirrel mop #0 equates to a #10 round; a mop #6 is the equivalent to a #16 round, and so on.

Tip: Genuine hair brushes (from kolinsky sable, red sable, fox, squirrel to ox and goat ) use real hair from the animal, (generally the tail). Real hair has ridges and scales and holds water better than smooth synthetic brushes. Natural brushes are also “springier” which means they recover their shape better while in use. Natural  brushes are more expensive than synthetic brushes. Often, much more expensive.

Tip: For watercolor, which demands loading with lots of color and water while retaining a good point, use a natural-bristle brush.

Tip: Acrylic paints are alkaline and wear out natural-hair brushes faster than synthetic brushes.

Here is why the natural-hair brush is worth the extra price when you are painting with watercolor–the “fatness” of a synthetic brush doesn’t tell you how much water it will hold. So I did an experiment.

I put all three brushes into water. (I tinted the water blue to make it show up on the photo.) You’ll notice I didn’t just drop them into a jar. Natural-hair brushes shouldn’t be left point down to soak. It ruins the point. And once a natural-hair brush has a bent tip, it’s ruined.  Wet, the two larger brushes look about the same size.

The synthetic brush (black handle, top) holds considerably less water than the smaller squirrel-hair brush.

I then pulled each brush straight out of the water, allowed the water to stop dripping, then squeezed each brush over a napkin. The wet ring shows how much water each brush held. The synthetic brush (black handle, above, top) sheds water as you pull it out of the bottle. The smooth fibers don’t hold water like the scale on the hair of the natural-bristle brushes. The natural brushes hold more water.

The water-ring of the synthetic brush is smaller than the water-ring of the smaller of the two squirrel brushes. It’s a big difference; when you are loading your brush with color and water, use the biggest brush for the work. For my money, I prefer natural-hair brushes.

Tip: A cheap brush doesn’t save you money. You will spend more time working with them. They often shed hair on your surface, and that’s difficult to pick out without disturbing the paint or surface.

More information on brush material and sizes.

Quinn McDonald is discovering a certain joy in using watercolors and watercolor brushes for their lack of control.