How to Use a Fan Brush to Blend Two Colours

Start with two values of the same colour butted up against each other, a light green and a dark green here. Do not try to blend them as you lay them down. You want a hard, obvious seam, because that seam is the thing you are about to learn to remove.

Work slightly wet. Acrylic that has skinned over will not move under a fan brush, and a fan brush pushed at dry paint just scratches at it. Oils give you far longer, which is why the fan brush has an older history in oil painting.

Take the clean fan brush and strike across the join at roughly 45 degrees. One direction, then back the other way, so the strokes cross each other over the boundary. That criss-cross is what pulls a little of each value into the other.

Do not stroke along the seam. Running parallel to the line just moves the line around. It has to be crossed, repeatedly, from both sides.

Choke right back to the end of the handle. Holding a fan brush up near the ferrule like a pencil gives you far too much control and far too much pressure, and heavy pressure is the one thing that ruins the effect.

The bristles should barely bend. You are dusting the surface, letting the tips do the work. If you can see the ferrule pushing the bristles out sideways, back off.

Work back and forth over the join, moving the brush a little further into each value as you go, until you cannot find the line any more. What was two blocks of colour is now one continuous run from light to dark.

Stand back every few passes. Blending is one of those jobs where six inches from the surface tells you nothing and six feet tells you everything.

Once the two-value gradient is working, bring in a third colour along one edge, a pale cream here. Lay it down as its own block again, hard edge and all. The blend comes after.

A much lighter value against a dark one is a harder blend than two neighbouring values. Expect it to take more passes, and expect the middle to want to go chalky if you overwork it.

Same technique, no changes. Cross the new seam at 45 degrees, both directions, light pressure, held at the end of the handle. The cream pulls into the light green and the whole panel runs cream through light green into dark green with no visible steps.

That is the fan brush doing the one job nothing else does as easily. From here the same stroke gives you soft cloud edges, distant treelines and reflections on water.