How to Use Acrylic Retarder to Slow Drying Time

Greg uses two products from the same acrylic brand: a slow-dry matte liquid and an acrylic retarder. Each one works alone, and he suggests trying them separately first to see how you like them. He found that mixing the two gave him the best balance of long blending time and a sensible drying time. Any brand's retarder and slow-dry medium can be used the same way.

Pour equal parts retarder and slow-dry medium into a clean squeeze bottle, cap it and shake it to combine. Then label it. Greg writes "take it slow" on his. A plain white bottle of medium looks the same as a bottle of white paint, and grabbing the wrong one mid-painting would undo your work.

One way to use the mix is to coat the area you plan to blend before you add paint. Greg squeezes a line of medium across the top of a canvas he has already painted dark blue-grey. Use only what you need for the section you can work in one go. The medium keeps that area open while you blend.

Spread the medium into a thin, even coat with a foam brush, working top to bottom. Add a little more where it looks dry so the whole area is covered. Greg prefers cheap foam brushes from the hardware store because they are less porous and don't soak up as much medium. Keep the coat thin. Puddles will stay wet far too long.

Mix a little of the medium into your paint on the palette as well. Then lay down your first light strokes. Greg blocks in rough cloud shapes in pale grey, pink and white straight into the wet coat. Don't worry about the shapes yet. The point is to get paint down while the surface is open so it can be blended.

Take a completely dry brush and softly push the paint around. Greg calls this badgering: light, quick touches that melt one value into the next. It may look like he presses hard, but he barely touches the surface. A damp brush would lift the paint instead, so keep a dry one ready.

Keep working the edges, adding light and dark as needed. Use a separate dry brush for each value: one for the brightest highlights, one for white and one for mid-tones. That stops you dragging one color into another. It takes practice to learn which corner and angle of the brush to use without disturbing what you have already blended.

After about 10 to 12 minutes of blending, Greg's sky still has a wet shimmer and the paint still moves. Without the medium, the same paint would have dried within minutes. When you are happy, stop and let it dry. The 50/50 mix sets up once you leave it alone, so you can paint the next layer the same day.