Opaque Paint Outdoors: Kit, Palette, Drying

Opaque paint works differently from watercolour. You don't use the white of the paper as light — you lay every highlight down yourself, with paint that swallows what's underneath. That means you can paint light over dark, cover mistakes and work on toned board. For that you need to know how quickly your paint dries and how to keep it workable outdoors. That's exactly what this lesson is about.

Gouache and acrylic compared

Gouache can be re-wetted after it dries. Run a damp brush over an old layer and you wake it up, letting you smudge or lift it. That's both an advantage and a trap: correcting is effortless, but if you go over a finished area too wet, you stir it up and the colours turn to mud. Gouache dries matt and velvety, with no sheen, and looks calm and unified in a sketchbook — which makes it the more obvious medium when you're working in a book. Expect a shift in tone as it dries: dark, saturated mixes usually dry a touch lighter, while tints with lots of white sometimes look darker than they did wet. So never judge a mix while it's wet — try it on a strip at the edge and wait twenty seconds.

Acrylic goes the other way: once dry, it's waterproof and stays put. You can lay down as many layers as you like without disturbing the one below. The price is speed. Outdoors, acrylic dries in minutes, and even faster in sun and wind — not just on the paper, but on your palette too. So bring a small spray bottle of water and mist your blobs of paint every few minutes. Even more convenient is a stay-wet palette: a shallow container with a sheet of damp kitchen paper in it and a piece of baking parchment on top, with the paint on that. This keeps acrylic workable for half an hour or more. And one rule is absolute: never put down an acrylic brush without standing it in water. Dried acrylic in the ferrule will never come out.

Five tubes are enough

Your travel kit consists of titanium white, a primary yellow, a red in a cadmium or pyrrole red tone, ultramarine and burnt sienna. Titanium white can be the biggest tube, because it runs out fastest: with opaque paint, white goes into almost every mix. With ultramarine and burnt sienna you have the whole range from warm browns through neutral greys to deep, almost black tones — that's what you paint roofs, asphalt, shadows and window openings with. Ultramarine and yellow give you green; red and yellow give you the orange of brick and awnings. Optionally add Payne's grey, a convenient, slightly bluish dark for shadow areas and evening subjects. More tubes won't give you better pictures outdoors, only longer decisions.

Brushes, water, rag

Take two flat brushes, roughly size 6 and 12, and a small round in size 2 to 4. The wide flat lays in walls, sky and streets in a few strokes; with its narrow edge you can pull clean edges at the same time, without switching tools. The small round is for glazing bars, aerials, lampposts and suggested figures. Add a water pot with a lid — a screw-top jar or a collapsible cup — so the water doesn't spill in your bag. The rag matters more with opaque paint than with watercolour: between two colours you usually just wipe the brush out rather than washing it, because too much water destroys your covering power.

Surface and pans

Opaque paint takes moisture and several layers, so you want paper from 250 gsm upwards. It's especially lovely on toned board in grey or ochre: the midtone comes free, you only paint the lights and the darks, and every white stroke instantly reads as sunlight. Small painting boards in A6 or A5 are the third option — stiff enough to sit on your knee without a table.

If tubes feel too fiddly out and about, use gouache in pans. Travel sets like these, at around CHF 30 to 60, work like a watercolour box, except that you can mix the paint opaquely and the lid serves as a palette. The key is to pick up plenty of paint with very little water, otherwise it ends up as nothing but a thin glaze.

Key points

Gouache forgives, acrylic forgets nothing — choose according to whether you want to correct or to layer. With opaque paint, white is a consumable, while water is something to ration. And judge every mix only once it's dry.

Exercise

Stand with your kit at a window or on a balcony with a view of a building and give yourself 15 minutes. The first seven minutes belong to a colour chart on a scrap sheet: using only ultramarine and burnt sienna, mix a row of five swatches, from pure blue through two neutral mixes to pure brown. Underneath, lay down the same five mixes again, each lightened with a dab of titanium white. That gives you ten tones that will carry almost any urban subject. In the remaining eight minutes, find a house wall and paint it opaquely with the size 12 flat alone, in three values: the sunlit plane light, the turned-away plane mid, window and door openings dark. No lines, no details, just three flat tones — and when you apply them, use so much paint and so little water that the surface doesn't show through.