Why does a coloured wall tint everything near it? Bounce the light and see

Why does a coloured wall tint everything near it?

You paint a wall a soft green, and a week later the white sofa beside it looks faintly minty, the pale cushion looks tired, and your face in the mirror looks a bit off. Nothing has stained anything. This is colour bounce: light that hits a painted wall picks up some of its colour and carries it on to whatever it lands on next.

Below, move a white sofa towards the wall, change the wall colour, and change how much of the wall is painted. The sofa is a plain white in every case, so any colour you see on it is borrowed.

What is actually happening

A matt painted wall scatters light in every direction. White light from the window lands on a green wall, the wall soaks up most of the red and blue, and the light that bounces off is greener than what arrived. When that greenish light reaches a white sofa, the sofa reflects it, so it looks slightly green. White things show this most because they reflect nearly everything, including whatever colour you send them.

Three things control how strong it is. Distance: the effect fades quickly as you move away, which is why a sofa tight against the wall changes colour and one across the room barely does. Area: a whole painted wall sends back far more coloured light than a small patch. Strength of colour: a deep, saturated paint tints more than a pale one, and an off-white barely tints at all. Glossy finishes act more like a mirror, so they send coloured light in fewer directions, while matt paint spreads it around the room.

Where it helps and where it hurts

Bounce is not always a problem. A warm terracotta or pink wall can make skin tones, wood and cream fabrics look warmer and kinder, and that is part of why those colours feel cosy. A soft sage can calm a bedroom.

It hurts when you want a colour to stay true: a pale grey sofa beside a yellow wall can look dirty, a white kitchen wall next to a strong blue one can look cold, and a mirror or dressing table in front of a strong colour will cast it on your face. Dark, saturated colours in a small room are the biggest culprits, because everything is close to the wall.

How to check before you paint

• Use a big sample. Paint or stick up a sample at least A3 size (about 30 × 42 cm). A tiny swatch sends back too little colour to show the effect.
• Put the sample where it will matter. Hold it next to the sofa, the bedding or the mirror at its real distance, and look in morning and evening light.
• Check the surroundings. Pale fabrics, white skirting and your own face are the first to show a tint.
• Rentals: a large paper or card sample taped up, or peel-and-stick sample sheets, lets you test without committing to paint.

Free and cheap ways to tame it

You do not need to repaint. Pull the sofa 30 to 60 cm off the wall, or swap in a cushion or throw in a neutral that does not fight the wall. Paint only one wall instead of all four, or choose a slightly paler version of the same colour. Hang a big mirror or a warm-white lamp so the room has more neutral light bouncing around than coloured light. Move a mirror to a wall that is not painted a strong colour if your face looks off in it.

Break the rule when you love the effect: a dusky pink wall that flatters a cream sofa is bounce working for you. The point is to choose it on purpose, not to find it afterwards.