Dark colours, LRV and the extra coats they cost

Why dark colours cover badly

A can of paint hides what is under it mainly through its white pigment, titanium dioxide, which scatters light very effectively. Pale colours are made by adding a little colourant to a white or pastel base that is full of it. Darker colours need more colourant, and colourant takes up room in the can, so they are mixed in bases with progressively less white: a medium base, a deep base, and for the strongest colours an ultra-deep or clear base with almost none.

The result is that a deep colour spreads just as far per gallon as a pale one, but hides much less per coat. Over a white wall, two coats of navy or forest green can still look patchy, with the white showing faintly where the roller ran thin and at the cut-in edges. Saturated reds, oranges and yellows are worse, because the pigments that give those colours their intensity are themselves fairly transparent.

LRV: the number that warns you

Light reflectance value (LRV) measures how much visible light a colour reflects, on a scale from about 0 for the deepest black to about 100 for the brightest white. Most US paint makers print it on the back of the chip, in the fan deck, or on the colour’s web page. It is the most useful single number for planning coats, because it tells you how far apart two colours are in lightness, whatever their hue.

The LRV bands are a working scale for estimating, not an industry standard, and brands differ. What matters is the size of the jump: going two steps or more down this table, or two steps up, is where two coats stop being reliable. The coats calculator uses these five steps.

Primer or a third coat

There are two ways to get a deep colour to hide a light wall. One is a third coat of the finish paint. The other is one coat of primer tinted toward the new colour under two finish coats; for the deepest colours and for saturated reds and yellows, the tint is usually a grey, which gives the most even base. Primer costs less per gallon than most finish paints and is often the more even result.

The same logic runs the other way. Going from a dark wall to a light colour, the old colour ghosts through; a high-hide primer, white or tinted toward the new colour, stops it in one coat.

Accent walls: where it bites

A single dark wall is the most common place to run short, because the quantity is small enough that a gallon looks generous.

Test before you commit

Dark colours shift more with light than pale ones. A navy that looks crisp on a chip under store lighting can read nearly black on a north-facing wall in the evening. A sample pot, 8 fl oz, covers about 10 sq ft at two coats, enough for a 2 × 2 ft patch that you can see in morning and evening light. Paint two patches side by side if you are choosing between shades, and paint them on the actual wall, or on a white board you can move, rather than judging a chip held against the old colour. The sample pot calculator counts pots and cost.

Rolling a dark colour

Technique matters more with deep colours, because every thin patch and every lap shows. Load the roller fully and keep it loaded; a roller running dry leaves a lighter streak that the next coat may not hide. Use a good-quality cover with the nap the can recommends, often 3/8 in on smooth walls, and roll a whole wall from corner to corner without stopping, keeping a wet edge. Cut in two or three feet ahead of the roller, not the whole room first, so the brushed edges are still wet when the roller meets them; dry cut-in edges in a dark colour show as a frame round the wall. Finish each wall with light, full-height strokes in one direction.

Sheen and dark colours

Dark colours show surface flaws and roller texture more than pale ones, because the contrast between light and shadow is stronger. A flat or matte finish hides the most. Dark colours in higher sheens also show “burnishing”, shiny patches where furniture rubs or hands touch. The paint sheen comparison gives the usual sheen for each room; for a dark accent wall, one step lower than the room’s usual sheen is common.

Touch-ups and leftovers

Dark colours are the hardest to touch up invisibly. Touch-ups flash, showing as a different sheen, if the paint has thickened in the can or is applied with a different tool. Keep a quart of the exact batch sealed, write the colour code and the sheen on the lid, and touch up with the same kind of roller or brush used for the wall. The leftover and touch-up planner works out how much is worth keeping.

Outside: heat and dark colours

On exteriors, LRV matters for another reason. Dark colours absorb more of the sun’s heat, and some siding materials, vinyl in particular, can warp if painted a colour darker than the manufacturer allows. Several paint brands sell ranges of colours formulated or approved for vinyl. Check the siding maker’s guidance before painting vinyl a dark colour.

Common mistakes

• Buying a gallon for a dark wall. Three coats of 112 sq ft is 336 sq ft, leaving no allowance at all.
• Using untinted white primer under a deep colour. Tint it, or use grey.
• Judging the colour from the chip. Paint a patch on the wall and look at it at night.
• Expecting a “one-coat” paint to cover a big jump. It may on a similar colour; it rarely does from white to navy.
• Rolling dark colours thin to stretch them. Thin coats in dark colours show every lap.
• Touching up months later from a thickened can. Stir well, and touch up whole sections to the corners if it flashes.

For two colours on one wall, see two-tone and wainscot walls; for when primer is needed whatever the colour, primer: when you need it.