Emulsion, for walls and ceilings
Emulsion is water-based, dries in a few hours, has little smell, and washes out of brushes with water. It is sold in three main finishes:
- Matt has no shine and hides uneven plaster best. Ordinary matt marks easily; versions sold as durable or washable are made for halls, stairs and children's rooms.
- Silk has a noticeable sheen and wipes clean, and shows every dent and ripple in the wall behind it.
- Soft sheen lies between the two.
Emulsions labelled for kitchens and bathrooms are formulated to resist moisture and mould. Ceiling paint is a matt emulsion made to spatter less from a roller.
Gloss, satin and eggshell, for wood and metal
Doors, skirting boards, window frames and radiators take more wear than walls and are painted with a harder finish. Gloss is the shiniest and most hard-wearing; satin, often sold as satinwood, has a medium sheen; eggshell is nearly matt.
Each is made in two forms:
- Water-based finishes dry within hours, have little smell and stay white. They show brush marks more readily and take some weeks to reach full hardness.
- Solvent-based finishes, the traditional oil paints, flow out to a smoother surface and are tougher at first. They smell strongly, take up to a day between coats, need white spirit to clean brushes, and white versions yellow with age, fastest where daylight is poor.
Primers and undercoats
A primer seals a bare surface and gives the next coat something to grip. An undercoat builds an even, opaque base of the right colour beneath the finish. Many products combine the two.
- Bare wood needs a wood primer, with knotting solution applied first to resinous knots, which otherwise bleed through as brown stains.
- New plaster is sealed with a mist coat: matt emulsion thinned with water as the tin directs, applied once the plaster has dried to an even pale colour. Vinyl silk is not used for this, because it forms a skin that can peel.
- Bare metal needs a metal primer, and rust has to be removed or treated first.
- Stains from water, smoke or nicotine come back through emulsion however many coats are applied. A stain-blocking primer seals them, once the cause of any damp has been dealt with.
- A strong colour being covered by a pale one is hidden more economically by an undercoat than by extra coats of the finish.
Masonry paint
Rendered, pebble-dashed and painted brick walls outdoors are painted with masonry paint, sold smooth or textured. Walls of older solid construction need a finish that lets moisture escape, such as limewash; the reasons are set out under painting the outside of a house and limewash walls.
How much to buy
Every tin states its coverage in square metres per litre. For emulsion on a smooth, sealed wall this is commonly between 10 and 13. The area of each wall is its height multiplied by its width, less doors and windows; most jobs need two coats, and bare or textured surfaces take more. Buying enough of one batch for the whole room avoids small differences in colour between tins.
The solvent label
The solvents that evaporate as paint dries are volatile organic compounds, or VOCs, which affect indoor air and contribute to air pollution. Legal limits on the VOC content of decorative paints are set by the Volatile Organic Compounds in Paints, Varnishes and Vehicle Refinishing Products Regulations 2012.
Many tins also carry the VOC Globe, a voluntary label run since 2018 by the British Coatings Federation, the industry's trade body. It places the product in one of six bands:
- Trace — below 0.1 per cent
- Minimal — 0.1 to 0.29 per cent
- Low — 0.3 to 7.99 per cent
- Medium — 8 to 24.99 per cent
- High — 25 to 50 per cent
- Very high — more than 50 per cent
Water-based emulsions generally fall in the lowest bands and solvent-based gloss in the higher ones. No paint on general sale is entirely free of VOCs, whatever the wording on the front of the tin.
Old paint already on the wall
Paint sold for household use no longer contains lead, but paint applied before the 1960s may, and textured ceiling coatings applied before 2000 may contain asbestos. Both are safe while intact and hazardous when sanded. What to do about them is set out under lead paint, asbestos and paint disposal.