The type of paint you select depends on both the finish you want and the material you are decorating. Various additives adapt the qualities of paint for different uses.
Emulsion paint is the most popular and practical finish for walls and ceilings. It has a binder made from synthetic resins, which are dispersed in a solution of water. Exterior-grade emulsions, specially formulated to be weatherproof, are also available.
Solvent-based (oil) paints are a mix of oils and resins. Paints made from natural resins are very slow to dry so most modern paints contain synthetic versions to make them fast drying.
During manufacture, along with the pigments that give the wide range of colours, certain additives are included to give paint qualities such as high gloss, or non-drip.
Thixotropic paints are sold as non-drip paints. These are almost jelly-like in the tins, letting you load the brush quicker without drips. In other instances, manufacturers add extenders to fill and strengthen the paint. Cheap, budget paint contains lots of filler. While you get more paint for your money, it often means the paint doesn’t cover as well and so you need extra coats. Reinforced emulsion has powdered mica or similar fine aggregate added to it to make a water-thinnable exterior grade emulsion paint that dries with a textured finish.
Paint that is too thick cannot be properly applied and needs to be thinned down before use. Some finishes require special thinners supplied by manufacturers, but most domestic solvent-based (oil) paints can be thinned with white spirit, while emulsions can be thinned with water. Turpentine will thin oil paints but it costs more than white spirit.
The proportion of pigment to resin affects the way in which paint sets. A shiny, gloss paint has approximately equal amounts of resin and pigment. A higher proportion of pigment produces a matt (dull) paint. By adjusting the proportions, it makes it possible to produce eggshell or satin finishes. Matt paints cover well because of their high pigment content, while the resins in gloss paints give them their strength.
Solvent-based (oil) paints are suitable for painting metal. There is a wide range of specialized finishes available: metallic finishes (which contain aluminium, copper, bronze or even gold powders); non-setting security paints used for rainwater and down pipes (the paint remains slippery to prevent intruders scaling walls via external pipes); non-slip paints (ideal for metal spiral staircases and external fire escapes); and radiator enamels (a heat stoving acrylic paint, which can also be used to repaint central heating boiler cabinets, refrigerators, washing machines, and cookers).
Preparing Paint For Use
Whether you are using freshly purchased tins of paint, or making use of some ‘left-overs’ from a previous job, always remember to wipe the paint can to remove dust and dirt. Then prise the lid off with the side of an old, sturdy knife blade. Don’t use a screwdriver, as this could make the lid buckle up and stop it from forming an airtight seal so it will be difficult to open next time.
Gently stir liquid paints with a clean, broad wooden stick to blend the pigment with the medium. There’s no need to stir thixotropic paints but if the medium has separated, stir it and leave it to gel again before use.
Where a skin has formed on paint, cut around the edge with a knife and lift the skin out in one piece with a clean stick. Next time you put away a tin of paint, store it upside down. Then if a skin does form, it will be at the bottom of the tin.
Old paint needs to be strained through a nylon stocking or a piece of muslin into the paint kettle, so that any loose bristles, flakes of dust and dirt or bits of paint skin are removed.
Before you dip a brush into your paint, you’ll need to prepare it to make sure it’s clean and not shedding any hairs or fibres. Even new brushes will shed hairs so it’s a good idea to rub the bristles in the palm of your hand to dislodge dust and loose bristles. Professional decorators never use a new brush for finishing paint-work. Instead they always ‘run in’ new brushes by painting on primers and undercoats.
Prepare new rollers by soaking them in warm, soapy water for a few hours before use. This will release any loose fibres that might spoil the finish. Rinse in clean water and dry the roller thoroughly before use.