Coverage of Household Paints
Household paints can be divided into two main types – emulsion-based and oil-based paints. The latter includes those which are polyurethane based. Emulsion-based paint or PEP (plastic emulsion paint) is used now in place of water paint and distemper. Particles of synthetic resin, acrylic or vinyl are suspended in water. As the water evaporates, the particles flow together to form a film of resin on the surface.
Emulsion paint can be used in areas of hard wear, for these can be washed or even scrubbed. Some emulsion paints are used as primers and undercoats. Emulsion paint dries fairly quickly; depending on temperature, you can repaint within an hour or two. The characteristic smell of paint is reduced to a faint odour which disappears quickly. Many people find emulsion paint easy to use, particularly over a large area. It is thinned with water and any splashes can be wiped up with a damp cloth.
For use indoors where you require a quick drying, low-sheen decorative cover, emulsion is suitable for both walls and ceilings. Some emulsions are suitable for both inside or outside use.
The number of coats of paint needed varies on the surface to be covered. Generally, more coats will be needed going from a dark to a light colour than the other way. On new plaster at least two coats will be needed. A thinned coat, diluted with water, should be applied as a sealant before painting with two coats. If you brush out too thoroughly it will not cover too well and an extra coat may be needed.
On a good surface where colours approximate, only one coat may be needed. Cracks should be filled and rubbed down before repainting. A thinned coat of the new colour should be applied to the repaired area before the final decorative coat is applied.
Porous paint should be used for early decoration on new plaster. The wall ideally should be completely dry. This will normally take several months. As it is not practical to leave undecorated plaster for this length of time, you should use a porous paint that will let the wall continue to dry out. They can be used as soon as efflorescence (a crystalline deposit white and fluffy, sometimes hard, especially on cement-based materials when it is known as lime bloom) has ceased.
Emulsion paintis of two types; PVC (homopolymer or co-polymer) or acrylic. These paints decrease in porosity as the sheen increases. They are hard wearing and can be cleaned easily and allow efflorescent salts to pass through.
Vinyl distemper (water paint)is an in-expensive form of emulsion paint. It has a low sheen but is porous. This paint has no great resistance to wear.
Gloss paint or any other that is not porous will prevent the wall plaster from drying out. Trouble may follow if both sides of a newly plastered wall are painted or if one side is tiled and the other painted before the wall has dried out properly. When using porous paint as a temporary decoration, choose one that will suit the permanent decoration. Either use a decoration that can easily be removed or, if planning an oil paint, use emulsion that can be painted over. When repainting, re-paint with paint of the same type as the original used. Some types of paint will not ‘take’ over another paint- for example, a bitumen paint will ‘bleed’ through oil paint.
Oil-based paints all have the characteristic ‘paint’ smell. This includes primers, undercoats, gloss and eggshell finishes. Synthetic resins, alkyd and polyurethane combined with drying oils give a tough flexible finish.
These are slower drying than emulsion paint and need longer drying periods between coats. Thinning is done with white spirit, which is also used forany splashes.
Oil-based paint gives you a wide range of sheen from matt to high gloss. These paints provide hard-wearing surfaces, but the degree of resistance depends on the level of gloss. Oil-based paint is excellent for outside wood and metal work.
Oil-based paint can be obtained in gloss, matt or eggshell finish. Eggshell gives a lower level of gloss. These paints should be used internally in areas of hard wear, such as bathrooms and kitchens. Gloss paint only should be used externally.
It is possible to buy two types of gloss paint; liquid and gell (thixotropic). Liquid gloss needs a little more care in application. Gell is for the less experienced painter. It drips less during application, gives a heavier coat and minimizes the risk of runs and curtaining. Other paints include additives such as silicones and polyethylene.
Distempers – oil-bound and washable
These are used mainly for interior work and will stand light washing. They are not suitable for areas subject to high condensation. Oil-free, size-bound distemper is sometimes used on ceilings. It will not take rubbing and must be washed off before redecorating.
- Exterior Decorating: Painting and Varnishing Woodwork (easydiyinfo.com)
- Decorating Indoors: Painting Woodwork (easydiyinfo.com)
07. June 2012 by admin
Categories: Decorating, Painting | Tags: Emulsion, Gloss (paint), Household Paints, Oil paint, paint, Polyvinyl chloride, Porosity, Synthetic resin | Comments Off on Coverage of Household Paints