Types of Paint for Interior Decorating
Paints are obtainable in a very wide range of colours and shades from localstores and paint shops, and suppliers have colour cards which should be consulted before the job is commenced. Although the improved production of paints has been developed to a great extent in the past few years, there is no universal paint — there are different kinds of paint for different purposes. These may be broadly divided into two main groups: materials for painting exteriors, and materials for painting interiors. There is a difference in the quality of exterior and interior paints; although exterior paints may be used for interior painting, painting materials manufactured specifically for interior purposes should never be used for exterior decorating. For interior work the types of paint may be divided into priming paints, undercoatings and finishing paints; and there are special paints for special materials, such as zinc and asbestos, and galvanized iron, etc.
These paints are used as first coatings. The use of priming paint is not necessary on surfaces that have been previously painted, unless any parts of the surfaces have been rubbed bare, or the paint has been removed with a blowlamp or a paint solvent. There are special priming paints for different types of materials; that used for woodwork is usually termed pink priming and the mixture contains a good proportion of red lead. The priming materials for metal may vary.
Although pink priming paint is the one in most general use for woodwork, and is quite satisfactory for coating new timbers, a recent development in the manufacture of primings has resulted in the production of an aluminium priming paint which is extremely good. Aluminium priming paint is, of course made from the metal from which it derives its name. It is easy to apply and dries with a very good surface to provide a solid foundation for the application of following undercoats and finishing coats. It has only one drawback, and that is it must be frequently stirred when applying it; if this is not done the metallic powder will sink in the medium to the bottom of the container.
Aluminium priming paints also act as sealers and they are especially useful when coating dark woods that have to be finished with a light-coloured paint. A very good feature of aluminium priming paints is that they act as sealers over surfaces previously coated with bituminous compounds, creosote and other wood preservatives. Some manufacturers claim that aluminium paint eliminates the use of knotting but it is generally advisable to seal knots in the usual way before the use of every type of primer.
The main purpose of undercoats is to provide a solid foundation over priming coats before the final work of finishing woodwork and metalwork. Undercoats are very easy to apply, they have plenty of body and they dry with a dull flat finish. Before application of each coat of paint it is necessary to rub down the surface with one of the abrasive materials, usually glass-paper, as described above. The glass-paper has two functions: the main one is to cut down and smooth surface irregularities, also glass-paper provides a criss-cross series of fine scratches which provide a ‘key’ for following coats of paint.
Before the application of each coat of paint, it is necessary to dust the work after rubbing it down. Dusting may be done with a large clean paint-brush or with a ‘duster’ brush. The number of undercoats applied will depend to some extent on the condition of the old surface. In most cases two undercoats will be found sufficient before applying the finishing coat of gloss paint or enamel.
In some cases, where surfaces are in very good condition it may be possible to apply one undercoating only, but this is usually very rare. Some types of finishing paints, particularly the synthetic ones, may also be used as undercoatings, and where this is applicable, manufacturer’s instructions will be found on the containers. Paints used for undercoatings go quite a long way and a pint tin of undercoating should be sufficient to cover a surface of approximately 90 sq. ft., although this may vary between individual manufacturers.
It is advisable, when carrying out interior painting, to use the same family of paints throughout the job and most manufacturers recommend what colour and type of undercoating should be used under their own finishing paints. It is sometimes difficult to estimate the exact amount of paint required, but all types of paints are obtainable in reasonably small quantities.
The amateur decorator should be careful to avoid over-stocking with a particular colour or kind of paint, although a small amount left over is advantageous and may be used later for any retouching which may become necessary. The best way to estimate a job is to make a note of the amount of woodwork to be covered and buy the materials from a good colon/man, or paint shop, where they will advise sensibly on quantities required. In the same way that it is false economy to use cheap tools, it is also bad economically to use cheap paints of any kind, and this applies equally to paints and other materials used in preparatory stages as it does to finishing coats. The difference in cost between good and poor quality paints is very small when related to the covering capacity of these materials, and the saving of a small fraction of a penny on a square foot of paintwork may shorten the life of the job.
Paints for Finishing:
Between different manufacturers there is some apparent confusion in describing finishing paints, but briefly these may be grouped under definite headings such as Hard-gloss Oil Paints or Enamels.
Hard-gloss finishing paints are also known as oil finishing paints because the medium which carries the pigments is linseed oil. Hard gloss paint is suitable for almost every type of interior woodwork and most metal surfaces. They may also be used for painting walls and ceilings of bathrooms, kitchens, etc., and they dry with a good hard-wearing surface and are available in a very wide variety of colours and shades.
Where extra protection is required, as in the case of woodwork in kitchens and bathrooms, it may be advisable to use enamel finishing paints. Enamels have a harder drying surface than gloss paints but they have a shinier surface and may not be considered entirely suitable for painting woodwork and metalwork of sitting-rooms and bedrooms where a more restful finish is required. It will, of course, be appreciated that there are several kinds of hard-gloss finishes and enamels, at least according to manufacturers’ advertisements, and the range of finishes may be extended by the inclusion of synthetic paints which vary from finishing coatings, which may resemble hard-gloss paints, to lacquers, which are really a superior form of enamel paints.
Most lacquers are based on a medium of cellulose and they usually require very fast application to use them successfully. Although the description of the finishing paints is given as ‘glossy’ there are different finishing textures, described variously as `suede’ or ‘eggshell’, etc. Eggshell enamels are really midway between hard-gloss oil paints and enamel finishing paints and as their name implies they dry with a dull, glossy finish, not unlike the sheen of an eggshell. These are particularly useful for woodwork in bedrooms, where a harsh glossy finish is not required.
In addition to the main types of finishing paints described above there is another category of finishing paints. Although manufactured under a variety of trade names they are generally termed ‘Emulsion’ paints. These are ideal for walls and ceilings, but it should be made quite clear that, although they have often been used with apparent success, being water-based paints they do not provide adequate protection to wood and metal surfaces. Steam and damp can penetrate an emulsion paint, and in extreme cases it is possible forto attack the woodwork underneath. Use emulsion paint, by all means, for walls and ceilings, but not for wood or metal.