THIS article is mainly concerned with interior oil painting, and a brief description, at the outset, of the nature and uses of the three main types of oil paint will enable the reader to select and use these materials with greater confidence. Each type contains four ingredients, which are: (I) the pigment or colouring matter (which may, of course, be white), (2) a drying oil such as linseed oil, which binds or fixes the pigment by the formation of a slightly elastic film which makes it glossy, tough, washable, and resistant to variations in weather conditions, (3) a drier, which accelerates evaporation and enables the paint to dry in eight hours instead of as many days, (4) a thinner, such as turpentine or a reliable brand of white spirit, which, by thinning the paint makes it easily brushable, and dry quicker and harder, but which considerably reduces its gloss.
By varying the proportions of oil and turpentine, it is possible to produce any of three main types of paint, or, if necessary, change the character of ready-mixed paint. Glossy paint contains five or six parts of oil (or varnish), to one of turpentine. Flat oil paints contain approximately one part of oil to six of turpentine. Semi-gloss paints (employed as undercoats) contain equal parts of oil and turpentine. For house painting it is safe to assume that glossy paints (particularly those containing white lead) will give reliable service upon outdoor work, and upon those positions indoors where frequent washing down is necessary. Flat oil paints are used for interior work only, and are employed mainly upon ceilings and walls, where their matt surface is often mistaken for oil-bound distemper. The similarity is limited to appearance only, however, for in practice a flat paint will be found to withstand considerably more washing down and is so much more stable than distemper that after thirty or forty years of accumulated coatings there is rarely any sign of chipping or peeling off.
When purchasing paint it is advisable to purchase ‘decorator’s quality’ from your local builders’ merchant. Not only does he carry a wide range of paints but he will be able to give sound advice as to their suitability for any particular purpose. As some paints, particularly those containing a large proportion of zinc oxide (white), are unsuitable for outdoor use, while others are equally good for both exterior and interior work, it is wise to state your requirements clearly. Titanium oxide paints for both interior and exterior use are to be recommended, as they possess remarkable covering power and, unlike lead oxide paints, are nontoxic (I.e. safer to handle).
This involves (1) the production of a smooth, dry surface, quite free from dust, grease, dirt, old wallpaper, or distemper, (2) special treatment for certain types of surface which are normally unsuitable for the reception of oil paint, (3) the application of a first or priming coat of paint (never glue size) when points (1) and (2) have received attention. This priming should contain enough linseed oil to correct porosity in the surface, and should be sufficiently thin to penetrate well into the material being painted, thus ensuring perfect adhesion.
Previously Decorated Surfaces
These embrace six main classes, and their treatment should also indicate a line of procedure for others not included. (A) The most easily prepared work is that previously finished in flat or semi-gloss paint. Here, a scrub down with hot water and sugar soap (or washing soda), followed by rinsing with clean water, is the only treatment necessary. Any roughness of surface can be rectified by rubbing with pumice-stone while the surface is still wet. (B) Glossy paint or varnish needs the same treatment, but will require more rubbing with pumice to produce a dull or matt surface, which will improve the adhesion of the new paint. (C) Blistered, cracked, or other work which is overloaded with paint would take many hours to rub down, but it should certainly be removed. The complete removal of the paint is a much easier and quicker job. Burning off with either a blowlamp or large bunsen burner is generally more satisfactory than the use of fluid, paint remover. (D) Distempered surfaces must be washed with hot water to remove as much as possible of the material. Soap will not be necessary except where grease is present, as for example, in kitchens. (E) Wallpapers require to be stripped off in accordance with instructions detailed in the section referring to PAPER AND PAPERHANGING. (F) Materials requiring special treatment include creosote, tar, tar or bitumen paint, asbestos sheets, and Portland cement. These are rendered safe for painting by first coating with a special sealing solu- tion obtainable from any builders’ merchants, or if the area is not too large, by coating with aluminium paint or a good shellac varnish.
Burning off a Door
The removal of paint from mouldings requires time and care, so it is better to tackle them before dealing with the larger flat areas. Avoid undue charring of the wood and damage to the numerous sharp edges. It may be necessary to go over the work several times in order to leave a smooth surface free from patches of charred paint. The term ‘burning off’ should not be taken too literally; actually the flame is used to soften the paint film in order that it may be scraped off with the shave hook (a special scraper for the removal of paint) and a chisel knife. Nothing will be gained by the application of too much heat. Not more than about 5 in. of paintwork should be softened at a time, and the flame should then be removed while this is cleaned off. The broad flat areas demand a slightly different method. Here, a broad scraper will easily follow the flame in a slow continuous sweep of two feet or more. It will, of course, be found that continual cleaning of the scraper becomes very necessary, and that the best result is obtained when working in the same direction as the grain of the wood The work is finally smoothed with No. ii glass paper and is then ready for knotting (I.e. treatment of knots in the wood by a special sealing liquid) and priming (painting) of the main surface.
There are certain materials such as glass, the thin sheet metal work of motor car bodies, and stained and varnished woodwork, which are easily damaged by a flame1 and must therefore be stripped by a solvent. Among the numerous types will be found a few which are non-inflammable; the remainder must be kept strictly away from any naked flame. Caustic soda solution, an efficient if somewhat drastic paint remover, is injurious to the skin and should be used with discretion, having regard to the surface to be repainted. All traces of the brush-applied solution should be scraped away from the surface and the whole area should be scrubbed clean and left to dry. Use a fibre brush to apply the solution.
Solvents vary considerably; some are capable of penetrating three or four coats of paint in as many minutes while others require a longer period but usually penetrate more deeply. Whatever the type used, repeated coatings may be necessary (applied with an old paint-brush), as the various layers of paint are scraped off. Finally, wash off all traces of the solvent, using turpentine substitute (white spirit) and clean rags. The surface is then ready for painting.
Preparing the Paint
Decorators’ paint of the standard semi-gloss type, in common with many other undercoat paints, will usually require a little further thinning with linseed oil or turpentine, or both. Oil is added only when the porosity of new wood, plaster, etc. calls for this treatment. Equal parts of oil and turpentine are employed to thin undercoats intended for outdoor work, but for interior use a mixture of 2 parts turpentine to 1 of oil is generally preferable.
The question of how much thinners to add can only be settled by trial. There is, however, some comfort to be gained from the knowledge that while over-thinning may necessitate an extra coat of paint, it is far quicker and easier than trying to smooth out (by glasspapering) the coarse brush- work produced by applying the paint too thickly. Thin coats, and more of them constitute good, sound, practice, and it is therefore advisable to thin out the paint and make repeated tests until it can be applied with the lightest pressure of the brush, leaving no brush-mark. Obtain clean edges
Painting a Door
Reference is made to the order of painting and stopping a door. There is, however, one point to be stressed, and that concerns the application of the paint. Enamels and their undercoats have the capacity of flowing out to a level surface after application, but ordinary paint cannot do this, and must be applied more sparingly until (with the brush almost dry) each section of the work can be crossed and laid off with the lightest possible strokes.
Before painting the door casing and skirting, scrape away any accumulated fluff which is often present in the angle formed by woodwork and floor. Furthermore, if the walls of a room are to be papered, it is wise to paint about lin. Of the wall adjoining any woodwork, otherwise it means working to a clean edge at the point where the two meet.
Cupboards may prove awkward unless tackled in the right way, I.e. by painting the inside parts first, then the shelves (working from the top downwards but leaving the top sides unpainted), then the door casing and door edges, thus leaving the doors until the last.
Walls and ceilings offer no special difficulties if painted in a series of strips as recommended for the application of oil-bound distemper.
Both the outside and inside are subjected to rigorous climatic changes, therefore good white lead undercoats are recommended. The brushes required are a1 ½ in. flat, and a part-worn 1 in. or ¾ in. flat brush. The latter is particularly handy when painting to a straight line against the glass.
The procedure followed is to coat all rebates and edges of hinged or swivel type frames which open outwards, with the colour used for the outside, leaving edges which open inwards to be done with the inside colour. The window is then closed (not fastened) and the whole painted, working from the top downwards. This order of working will, of course, have to be varied in the case of sash windows but on completion, the window is left slightly open until the paint is dry.
Edges and rebate must be thinly coated to prevent subsequent sticking, while rust spots on metal casements should be well scraped before the first coat of paint is applied. If this is not done thoroughly, rusting will continue and cause the paint to l1 ft. Some difficulty may at first be experienced when painting upon the putty or other parts in intermediate contact with the glass. It will be found that several long strokes (with the brush only lightly charged with paint) will be necessary to produce a nice straight edge, and if this extends for 1 ½-in. Upon the glass, so much the better. The paint will then fill in any fine cracks between putty and window pane. Any cracks between window frame and adjoining brick or stonework should be filled in with paint, putty, or if very wide, with cement mortar. It is good practice to lash a stout board to the top of the ladder when painting upper windows is to be undertaken.
As the object is to prevent corrosion, the surface must be absolutely dry at the time of painting. It is of equal importance to remove by means of a wire brush and scraper all scale and rust prior to repainting with lead, graphite, bituminous, aluminium or other anti-corrosive paint. Use paper or an old sack to protect garden walls from paint spots.
Gutters and Rainwater Pipes
Obviously, it is equally desirable to paint inside as well as outside the gutters. This necessitates cleaning out any accumulated leaves, dust, etc. and sweeping with an old brush in order to get the inside properly dry. A hook made from stout wire enables a small bucket to be suspended from either the pipe or from a rung of the ladder, leaving both hands free for the work involved. The finest asset is an extension ladder which brings the work within easy reach, and enables one to see clearly and to paint with a small brush those awkward places behind gutters and fall pipes. Other articles of equipment include wedges, for packing the ladder foot where the ground is uneven , two stout boards or short planks for placing under the ladder, when working over soft uneven ground, and a length of thin rope to secure the ladder head to a wall pipe (or other fixture when roof work is involved). In addition, it is a great help to have someone at the foot of the ladder who will hold the ladder firmly so as to prevent any possibility of slipping. A duck board will assist the handyman in gaining access to any roof fittings in need of painting. To paint the exterior of a greenhouse, stout L-shaped angle brackets should be secured at regular intervals at each end of the sloping roof so as to permit the laying on of strong boards to protect the glass and give access to the higher parts of the roof. It will then be possible to carry- out the painting safely.