THERE are three distinct types of distemper, each possessing its own peculiar merits, and a brief knowledge of their differences and characteristics will be of material assistance in selecting the best material for any particular job.
Types of Distemper
Broadly speaking, all distempers consist of dry colours, like whiting (chalk), and various tinting or staining colours, well mixed with glue-size or other fixative and diluted with water. An oil-bound distemper contains, in addition to the foregoing, a fair amount of oil emulsion to give a washable and waterproof finish.
In addition to the glue- or size-bound distemper, and the oil-bound variety just mentioned, there is another popular type known as washable distemper, which (although not as resistant to water as the oil-bound class) is yet capable of withstanding a light sponge down. Any attempt to clean size distemper in this manner would be disastrous, for the whole coating is very easily removed by moisture.
When and when not to use. This problem must be faced sooner or later, and with several products at our disposal it frequently happens that one type of distemper may be a complete success where others would fail. On the other hand, there are materials such as iron, glazed tiles, glass, oil-painted or varnished surfaces, and woodwork, which are quite unsuitable for the reception of distemper of any kind.
Good surfaces are those of an absorbent nature, providing also that they are permanently dry and free from undue movement. A slight roughness of the surface assists adhesion, enables a thicker coating to be applied, and gives a better finish. Such surfaces as plaster, cement stucco, wall board, plaster board, asbestos, brickwork, stone, and paper, offer the right degree of porosity for all types of distemper and rarely give trouble, but woodwork, owing to its seasonal expansion and contraction, is liable to cause flaking.
Special attention must be given to Portland cement and hard wall plasters of the Keene’s cement type when highly finished by the plasterer. Although fairly porous, these materials present smooth, hard and cold surfaces which encourage condensation. In these circumstances the best distemper is the one which does not permit moisture to penetrate, I.e. the impervious oil-bound type.
Obviously, iron surfaces would rust and discolour any form of water surfaces before excessive moisture has had time to dry out. The period necessary will vary according to conditions, making it difficult to lay down hard and fast rules; but it is suggested that the following will serve as a guide:
Repair work, approximately 1 in. in thickness and extending down to the old brick or stonework, a fortnight.
New work (hollow- backed), such as lath and plaster ceilings and walls, or partition walls or breeze blocks, a fortnight.
New brickwork or concrete, if plastered in spring or summer, two to three-months; if in late autumn, six months.
Old wallpaper will prove unsuitable when printed in dark, contrasting colours, when damaged by dampness, or when the paste has become perished and lost its paint, but non-ferrous metals being free from this objection often prove satisfactory when coated with oil-bound distemper. The action of heat or of excessive humidity in the atmosphere are the destructive elements which destroy the fixative and cause premature flaking of any distemper.
Painted or varnished surfaces have two serious drawbacks, first on account of condensation which occurs sooner or later when such materials are coated with either size-bound or washable distemper, and second because old paint or varnish is always sufficiently elastic (especially in hot weather) to expand and crack any harder coating applied over it.
Newly Plastered Work
Time and material will be wasted by any attempt to decorate these adhesive properties. (This latter failing does not apply to odd, loose edges which are easily pasted back.)
What type to purchase, and in what quantity, are the next problems. Choice of colour is a personal matter, but it is wise to select warm tints (yellow, pinks, and colours containing these hues) for sunless rooms facing north and east, keeping the colder blues and greens for rooms of a southern aspect.
Oil-bound distemper is particularly suitable for walls of kitchens and bathrooms, and in situations where slight dampness exists, for here it is less likely to show that marked patchiness exhibited by other distempers. Washable types are useful for living rooms and passages, while ceilings, bedrooms, and spare rooms may be finished in ordinary size distemper.
The amount required is calculated on the basis that each pound of distemper purchased will cover (when thinned with water) six square yards of surface, one coat only. The average ceiling of 5 by 4i yards will therefore require 41b., but it is always wise to mix a little too much in case the surface is exceptionally absorbent. Whether bought in paste or powder form, containers of 4, 7, 14, 28, and 561b. Are usually available, the larger amounts being more economical.
Powder distemper is added slowly and well stirred into its own weight of water to render it ready for use.
Paste distemper mixes more easily if warmed for a few minutes over a gas ring; cold water is then added a little at a time, any lumps being stirred and ground out against the side of the pail. When quite smooth, dilute to a brushing consistency.
Home-made distemper is cheaply and easily prepared, and although not so finely ground as the ready made types, is perfectly reliable. Any decorators’ merchant sells the materials, which are mixed as follows: (I) Place 3lb. Of ordinary whiting in a clean pail, pour on -gallon of cold water and leave to soak. (2) In another pail mix \b. concentrated size with I-gallon of boiling water. Now pour off all water not absorbed by the whiting and stir until a smooth paste results, adding liquid size as necessary. (3) Any desired colouring must next be prepared by mixing separately (and thoroughly) in a little water. Lime green, lime red, lime blue, yellow ochre, umber, or a vegetable black, may be used (single or intermixed) to tint the whiting to the desired colour. This must be ascertained by trial on a slip of paper which may be dried near a fire in a few seconds. (4) Sieve, in small quantities, through muslin to ensure a smoother mixture. (5) Add liquid size until of brushing consistency.
Correct preparation is important, especially when work is to be finished in oil-bound or washable distemper. Old distemper must be completely removed by washing, scraping and sponging with water until no trace remains. Obviously, an oil-bound distemper cannot be removed, but washing with sugar soap is advisable to remove dirt, grease and any parts on the point of flaking.
Defective plaster . Minor cracks and holes should be filled with a mixture of plaster of Paris and distemper.
Bad stains on ceilings must be prevented from discolouring the new work. A preliminary coating of the part with either flat paint or distemper. Washable, or size distemper should be applied over a first coat of weak jellied size mixed with a quarter of its bulk of the finishing colour.
Distemper dries quickly, and therefore must be applied rapidly and with a wide brush. Close doors and windows until the job is finished, and distemper the walls.
When applying distemper always coat each strip of surface before the edge of the previous one is dry. Apply a liberal coat with brush strokes worked vertically, but do not miss even the smallest part, for touching up afterwards will show prominently.
The completion of each wall provides an ideal opportunity for oil-bound distemper is usually effective.
Painted or varnished surfaces. The best preparation is to hang with lining paper to minimize condensation.
Asbestos sheets. All nail heads should be painted to prevent rusting; then fill and level all joints and hollows with stopping.
Definite rules are laid down as to the proper undercoat for each type of finish employed, the object being to eliminate uneven porosity of the surface. Oil-bound distemper is usually mixed with an equal quantity of petrifying liquid (obtainable from decorators’ merchants) and water, or with water only if the surface was previously finished in this type of the removal of any splashes from paintwork or floor. If tackled immediately with a clean damp cloth, much hard work will be avoided and the job left in a workmanlike manner.
Neat stencil and stipple line borders may be applied to the wall in contrasting colour, by a stencil plate cut. Use a good stencil brush and do not overload with colour. Mark off the base lines in pencil as a guide before applying stencil pattern to wall. A simple method of stippling a border to a wall or similar surface is by the use of a plain mask and stencil brush.