EXTERIOR FINISHING OF COTTAGES. '263 537. T/ie colouring of outside walls is most commonly effected by water colours, when the surface of the wall is new ; or by colours incorporated with glutinous substances or oils, after the walls have been thoroughly dried. As a general rule in colouring walls, it may be laid down, that colours unmixed with glutinous bodies, and held in solution by water alone, may be laid on the wall at any time when the temperature is ten or twelve degrees above the freezing point, and in no immediate danger of falling lower, whether the walls are wet or dry, new or old. Colours mixed with glutinous matters or oils, on the other hand, should not be laid on new walls till they are thoroughly dried ; or on old walls at a season of the year wlien their surface may be saturated with mois- ture. The reason for these rules Ls, that water colours do not impede the evaporation of moisture from the wall, and the absorption by the mortar of carbonic acid gas, by which it is hardened and rendered durable ; while glutinous colours, by closing up the pores of the surface, do both. 538. IFater colours for outside walls are generally formed on a basis of quicklime, Roman cement, tarras, or Puzzolano. With one or other of these the colours are mixed as wanted, and are immediately laid on with a whitewashing brush. By far the most favourable time to do this is when the wall is newly built, or the plaster is recently laid on. In the case of old walls, they must first be thoroughly scraped, washed, and stopped ; and afterwards brushed over with the colouring mixture, either as a flat shade, or clouded, as the expression is, to imitate the effects of time. This last purpose will be materially aided by taking any strong acid that combines with lime, or any metallic oxide, that will, of course, absorb oxygen from the atmosphere, and mixing these with water, in two separate pails, occasionally dipping the brush in one or the other. A very convenient acid is the sulphuric, in the proportion of one to ten of water ; and a suitable oxide is the sulphate of iron, dissolved in water, in about the same proportion. The blotches moistened with the sulphuric acid will in time assume a rich cream colour, and those touched by the copperas will have a reddish tinge. 539. Glutinous colours for outside walls also take for their basis quicklime or some cement ; and the glutinous matter is either blood, kept stirring till cold, to prevent it from becoming clotted, stale milk, or vegetable oils. Size and paste are sometimes used as glutinous media ; and, in such cases, alum is mixed with them, to prevent tliem from fermenting, and becoming mouldy on the walls ; but they are not durable, and, if exposed to driving rains, soon wash off. The desired colours are added to the glutinous matter, which is laid on of such a consistence as to part easily from a common whitewasher's brush. 540. Painting the outsides of walls in oil colours is too expensive for cottages, and, on the whole, is unsuitable for any structure not formed of timber. As a medium of giving colour, it is more expensive, and not much more efficient, than glutinous colours formed with blood ; and, as a protection from the weather, three coats of oil paint are nearly as expensive, and far less effective, than one coat of quicklime and sharp sand, which will last as long as the atmosphere contains oxygen, and will grow harder as it grows older. In the United States of America, however, the exteriors of brick houses are said to be frequently " painted in oil, the colours being most commonly red or brown." It is also said that " the Dutch very generally cover their buildings with a composition of mortar, or plaster, mixed with oil and colour : blue, red or light pink, and grey, are the most common tints. These walls, when dry, have a kind of gloss like varnish, and of course resist wet." (Meek. Mag., vol. iv. p. 98.) It appears to us that the protection afforded by this oil-colouring is not sufficient to atone for the bad taste which it displays. 541. The kinds of colours most suitable for exterior walls should generally be such as belong to the stones or bricks of the country in which the dwelling stands. These are chiefly whites, browns, yellows, reds, and greys. Yellow, red, and brown ochres are among the cheapest of colours ; and fi-om these, with whiting, chai-coal, and bistre (or soot, fi-om which bistre is made), all the colouring desirable for the outsides of cottages may be produced. 542. Splasking is a mode of colouring walls, which may be performed with equal success, as far as immediate effect is concerned, in water, in glutinous, or in oil, colours ; and, in regard to the state of the walls, the same rules will apply in this case that have been already laid down in § 537. The object of splashing is either to imitate the lichens and weather stains of an old wall, or some particular kind of stone. It is seldom attempted in water colours, from their transient duration in the open air, but answers perfectly well with colours mixed with either blood, milk, or oil. The surface of the wall to be splashed must be well seasoned, and perfectly dry ; and should reseinble, as much as possible, the form of the stone or wall to be imitated ; and the prevailing or groundwork colour of that wall should be given to it, by one coat over the whole. Then, several pots of different colours being mixed up, and a long painter's brush, called a duster, being put in each, the artist, holding a short stick in one hand, takes in the
