Exterior Decorating: Treatment of Special Surfaces
Unpainted outside garden woodwork should be coated with creosote or with a branded wood preservative to protect it against weather. It is best to apply the preservative with an old brush which once having been used for this purpose, should never again be used for applying paint. Outside creosoted surfaces that are to be resurfaced with paint must first be sealed or the preservative will burn through the new coats of paint.
The sealing of these surfaces may be done by applying a coat of shellac knotting or coating the work with aluminium priming paint. New cement surfaces should not be painted with oil paints until they have weathered sufficiently to kill their alkali content, but new cement surfaces may be coated with cement paints specially manufactured for the purpose — these colouring finishes contain a good percentage of cement powder, and they should be applied with a wide brush. Outside cement surfaces and brickwork may be coated with emulsion paint or distemper.
If new galvanized iron is coated with oil paint the new decoration will have a short life, as the galvanized finish of the iron contains chemicals which react to oil paints. The iron should either be allowed to weather, for at least six months, or if it is necessary to coat it as soon as it is fixed in position, the galvanized iron may be artificially weathered by the application of a solution of 2 oz. Of chloride to a quart of water. The chloride should be applied liberally to the metal sheeting and left for 48 hours before rinsing it thoroughly. Metalwork must be allowed to dry before being painted. Weathered, or artificially weathered, galvanized iron may be coated with oil paint but the best type of finishing materials for these and other metal surfaces are metallic paints which have anti-rusting properties.
All the work of outside decorating should be done with the same care that is applied to inside surfaces. It should always be remembered that exterior decorating performs the double function of protecting the surfaces and brightening with gleaming new colours.