STANDARD PAINT FOR HOUSES

Wanganui Chronicle, 1 December 1949, Page 7

STANDARD PAINT FOR HOUSES

A new specification for ready-mixed paints to be used for painting outside woodwork, issued last year by the New Zealand Standards Institute, promises to check the frequent repaintings that have been found to be necessary on many houses in New Zealand. Under normal conditions a house should not need repainting under 7£ years, and on this basis the Paint Section of the Dominion Laboratory, Department of Scientific and Industrial Research, has collected considerable data on thousands of houses in New Zealand. Before the last war, paint specifications for exterior woodwork varied, and during the war, through shortage of materials used in the manufacture of paint, an emergency specification was accepted that covered a lower grade of paint.

The Paint Section gave assistance in the preparation of the new specification, and is responsible for the analytical check-tests of these paints. There is no upper limit of quality, but the specification lays down a minimum grade of the various paints suitable for undercoats and finishing coats; it is the minimum grade of the best quality acceptable to the painting trade below which the paint manufacturer must not go if he wishes to sell the paint under the Standard Mark or under certification of conformity with the specification. The Specification, the full name of which is “New Zealand Standard Specification 521 for Ready Mixed Paint for undercoats and finishing coats for exterior use on woodwork (white and light tints),” is necessarily a rather long and technical document. The composition, quality and requirements of each of the raw materials, and the manufacturing procedure, are given in detail, but even more stress is made on the performance of the paint. Drying and brushing properties, spreading rate, and hiding power are defined, and recommended thinners and driers are given. The application of the paints is also referred to, particularly in relation to the appearance and drying of completed work. Letter symbols are used for marking the paint containers to show the type of paint. These symbols and their order bear relation to the materials used; for instance, “type L.A.Z.T.” would mean that the pigment consisted of genuine white lead (L), antimony oxide (A), zinc oxide (Z), and titanium oxide (T), the proportions being in this order with the largest first; if other pigments are added they must be given a letter symbol if they constitute more than five per cent, of the total pigment. Improved methods of analysis of paint pigments at the Dominion Laboratory has helped in the checking of Standard paints; for field tests the laboratory have installed, in widely separated parts of the country, test fences comprising in all about 1000 panels. From periodical visits chemists of the laboratory obtain important data on the many qualities of paints when exposed to all weather conditions, and since all but a few of the paints used were made in the laboratory, this work will be of considerable assistance in advising on specifications.