GLAZING IN STEEL SASHES

Evening Star, Issue 21092, 3 May 1932, Page 2

GLAZING IN STEEL SASHES

PROPER PREPARATION OF POTTY The putty used for glazing in steel sashes caused an English architect considerable trouble, says a report from tho Building Research Station of Great Britain. His specification called for a genuine linseed oil putty, and, although he could neither find fault with tho quality of tho putty used nor with tho workmanship, the putty on some of his recent work had failed to harden and presented a rippled appearance. Ho inquired from the station whether it was possible to suggest tho cause of this trouble, and how to overcome this deficiency in future work. The station replied as follows : —■ “It is known that in certain cases additions are made to putty to prevent hardening, particularly where largo individual panes are glazed, or where considerable temperature movements are to be expected. It is possible that a non-hardening putty of this type had been used on tho work. Alternatively, the use of an excessive quantity of linseed oil would result in a soft putty for which tho normal small amount of hardening in tho form of a surface skin would be inadequate, particularly in steel sashes, since with these there is no absorption of the oil, as in tho case of wood sashes. The addition of gold size is sometimes made to increase tho rate of hardening of a putty. Though its use may be quite effective in this respect, its inclusion increases tho shrinkage of the putty, and the practice is one which cannot be recommended. “ For use in metal frames the addition of a hardening agent to a putty is desirable. White lead and red load arc often used for this purpose, and a good putty for glazing in steel sashes can be made by adding about 10 per cent, by weight of one of these substances to ordinary linseed oil putty, the desired plasticity being restored, it necessary, by a small addition of turpentine. If this mixture is used at a fairly stiff consistence—rather stiffer than that ordinarily used for glazing in wood frames—and the metal frames have been painted at least a few days previously, good adhesion and satisfactory hardening should result. After a few days the putty should receive one or two coats of paint, to give a surface hardness, and at the same time to prevent excessive hardening of tho underlying putty.”