In steam and hot-water heating the decoration of the radiators is a much more important item than that of a good-looking surface or one which will harmonize with the setting. Until recently radiator finishing has been considered a minor detail and the familiar bronze has been looked upon as a standard covering, while painted radiators were considered only a matter of taste. The character of the surface is, however, the determining factor in the quantity of heat given out by radiators. This has been determined in the experimental laboratory of the University of Michigan by Professor John A. Allen. Comparison was made of bare cast-iron radiators with the same forms painted as indicated in the following table. The bare radiator was taken at 100 per cent.; the other finishes are expressed in per cent. above or below that of the bare radiator.

Fig. 29. Ventilation by the indirect method of heating.

Fig. 29. - Ventilation by the indirect method of heating.

Fig. 30. Ventilation by the direct indirect method of heating.

Fig. 30. - Ventilation by the direct-indirect method of heating.

Condensing capacity, per cent.

No. 1, a cast-iron radiator, bare as received from the foundry

100

No. 2, a cast-iron radiator, coated with aluminum bronze.....................

78

No. 3, a cast-iron radiator, three coats of white enamel paint...............

102

No. 4, a cost-iron radiator,coated with copper bronze...........................

80

No. 5, a cast-iron radiator, three coats of green enamel paint.

101

No. 6, a cast-iron radiator, three coats of black enamel paint.

101

The author has stated further that, "It might be said in general that all bronzes reduce the heating effect of the radiator about 25 per cent. while lead paints and enamels give off the same amount of heat as bare iron. The number of coats of paint on the radiator makes no difference. The last coat is always the determining factor in heat transmission."