This copper is often called hot-rolled copper and is used for lining gutters, valleys, etc. and for pressed or hammered ornaments. The weight generally specified is 16 ounces, and 18 or 20 ounces on such work as may be subject to much wear and tear, either by expansion and contraction or by rough usage.

Soft copper, tinned on both sides, is best adapted for gutters and all other work which depends upon solder for tightness and strength. Copper cleats should always be cold rolled.

81. All sheet-metal seams should be soldered very slowly, because it takes time to properly sweat a seam; and very hot, well tinned soldering irons should be used.

Any mechanic discovered "rushing" a seam or hastily skinning it over with solder should be immediately discharged and all his work should be resweated by a careful man, as the durability of sheet-metal work depends chiefly upon the soldered seams.

Resin should be used as a flux for all tinned copper, and chloride of zinc for all plain copper, galvanized iron, and zinc. Raw muriatic acid or sal ammoniac should not be used as a flux.