vehicles and used as a protective coating on iron and steel, is not justified. In order to make this point quite clear, it has been agreed by the Committee to qualify the classification so as to speak of the various materials tested as 'water stimulative' or 'water inhibitive.'" [Illustration: Apparatus for Testing the Inhibitive Value of Pigments] =Importance of Field Tests.= Although the laboratory accelerated tests for the determination of the relative value of structural steel paints afford information of some import, there seems to be a general opinion that the best method to follow, if information of a reliable character is to be obtained, is to make actual field exposure tests upon large surfaces. The results of the above described water-pigment tests suggested the erection of a series of steel panels on which to test out the same pigments under practical service conditions. The Paint Manufacturers' Association of the United States erected and painted the panels, the work being under the constant supervision of the writer, and the inspection of the work under Committee U of the American Society for Testing Materials. A brief resume of the work[39] is herewith presented. [39] Page 181, "Corrosion and Preservation of Iron and Steel"--Cushman and Gardner--McGraw-Hill Book Co., New York City. =Pickling and Preparation of Plates.= The three types of metal[40] selected for the test were rolled to billets, the middle of which were selected, and worked up into plates 24 inches wide, 36 inches high, and 1/8 inch in diameter--approximately 11 gauge. A number of plates of each of the metals selected, in all 450, were pickled in 10% sulphuric acid, kept at 180 to 200 degrees Fahrenheit, in order to remove the mill-scale. The plates were then washed in water, and later in 10% solution of caustic soda. Finally the plates were again washed in water and wiped dry. They were then packed in boxes containing dry lime, in order to prevent superficial corrosion. By this method the plates were secured in perfect condition, the surfaces being smooth and free from scale. Upon these pickled plates paints were applied with a definite spreading rate of 900 square feet per gallon. The unpickled plates, coated with mill-scale, were painted with the same paints, but without adopting any special spreading rate, thus following more closely the ordinary method of painting structural steel. A few extra plates of special Bessemer steel and Swedish charcoal iron were also included in the test, some of which were painted, while others were exposed without any protective coating. Plates of the three types of metal already mentioned were also exposed unpainted, both in the black and pickled condition. [40] Bessemer Steel, Open Hearth Steel, and Pure Iron. [Illustration: Front View of Steel Test Fences]