2/2 TOWERS AND TANK'S FOR WATER-WORKS. 



but it is rare that such conditions exist, and, if necessary, can 

 be met by special requirements. 



"It is recommended that tests be adapted to the demands 

 of service conditions and divided into three broad classes: 



" i.' Actual service tests, under normal conditions, applied to 

 structure to be protected. 



" 2. Accelerated tests, applied to specially prepared surfaces; 

 and subjected to abnormally severe conditions. 



"3. Chemical tests to determine the constituents and adultera- 

 tions of the pigment and vehicle, as far as the knowledge of the 

 subject will admit. 



"It is undoubtedly true that the first set of tests gives the de- 

 sired information in a most conclusive manner, but, unfortunately, 

 the truth comes too late to remedy the evil if the protection is 

 insufficient to prevent corrosion. 



" It is further considered that the function of this committee 

 is not to specify any covering or coverings as protective, but to 

 specify tests which coatings must stand to assure maximum 

 efficiency. It will therefore be necessary to work along the 

 lines of accelerated and chemical tests, selecting those which 

 harmonize with the results of long-time service experiments, 

 and ultimately formulating laboratory tests which can be relied 

 upon to give the desired information. 



" It should, however, be realized that in this work chemical 

 analysis must be used to supplement experience, not to provide 

 it. In general, it is known by previous experiments that certain 

 pigments and oils give durability and protection, while others 

 fail in these essentials; but it will not do to condemn the unknown 

 without the aid of experience. 



" A review of the suggested accelerated tests shows a variety 

 of methods to impose abnormally severe conditions. Th< M- 

 tests have in some cases little connection to service requirements, 

 but it is believed that the results obtained by the methods selected 

 will be in harmony with long-time service tests. 



