FOULING OF SHIPS' BOTTOMS 233 



The effects of many kinds of commercial paints have been observed during this 

 investigation, but not in sufficient numbers to make it advisable to contrast their 

 effectiveness, except in the comparison with the "Norfolk standard" used by both 

 the Navy and the Shipping Board, whose vessels comprise more than 90 per cent of 

 those examined in this investigation. It can be stated, however, that no paiat, with 

 the possible exception of "Moravian" {LitchHeld, April 10, 1924), has proved to be 

 superior to the "Navy standard." The "amalgamated" was used on the Benguela 

 (September 4, 1924), and this vessel was much more severely fouled than the West 

 Hestleton (August 12, 1924), both of which, as seen from their records, had similar 

 duties, cruising records, and itineraries, and were operating at almost the same 

 season of the year, a factor that may have had some influence. 



The effect of the "Red Hand" paint was seen on such ships as the HopTcins 

 and Kane (December 7, 1923), Gof and Gilmer (November 21, 1923), and Fox 

 (April 10, 1924), as well as on others; but adequate comparisons could not be made. 

 In several cases, however, similar ships with similar duties but with "Navy standard" 

 paint showed somewhat less fouling than the above. 



The "International" paint was used on several lightships and tenders, includ- 

 ing the Relief (April 24, 1924), NortJiend (June 2, 1924), Lotus (August 7, 1924), 

 Hawthorne (March 10, 1925), and LightsMp 108 (April 4, 1925), and in most cases 

 these were badly fouled. No comparison could be made, as none were painted with 

 the "Navy standard." 



The problem of continued effectiveness of paint is one that has been pondered 

 long. The number of factors that enter into the problem of fouling apparently have 

 clouded any accurate determination of this matter; and even in this investigation 

 with respect to only a few ships could the question be answered positively, as 

 negative data were inconclusive. 



In the case of the Maryland (October 12, 1922), a heavy set of barnacles had 

 occurred within the 70 days that elapsed after a previous dry docking, and in the 

 case of the Sturtevant (November 20, 1924), a similar heavy growth of Balanus 

 improvisus occurred during the 90 days after the previous dry docking. In the 

 few other cases of short docking intervals (usually occasioned by some accident to 

 the ship) Hght fouling, due to algse, was observed. It is evident, however, from 

 these two cases, as well as from the experimental test plates, that fouling frequently 

 occurs even within 20 days of the time of painting, indicating that the effectiveness 

 of the poisons apparently was lost by that time. 



Many steel panels coated with various poison paints have been submerged, both 

 by the Navy Department and by the American Society for Testing Materials, in 

 order to determiiie the relative efficiency of such paints as antifouling means. 



Although the final report on the experiments conducted by the Navy Depart- 

 ment has not been seen by the writer, the report of Bray (1923) contains a list of 

 many of the poisons used and the period of exposure when examined. These poisons 

 were used as ingredients of paint fibns and were employed in concentrations of 4, 8, 

 and 12 per cent. The following selections will give some idea of the range of materials 

 tested: HgO, ZnO, CuO, naphthalene, zinc cyanide, poke root, NaOH, cupric oxide, 

 sodamid, thymol, hydroxylamine sulphate, strychnine sulphate, quinine sulphate, 

 uranium nitrate, Portland cement, T. N. T., phenol, capsicum, arsenated bakelite, 



