FOULING GRADES 



To aid in judging the extent of fouling, pho- 

 tograplis shoving all but "negligible" fouling are 

 reproduced as figures 13-16. The grades estab- 

 lished by these photographs may seem rather se- 

 vere, but it should be emphasized that any foul- 

 ing in a given area represents a partial failure 

 of the paint. The percentage of film area that 

 is ineffective is more important than the total 

 weight or thickness of the fouling. 



When the fouling is evenly distributed over a 

 hull (not concentrated in definite patches) , the 

 grading should take into consideration the fact 

 that such areas may soon become fouled complete- 

 ly, either by the enlargement of the present im- 

 perfections of the film, or by the attachment of 

 additional fouling upon that already in place. 

 Uniformly distributed fouling indicates that the 

 fault probably lies in the formula of the paint, 

 whereas "patchy" fouling indicates improper mix- 

 ing during manufacture or application. (The grat- 

 ings in the table on page 2 of the docking report 

 contemplate the greater likelihood of "patchy" 

 fouling.) The following scale will help to cor- 

 relate these gradings for both situations. 



PERCENTAGE OF GIVEN CORRESPONDING GRADE 



AREA UNIFORMLY FOULED OF "PATCHY" FOULING 



0-5^ "negligible" 



5-10^ "in isolated small spots" 



10-20^ (fig. 17) "in large patches^' 



20-50% (fig. 18) "covering larger part of area" 

 50-100^ "covering area completely" 



26 



