97 



coatnl whilr ik-aii and dry witli h(it as|)liall, i;i-ack' D, on jiiK' 14, 1920, was pulk'd on 

 Octol)iT KStli foUowini;, and found lo \k- hua\ily attacked 1)\' tereck) to a depth of as 

 much as two inches. It was pkiinh' apparent that the tere<k) liad ahiiost e\-erywhere 

 gone through the asplialt coating itself, and not simply tlirough abrasions or other 

 accidental openings in it. On another pile, wIktc the action ol (he asphalt itself could 

 be better observed by reason of the pile i)eing wrapped with burlap saturated with 

 the asphalt, the latter was found to have emulsified during the three months, in the 

 outer four ol twelve layers. 



Paints Ai,one 



A considerable number of hydrocarbon com])ounds intentled lor brush a|)])lication 

 are now being acti\'ely promoted, in which the hydrocarbon base has been so treated 

 chemically that it remains viscous and elastic almost indefinitely, and to which have 

 been added various poisonous constituents to kill any animal or \egetable growth 

 which attempts to penetrate them. The promoters of such suriace applications which 

 have no additional mechanical reinforcement or protection, forget, howe\er, the 

 battering of vessels, or of driftwood under storm action, to tlie hazard of which a pile 

 in service is subjected as well as to the boring animals. As soon as any portion of the 

 paint protection is thus removed a door is thrown wide open to the borer. None of 

 these methods has been given any real experimental trial in San Francisco Ba\-, 

 although in exjx'riments elsewhere some of them are said to have resistetl ship-worms 

 o\er periods during which untreated w^ood beside them was destroyed. 



"Paint and Battkn" Methods 



A great variety of protections ha\e been suggested and tried in San Francisco 

 Bay, which consist of some heavy paint such as has lieen described, usually combined 

 with special poisons, and applied in combination with burlap, felt, roofing paper, 

 wire mesh, w^ood battens or other materials. The object of these combined materials 

 is to reinforce the paint coat, and make it less likely to be broken or torn off. The 

 protections of this class differ among themseh'es as to the nature of the paint employed 

 and the materials and methods used in apphing the reinforcement. The details and 

 methods of apphing any one of them have also varied somewhat from time to time 

 as market conditions, opinions of engineers and the experience gained in placing the 

 protection, dri\-ing the piles and ol)ser\ing their l>eha\ior have indicated that 

 changes were desirable. They are all similar in jirinciple, howe\-er, and possess 

 similar advantages and disadvantages.* 



The chief advantages of paint and batten coatings are their relati\e cheapness, 

 ease of application and the possibility of limiting the protection to the part of the 

 pile exposed to the borers. It has been common practice to apply the coating so that 



*The Committee understands that this general method of protection is not patented. This under- 

 standing is based in part upon the following statement which was made a number of years ago by one 

 of the interested companies; 



"The materials used by us are not patented, nor is the method, although both materials 

 and methods were patented. The patent on the materials has expired, while that on the 

 method was declared invalid, hence materials and method are open to the world." 

 From this it would appear that, aside from the patents which ma\- still exist on certain recentU- devel- 

 oped formulae for prepared paints, this method of protection is available for the use of anyone. The 

 Committee has not attempted to investigate the patent situation, however, and does not pretend to 

 speak with authority on this subject. 



