NET PRESERVATIVE TREATMENTS 43 



A preservative for pound or trap nets, which gives promise of a 

 higher resistance to vegetable growth, consists of the following 

 ingredients : 



I'ounds 



Coal tar 62 



Wood tar 31 



Red oxide of copper 7 



The red oxide of copper should be " Navy standard," that is, con- 

 taining not less than 88 per cent cuprous oxide and fine enough so 

 that 98 per cent can be sieved through a 350-mesh screen. This 

 should be added last in making the mixture. The mixture sliould be 

 stirred while the net is being treated. 



Another preservative treatment for pound or trap nets, which 

 leaves the webbing more pliable and resistant to abrasion, consists 

 of the following ingredients : 



Pounds 

 Coal tar 50 



Copper oleate 15 



Benzol (4% gallons) 35 



Copper oleate containing not less than 8 per cent of copper should 

 be used. Benzol is highly inflammable and slightly poisonous, so 

 that extreme caution should be used in handling this mixture. Ordi- 

 narily, in warm weather, the mixture can be effected without heat. 

 In cold weather to make the mixture it may be necessary to heat the 

 kettle containing the mixture with a closed steam coil. In all events 

 the mixture should he kept wway from of en -fires at oil times. 



A. most satisfactory preservative treatment for producing a light- 

 weight pound or trap net consists of the following ingredients : 



Pounds 

 Coal tar , 12 



Wood tar 6 



Red oxide of copper 5i/^ 



Water gas tar oil (9 gallons) 76i/^ 



Red oxide of mercury (2 ounces) % 



The oxide of mercury should be as fine as possible and should be 

 ground thoroughly together with the red oxide of copper before they 

 are added to the other ingredients. The water gas tar oil is a by- 

 product of the coal-tar industry and ordinarily may be obtained from 

 the refiners at a cost of about 25 cents per gallon in 50-gallon 

 drums. This material is about as inflammable as kerosene and 

 should be handled with reasonable caution. Mixtures containing it 

 should be used at a temperature well above blood heat (about 150° 

 F.) to insure complete solution of the solvent components. In using 

 the above mixture, clean dry webbing should be immersed for at 

 least five minutes with constant agitation of the mixture to insure 

 against settling of the heavy solids. To guard against this, it has 

 been found excellent practice to operate a bilge pump in the center 

 of the kettle or tank in order to draw the mixture from the bottom 

 of the tank and distribute it over the section of the net being treated. 



This treatment has produced webbing which, under adverse con- 

 ditions, has maintained full strength for one year without fouling, 

 although it should not be inferred that similar results will always 

 l)e obtained. The only objection to this treatment is that the webbing 

 has a comparatively low resistance to abrasion. 



