PRESERVATION OF FISH NETS 411 



EXPERIMENTAL EXPOSURE AND TESTING OF LINES 



Eight series of experiments were undertaken, some of which were 

 for the purpose of determining the effects which various preservatives 

 would have in the several geographical regions chosen and others 

 were for the purpose of obtaining certain special information which 

 could best be obtained at the particular location chosen. These 

 regular and special tests will be described later in connection with the 

 experiments. The cotton twine used throughout the experiments 

 was No. 24 cable-laid, hard-finish; the linen line was 10-ply 40, Irish 

 flax, salmon thread, and the hemp was 2-ply manila lobster marlin. 



NOTATION OF SAMPLES 



Cotton lines 



A Untreated — used as a control. 



EE Copper oleate — 15 per cent concentration in gasoline. The lines were 



dipped into this solution and allowed to become thoroughly saturated. 

 This required but two or three minutes. The lines were then removed 

 and spread out to dr,y (not piled in a heap) . 



FF Copper oleate, to which was added 25 per cent of paraffin (by weight)— 



15 per cent concentration in gasoline. Applied same as EE. 



GG Copper oleate, to which was added 15 per cent of boiled linseed oil (by 



weight) — 15 per cent concentration in gasoline. Applied same as EE. 



HH Copper oleate, to which was added 15 per cent of raw linseed oil (by 



weight) — 15 per cent concentration in gasoline. Applied satne as EE. 



L Quercitron and ammoniacal copper sulphate (called Dutch method in 



former paper). The lines were steeped in a hot solution of quercitron, 

 1 pound to 2 gallons of water, until the solution was cold, dried, 

 again steeped in the same way, and again dried. They were then 

 immersed for a few minutes in an aminoniacal solution of copper 

 sulphate containing 1 pound of copper sulphate and 3 pounds of 25 

 per cent ammonia for every 12^^ gallons of water. For a full descrip- 

 tion of this method see Olie (1918). 



JJ This is a proprietary waterproofing substance manufactured and sold 



under a trade name. It is especially recommended as a mildew 

 proofing for canvas. The product is ready for use as purchased from 

 the manufacturer and is applied by immersing the twine in the solution 

 for a short time, then removing and allowing it to dry. 



KK Coal tar. The coal tar used for these experiments was slightly lighter 



than that used in 1922. (The specific gravity was about 1.16.) 

 Equal weights of this tar and benzol were mixed, the benzol thinning 

 the tar sufficiently so that no heating was necessary. The lines were 

 immersed in this mixture, surplus tar removed by passing them be- 

 tween the fingers, and the lines strung up to d^J^ It should be 

 noted that this is not the commonly used method of tarring nets. 

 They are usually drawn through hot tar. 



LL This is a proprietary wood and twine jDreservative sold under a trade 



name. The lines were steeped in the solution two hours, then 

 removed and dried. 



MM Azulmic acid. The dye was dissolved in N/10 sodium hydroxide solu- 

 tion and the twine immersed in this solution for two hours in the cold. 

 The twine was then rinsed in pure water containing a very small 

 amount of hydrochloric acid. 



RE Rare earths. Samples of twine were treated by a company having a 



special process for waterproofing materials with certain rare-earths 

 compounds which they believed would have a preservative effect. 



RC Rare earths and copper oleate. Samples of twine that had been treated 



by the rare-earths process were treated with copper oleate in the 

 regular way, the same as EE. 



Y This preservative is a mixture of 50 per cent coal tar, 35 per cent 



benzol, and 15 per -cent copper oleate (each by weight), applied 

 same as KK. 



