EVALUATION OF WOOD PRESERVATIVES 



447 



creosotes in these groups, the differences are not at present real and 

 tangible because they are masked by other factors, among which distri- 

 bution of the preservative, and retention and penetration variables seem 

 most important. The over-all indications are that in general one should 

 insist on something more than 8, and probably more than 9, pounds of 

 creosote per cubic foot, at the time of treatment, in the outer inch of the 

 ground section of a southern pine pole. This, in simple terms, is in line 

 with the conclusions reached about threshold retention requirements 

 from the laboratory tests of creosoted J^-inch cubes and from test plot 

 results on J^-inch stakes. 



It is much harder to rate treated test posts in terms of per cent condi- 

 tion than it is to rate small specimens. Fig. 28 must be considered there- 

 fore as a generalization from the plot inspection data. It must be inter- 

 preted with the help of Fig. 27 and the retention by zones data in Tables 

 XV and XVII. The reader who is at all familiar with pole line service 

 records will recognize how much more detailed information there is for 

 these test posts than there generally is for the ordinary pole hne. Yet it 

 is practically impossible to draw up precise, unequivocal statements 

 about the results in certain of the post series. The conclusions must be 

 broad. 



The structure of the wood in a pole, the distribution of moisture con- 

 tent, the variation in density of the wood from the outside to the inside 

 annual rings, and the distribution of creosote from the outside toward 

 the inside all go to make up a resultant that is obviously complicated. 

 Some of these factors have been reduced to a schematic figure (Fig. 29) 



Table XVII — Creosoted Southern Pine Test Posts 

 Relation between average treatment retention in outer inch of sapwood and 

 condition of posts at the 1950 inspection; Gulf port test plot. 



* All calculations are made on the basis of an 8-inch diameter at the point of 

 sampling. 



