A Decexxtat- Kecokd 29 



alone is treiiiendoiis. Preservation with creosote has been practiced 

 for many years, but not always with success. The laboratory has 

 made extensive studies on the resistance of various tars and creosotes 

 and their fractions to marine borer attack, and has collected numerous 

 service records. The i^roblem is by no means solved, however, and 

 many related factors such as temperature and sahnity of water, avail- 

 able food supply and other biological aspects of the question need fur- 

 ther study and correlation. A great deal of study must also be made 

 upon the various constituents of creosote and their relative effective- 

 ness. 



The discoloration of the sapwood, principally of pine, which is 

 commonly known as "sap stain", is considered a defect in most grades 

 of finishing lumber, and causes much loss from degrade. Various 

 improvements in chemical dipping to prevent sap stain have been 

 developed at the laboratory, and experiments have been made show- 

 ing that proper kiln drying will obviate the staining. 



An objection frequently raised against creosoted wood block 

 pavements is that the creosote oozes from them in warm weather, pro- 

 ducing a very disagreeable and dangerous surface. After a study of 

 the various factors involved and the making of a number of experi- 

 mental preservation runs on wood blocks, a method was evolved 

 whereby tlie observation of certain precautions in the process resulted 

 in reducing to a minimum the o])jectionable "bleeding" common up to 

 that time. In the drawing of specifications adopted by the American 

 Wood Preservers' Association and the American Society for ^lunici- 

 pal Improvements, for the treatment and laying of w^ood })locks in 

 })avements, the laboratory played a prominent part. 



Knowledge of the toxicity and preservative value of different 

 kinds of preservatives, both proprietary and otherwise, is fundament- 

 ally necessary, so that the good ones may be developed and the poor 

 eliminated. The laboratory has made tests on and analyzed practi- 

 cally all the important preservatives which have been on the market 

 since its inception. 



Fundamental information concerning the relative ease of treat- 

 ment with preservatives has been obtained for all of the woods ordi- 

 narily treated in this country. An important commercial application 

 of this information lies in the grouping of woods for treatment. 



