BRUSH AND TANK POLE TREATMENTS. INTRODUCTION. The preservative treatment of railroad ties and piling has been practiced commercially for a number of years. About fifty treating plants are now being operated in this country, and the number increases each year. The treatment of telephone and telegraph poles has made no such progress, yet there is a strong desire on the part of progressive users to find a satisfactory method for prolonging the life of poles. From time to time experiments have been conducted by various telephone, telegraph, and railroad companies, but either the treatment was faulty or insufficient records of the treated poles were kept, and, as a result, neither reliable data nor satisfactory conclusions have been obtained. In some cases the whole length of the pole has been treated in closed cylinders, but this expensive treatment is used only on poles to be set where the top as well as the part in the ground is subject to rapid decay. Often preservatives have been applied to the butt of poles with a brush, and when the poles were seasoned doubtless much good was accomplished. But when the oil had been applied to the outside of green, freshly cut poles they were found to decay practically as soon as untreated poles. Thereupon the preservative was declared valueless, and the experiment considered as proof that poles could not be satisfactorily treated by that method. Consumers of poles are generally of the opinion that present conditions do not warrant a very large outlay for treatment; nevertheless, because of the diminishing supply, they demand that the length of service be increased. That seasoned wood is more durable than green in contact with the ground is generally admitted, but how much more is not known. Many also hold that wood which has been soaked in water is more durable than that which has not been soaked, but here again definite proof is lacking. For these reasons the Forest Service has undertaken to determine what treatments are most effective and what expense for treatment is justified by the resulting increased service. Circular 103 presented the results of experiments to determine the rate of seasoning of telephone poles. Mention was there made of a [Cir. 104] series of experiments to determine the effect of various preservative treatments in delaying their decay. The present circular describes the experimental treatments of these seasoned poles by the brush and by the open-tank methods. The latter is a new method developed by the Forest Service and promises excellent results in treating poles cheaply and effectively. PLAN OF THE EXPERIMENTS. The experiments were planned not only to afford data on the relative increase of life of treated over untreated timber, and on the value of different preservatives, but also to determine the effect upon the durability of poles of air seasoning, and of soaking in water with subsequent air seasoning. The large question to be answered is, What is the best method of increasing the length of service of poles? This question, however, is very complicated and its answer can only be arrived at by answering a number of other more simple questions upon which it depends. The questions which these experiments are designed to answer are as follows: 1. What advantages have seasoned over unseasoned poles in taking treatment? 2. What is the increase in length of service of seasoned over green poles, both when untreated and treated? 3. Does submersion in water, with subsequent air seasoning, render poles more durable or easier of treatment than simple air seasoning? 4. Does the season of cutting affect treatment? 5. What preservatives are easiest of application and most effective? 6. What method of application is best? Of these questions, 2, 3, 5, and 6 can be answered, in whole or in part, only after the lasting qualities of the poles have been tested in actual use. This test has already been begun by setting the poles in an experimental line; but some years must elapse before results will be obtainable. The present circular presents the information gathered in the course of administering the treatment, and throws light on the capacity of poles-green, seasoned, and soaked-to absorb preservatives, the degree of penetration secured with different preservatives, and the comparative cost of treatment by the brush and the open-tank methods. To show what has been done to arrive at final conclusions as to the comparative effects upon durability of the different preservatives and different methods of handling and treating, there is appended a description of the experimental lines in which the poles have been set. Seven preservatives were used in the experiments. All of these are regularly sold on the market for preserving wood and most of them are protected by patent or trade-mark. All the preservatives are more or less modified distillates of coal tar or pine tar. Except for the preservative designated (D), which is common creosote or dead oil of coal tar, the names of the different preservatives are not given, but their composition is given in Appendix I. With one or two exceptions, the unnamed preservatives were given by the manufacturers for use in these experiments. METHODS OF TREATMENT. Two methods were employed in applying the preservative to the poles. On the larger number of poles the preservative was applied to the outside with a brush, allowing it to soak into the wood through its own power of penetration. All the different preservatives were tested by this method. The second method was to soak the butts of the poles in hot preservative in an open tank. In this method only one preservative, the dead oil of coal tar (D), was used. BRUSH TREATMENT. It is generally conceded that the portion of a pole most subject to decay is that between 2 and 8 feet from the butt-about 20 square feet. This part fails when the remainder is still in a good state of preservation. It was therefore selected for treatment. When the pole is set the treated portion extends 2 feet above and 4 feet below the surface of the ground. From one to three coats were applied, according to directions received from the manufacturer. Most of the preservatives were heated to a temperature of from 150° to 175° F. Particular attention was paid to filling all checks and knot holes and to working the preservative into the wood, thus protecting against decay those parts most subject to attack. Careful notes were made of the condition of the poles as regards checks, knot holes, etc. The amount of preservative absorbed by each pole was accurately determined by recording the weight of the preservative before and after each treatment. The temperature of the preservative both before and after the treatment was also noted and recorded. In addition holes were bored into different parts of the treated portions of the poles, and the depth to which the preservative penetrated was closely observed. OPEN-TANK TREATMENT. The device for the open-tank process consisted of a steel tank resting on stone or brick walls in such a manner that a fire could be placed beneath it. The top of the tank was rectangular in shape, about 11 feet long and 6 feet wide. Its depth was about 4 feet at one end, tapering gradually to zero at the other. A vertical cross |