PRESERVATIVE TREATMENT OF FENCE-POSTS UC-NRLF A eric . - Forestry . M am Libran n't! iff 'flu DEPARTMENT OF THE' I Is] TEillG R FORESTRY BRANCH CIRCULAR No. 6. If. IT. CAMPBELL, Director of Forestry. RESERVATIVE TREATMENT OF FENCE-POSTS R. G. LEWIS, B. Sc. F. OTTAWA GOVERNMENT PRINTING BUREAU 1913 DEPARTMENT OF T.ES I^TiEKI FORESTRY BRANCH CIRCULAR No. 6. E. H. CAMPBELL, Director of Forestry. PRESERVATIVE TREATMENT OF FENCE-POSTS R. G. LEWIS, B. Sc. F. OTTAWA GOVERNMENT PRINTING B U S E A TJ 1913 401 101 Agric. -Forestry. Main Library CONTENTS. PAGE. Introduction 5 Choice of Preservative 5 Choice of Material 8 Preparation of Material . . . * 8 General Object of Treatment 8 Brush Method 9 Open-tank Method ' 9 ILLUSTRATIONS. Piling Posts for Seasoning (Fig. 1) 6, 7 Methods of Bevelling the Tops of Posts (Fig. 2) 6, 7 Home-made Plant for Treating Fence-posts (Fig. 3) 10 Heating Tank (Fig. 4) 6, 7 Cooling Tank (Fig. 5) 6, 7 519067 461102 3 PRESERVATIVE TREATMENT OF FENCE-POSTS. The supply of durable woods for fence-posts in Canada is rapidly decreasing, and with this decrease comes the inevitable increase in cost and reduction in quality and size of material. Cedar is, at present, the most abundant native wood that is at all durable in contact with moist soil. The supply of posts of this material is rapidly nearing exhaustion. Oak and chestnut are durable, but these woods are so scarce and so valuable for other purposes that they are not used extensively for posts. Canada, however, is fortunate in possessing an abundance of the less durable woods such as poplar, jack pine, spruce, balsam fir and willow which are more readily treated by preservatives than the denser hardwoods. Where the cost of cedar and other durable woods becomes excessive, the use of inferior woods becomes necessary. Where posts of these woods decay rapidly, the cost of replacing them becomes an expense, no matter how cheap the material may have been. It is, then, necessary to calculate the actual saving that could be accomplished by treating such material with a preservative of some sort to prevent or retard decay. Before deciding on such an action it is necessary to consider all the factors that enter into the cost of fence maintenance. These include the first cost of the post, the cost of peeling and seasoning, the cost of transporting from the source of supply to the place of setting arid the cost of setting the post; in the case of treated posts, the cost of treatment must also be included. In order to get a fair comparison of treated and untreated posts, all these different items must be added, and the total cost divided by the number of years the pole will last in order to arrive, roughly, at the cost per year (annual cost) for the post. With untreated material, to the initial cost of the post is to be added the cost of seasoning, transporting from the source of supply to the farm and putting the post in place. With treated material the initial cost is usually lower, as inferior species can be used. The cost of transportation is usually lower, as local supplies are available. The cost of peeling and seasoning may be higher, as posts must be peeled and well seasoned before they can be properly treated. The cost of treatment will be the most important item and will depend on the preservative used and the treatment adopted. The cost of placing the post will be less as an annual charge because the post will last longer and will not need to be replaced so often. All these cost items can then be considered in relation to the increased life that the treatment will cause. The annual cost of each post will be found to be much less for treated material than for untreated in the majority of cases. Preservative treatment of fence-posts has been experimented with under a multi- tude of different conditions, and the results recorded. A summary of these results indi- cates that an enormous saving in actual dollars and cents can be accomplished by the use of proper preservative treatment. CHOICE OF PRESERVATIVE. Experience has shown that creosote, or deal oil of coal tar (or some of the patent preservatives with this substance as their base) is the most satisfactory preservative for wood which is to be used in contact with moisture. There are two primary reasons u: i 1 8 ^ FORESTRY BRANCTl" CIRCULAR NO. 6. for this. Creosote is a chemical poison to the different organisms or fungi that cause decay in wood and also to the different insects that destroy it. Creosote is a heavy oil, insoluble in water. If it can be forced into the substance of seasoned wood it prevents the further absortion of water. Moisture and air are necessary for the growth of fungi and if wood can be kept dry it will last indefinitely. There are many substances such as zinc chloride, mercuric chloride, copper sul- phate and others that are poisonous to fungi and insects, but these are all soluble in water and when used as wood-preservatives must be dissolved in water. "Whenever the wood so treated comes into contact with moisture, the preservative will dissolve again and leach out, leaving the wood liable to attack by the agents of decay. Creosote is a by-product obtained in the manufacture of coal gas and is a more or less variable substance. The denser the oil, the more difficult it is to force it into the wood, but the less likely it is to evaporate, either during the process or after it has pene- trated the wood substance. The lighter the oil the deeper the penetration, but the higher the loss by evaporation. The oil can be obtained in almost any large city where coal gas is manufactured, and costs in Canada from 10 to 25 cents a gallon, depending on quality, density, trans- portation charges and quantity purchased. CHOICE OF MATERIAL. The choice of material to be treated will depend largely on local conditions of supply. In the Maritime Provinces the most economical woods for treatment will prob- ably be spruce, hemlock and balsam fir ; in Quebec and Ontario, spruce, hemlock, balsam fir and jack pine; in the Prairie Provinces, poplar, jack pine, spruce and willow; in British Columbia, lodgepole pine, western yellow pine, and poplar. One of the chief advantages of preservative treatment is that it makes possible the use of the cheaper class of local woods and the choice of material will depend on the initial cost and the cost of treatment of such woods. PREPARATION OF MATERIAL. Whatever material is chosen for fence-posts a thorough seasoning is a primary necessity. The posts should be cut in the spring as soon after the buds begin to swell as possible. The bark an then be removed most readily. Posts should be carefully peeled, and special care taken to remove the thin inner bark, or bast, as this, if left, prevents the absorption of the preservative. Figure 1 shows a method of piling posts for seasoning which allows a free circula- tion of air. They are placed in alternate tiers of three and seven posts with about fifty in a pile and the piles should be at least ten feet apart. Posts cut and peeled in the spring and allowed to season through the summer are ready for treatment in the early autumn. Bound posts are preferable to split material as the preservative will, in the majority of cases, penetrate only the sapwood. The top of each post should be bevelled off as shown in figure 2 to shed the rain and prevent the top becoming water-soaked. GENERAL OBJECT OF TREATMENT. The general object of the treatment is to obtain as deep a penetration of creosote into the cells of the wood as possible with the least quantity of preservative and the least loss from evaporation during the process. PRESERVATIVE TREATMENT OF FENCE POSTS. 9 THE BRUSH METHOD. This is the least expensive method of applying creosote to fence-posts and is to be recommended only on account of its cheapness. Give the butts of the posts at least three coats of hot creosote with an ordinary brush. Heat the oil to boiling and keep it hot while applying each coat. Fill all cracks and checks carefully. Allow each coat to be absorbed before applying another. Stand each post on end, butt upwards, while drying, in order to allow any surface oil to run toward the top of the post. If possible, do the work in warm weather and in the sun. If the oil cools too quickly, or if the posts are cold, the oil will congeal on the surface and will not penetrate into the wood cells. If desired, a coat of oil can be applied to the entire post to prevent decay of the upper part. As a rule, it is necessary to paint only the butt of each post up to a point at. least six inches above the ground-line, as this is the part most liable to decay. This treatment usually results in a penetration of about one quarter (i) of an inch of creosote of ordinary density. This should add at least ten years to the life of a post of a non-durable wood such as poplar, balsam fir or spruce. THE OPEN-TANK METHOD. This is a more satisfactory method than that described previously, but it neces- sitates a more or less costly plant. The theory of the method is a simple one. The posts are heated in a hot bath of creosote which expands the air in the wood-cells and turns a part of the moisture in the wood into steam. This expansion forces out a certain part of the air and water in the wood. The posts' are then placed in a cooling tank, or allowed to cool in the heat- ing bath, and the contraction of the air remaining in the cells and the condensation of the steam produces" a partial vacuum that draws a certain quantity of preservative into the cells of the wood. The vessel or vessels used, the time taken in heating and in cooling and the details of the method generally will depend on the judgment of the operator and the cost of apparatus. Figure 3 shows an inexpensive " open-tank " plant that can be made on any farm. It consists of a tight barrel, three lengths of piping and the necessary couplings. Place a charge of posts in the barrel and pour in creosote until the upper arm of the piping is below the surface of the oil. Build a fire below the lower arm of the piping as shown in the sketch. Take care to screen the barrel from the fire, as the oil is very inflammable and can be easily ignited by a chance flame or spark. The heating will set up a cur- rent, and will gradually raise the temperature of the oil in the barrel to boiling point and keep it at this temperature. Do not allow the oil to reach a higher temperature than 220 F., or the loss due to evaporation will be excessive. This loss will vary from ten to twenty per cent in any case, depending on the density of the creosote. Leave the posts in this bath until no more bubbles rise to the surface of the oil. This time will vary according to the nature of the wood used and the extent of its previous seasoning and should run from one to six hours. The time taken will vary under different con- ditions and should depend on the judgment of the operator. A few trial charges of posts will show the most economical time. After the heating is completed, withdraw the fire and allow the oil to cool. Leave the posts in the cold oil from half an hour to four hours, or until a sufficient penetra- tion has been obtained. This can be determined by trial only as different conditions will have different effects on the result. After the cooling is completed allow the posts to drain off by placing them in an empty barrel, butts upward. The excess of oil can then be collected and used over again. This method permits of many variations in procedure and in apparatus used. The posts may be removed from the heating bath at the completion of the heating and 10 k 'FORESTRY "BRANCH 'CIRCULAR NO. 6. PRESERVATIVE TR^A^^Tr^^T* b^P^'C^O^'DS. 11 placed in a separate barrel containing cool creosote and left in this barrel until the necessary penetration is obtained. The heating barrel can then be recharged imme- diately, and the process made a continuous one with little or no loss of time. A wooden tank long enough to hold the posts lying on their sides completely submerged can be used as a cold bath. The butts, having been heated the most, will absorb the most creosote and the tops will take up a comparatively small quantity, producing ideal con- ditions to withstand decay. Some of the more perishable woods such as poplar, willow, maple and scrub oak require this additional top treatment. The same result may be obtained by applying the open-tank method to the butts and a brush application to the top parts of the post. The above apparatus is quite good enough for a small number of posts. Where large quantities are to be treated the plant should be of a more permanent nature. The wooden barrel will leak and the joints cannot be kept absolutely tight. A galvanized iron barrel or tank can be substituted for the wooden barrel and these difficulties over- come. There is a considerable waste of heat and a danger of igniting the oil in the use of the open fire. If a heavy metal tank is used in place of the wooden or galvanized iron barrel, a fire can be built directly beneath it and the fire kept under control by building a stone or brick fireplace with a stove-pipe chimney. Where steam is avail- able, galvanized iron can be used and coils can be placed in the bottom of the tank to heat the creosote. This removes the fire danger and keeps the oil at a constant tem- perature with a reduced loss due to evaporation. Figures 4 and 5 show a complete open- tank apparatus with steam connections. The piping in the cooling tank is used to admit steam in cold weather when there is a danger of the creosote solidifying. Many modifications of this apparatus and of the method outlined will suggest themselves to the operator who can adapt them to his requirements. MAR 23 1931 APR 2 41953 Li YD 02930 Irnnnr:" UNIVERSITY OF CALIFORNIA LIBRARY