FORESTRY AND CONSERVATION 403 



under, and curling or warping results. The importance of exclud- 

 ing moisture is obvious. In addition to this, it is advisable to em- 

 ploy an antiseptic to retard decay. The best preservative, it follows, 

 must possess such qualities as will operate in both these ways to 

 prolong the life of the shingles. The necessity of applying preserva- 

 tives only when the wood is thoroughly dry may again be empha- 

 sized. 



Nonantiseptic Preservatives. The application of paint is the 

 preservative measure most commonly used with shingles. The 

 method of applying it is of paramount importance. Dipping the 

 shingles individually is the only satisfactory procedure. When a 

 roof is painted ridges of paint are formed at the bases of the shingles, 

 owing to the irregularities of the surface over which the brush passes. 

 These cause the water to permeate the crevices between the shingles 

 and frequently hasten decay. 



Antiseptic Preservatives. The best antiseptics for shingle treat- 

 ment are creosote and other derivatives of coal tar. Painting the 

 roof with these oils is a rather satisfactory method of treatment, since 

 the coal-tar derivatives penetrate the shingles better than ordinary 

 paint and do not leave ridges below the base of the shingles. At least 

 two coats should be applied. Dipping the individual shingles gives 

 good results. The best results are, however, obtained by heating 

 and cooling the wood in the preservative, as described for the treat- 

 ment of fence posts. Sap loblolly pine shingles may be thoroughly 

 impregnated by means of the open-tank process. This method is 

 the best even for woods which resist the penetration of the oil; for 

 example, white cedar. Its advantages are two-fold the shingles 

 can be treated in bundle form, and, with proper treatment, the 

 surface of the wood will be free from surplus oil. 



The open-tank process has already been explained. The ap- 

 paratus used for posts may be employed, or if shingles exclusively 

 are to be treated the form of the outfit may be modified. The 

 simplest apparatus is a single tank large enough to hold a bundle of 

 shingles. If a larger capacity is desired, the depth rather than the 

 width should be increased, for, in order to minimize the loss from 

 volatilization, the oil surface exposed to the air should be kept as 

 small as possible. The best treatment for various kinds of shingles 

 has not yet been determined. The proper length of treatment may, 

 however, be readily decided in any particular instance by weighing 

 the shingles before and after treatment. An obsorption of 12 or 

 13 pounds per bundle, or 6 gallons per thousand shingles, is advis- 

 able. The cost of treatment per thousand shingles should range 

 from $1.25 to $1.50. In order that the deepest penetration com- 

 patible with this absorption may here be secured, the heating should 

 oe relatively long. 



Creosoted shingles possess certain objectionable qualities, though 

 none which prohibit their use. Among these may be mentioned their 

 strong odor and their contamination of cistern water. Further, 

 since the shingle nails become covered with creosote and can not be 

 held in the workman's mouth, it is said to be more difficult to lay 



