Januabt 14, 1909. 



The Weekly Florists' Review. 



11 



Government's Open Tank Method of Treatment of Timber with Wood Preservatives. 



(With Bligbt modification tbis will be employed in the experimental trea'ment upon greenbouse timbers.) 



numbers of these spores are borne and 

 thrown off into the air, which in turn 

 may attack wood and so continue the de- 

 structive work. 



In order that hese spores may de- 

 velop, they must have specific amounts 

 of water, heat, air and food; therefore 

 by reducing or eliminating any one of 

 these it is possible to prevent them from 

 developing. It will be readily seen that 

 in the interior construction of green- 

 houses, heat can not be eliminated. 

 Water may be kept away in some eases 

 and air in others, but it is probable that 

 the element which can be most readily 

 controlled is the food, or the wood 

 itself. This can be done by impregnating 

 it with some liquid which is poisonous 

 to the fungus and which will consequently 

 prevent its growth. 



Method of Treating Timbers. 



For such purposes the open-tank meth- 

 od is well adapted. This method is 

 based upon the use of an open tank, 

 capable of withstanding heat, and either 

 equipped with steam coils or so arranged 

 that fire can be placed underneath. 



Sufficient preservative is run into the 

 tank to coTer the portion of the timber 

 which is to be treated, and the tempera- 

 ture of the liquid is then raised slightly 

 above the boiling point of water. This 

 temperature is maintained for a length 

 of time depending upon the character 

 of the wood and the treatment desired. 

 At the end of the hot bath the timber 

 is either quickly transferred to another 

 vat, containing a cold preservative, in 

 which it is submerged for a definite 

 period of time, or else the heat is shut 

 off and the timber is allowed to remain 

 in the cooling liquid until the required 

 absorption is obtained or until no further 

 absorption takes place. The time re- 

 quired by the treatment may be short- 

 ened, without transferring the timber 

 from one vat to another, by running out 

 the hot liquid at the end of the hot 



bath and simultaneously letting in the 

 cold liquid. The vacuum is brought about 

 by alternate heating and cooling of the 

 wood in the preservative, and atmospher- 

 ic pressure is used to force the liquid 

 into the wood. 



Preservatives Employed* 



For all purposes the most effective 

 preservative in general use today is 

 creosote, or dead oU of coal tar. How- 

 ever, it probably can not be used in 

 treating all classes of greenhouse timbers, 

 because timbers so treated can not be 

 subsequently painted, which is desirable 

 in such structures. Moreover, the effect 

 of its volatilization on young plants has 

 never as yet been determined. Other pre- 

 servatives, however, such as mercuric 

 chlorid and zinc chlorid, are better 

 adapted to the purpose, because they leave 

 the surface of the wood in a suitable 

 condition for painting. Both of these 

 have the disadvantage of leaching out 

 to some extent in the course of time. 

 This can probably be largely overcome, 

 however, by proper methods of handling. 

 Of the two, mercuric chlorid is the less 

 soluble and has better antiseptic qual- 

 ities, but is unfortunately more expen- 

 sive. 



Becords show that as far back as 1832 

 John H. Kyan successfully treated the 

 timbers in the Duke of Devonshire's con- 

 servatories by simply soaking them in a 

 mercuric chlorid solution. By this meth- 

 od the solution merely penetrated the 

 wood to a distance of about one-fourth 

 of an inch. By the open-tank method, as 

 suggested, a complete penetration of some 

 species can undoubtedly be secured and 

 there appears to be no good reason, 

 therefore, why such treatment will not 

 lead to better results than have been at- 

 tained in the past with this preserva- 

 tive. 



Object of Experiments. 



Although the preservation of other 



timbers is comparatively well under- 

 stood in this country now, having been 

 carried on successfully for half a cen- 

 tury, the treatment of greenhouse timbers 

 has been neglected. In order, therefore, 

 to secure data which will be of value 

 to the users of such material, the Forest 

 Service of the U. S. Department of Agri- 

 culture is preparing to carry on a series 

 of experiments in co-operation with S. 

 Jacobs & Sons, m^Lnufacturers of green- 

 houses and horticultural buildings, at 

 their plant in Brooklyn. The object of 

 the experiments is to learn: 



1. . What preservative is best adapted 

 to the treatment of greenhouse timbers. 



2. The minimum strength of the so- 

 lution necessary to effectively guard 

 against decay. 



3. The possibility of treating cheaper 

 grades of lumber so that they will last 

 as long or longer than those at present 

 used. 



The preservatives to be used in the ex- 

 periments are mercuric chlorid (corrosive 

 sublimate), zinc chlorid, and probably 

 creosote. The woods to be treated are 

 sap cypress, longleaf and shortleaf pine. 

 Cottonwood will probably be added later. 

 The treating apparatus will consist of 

 two tanks about 18x3x3 feet in size, one 

 for the hot and the other for the cold 

 bath. The heating tank will be made 

 of 14-gauge galvanized iron and will bft 

 heated by about 100 feet of steam coil 

 arranged in the bottom. The cooling 

 tank is to be 2-inch plank and will be 

 used exclusively for the mercuric chlorid 

 solution, which acts on iron and there- 

 fore can not be used in metal tanks. 



The manufactured timbers will be 

 heated in a zinc chlorid solution, as pre- 

 viously described, or else in an improvised 

 dry kiln for several hours and then 

 placed immediately in the cooling tank 

 containing the solution of mercuric 

 chlorid. After the required time in thia 

 bath they will be removed, marked for 



