HARDWOOD RECORD 



37 



MATERIALS AND METHODS USED 



Experiments and tests were made with a number of cliemicals to 

 determine whether they might be applied to lumber in a way to 

 render it immune from attacks of fungus between cutting time 

 at the mill and the time when the wood had sufficiently air 

 seasoned in the yard to place it out of danger. This period usually 

 covers from thirty to sixty days. The chemicals employed were of 

 three classes: 



Class one contained deliquescent salts, such as calcium chloride 

 and magnesium chloride, the purpose being to keep the boards in a 

 thoroughly saturated condition. 



Class two included borax, sodium carbonate, sodium bicarbonate, 

 lime, and sodium hydroxide. These were selected to neutralize any 

 acid substances that might be present in or formed by the wood. 



Class three contained chemicals that were expected to poison the 

 fungi, and included zinc and mercuric chlorides, copper sulphate, 

 phenol and naphthalene flakes. All of these except the last were 

 mixed in a wooden trough at atmospheric temperature. No arti- 

 ficial heat was used except in a borax solution, when water was 

 warmed to a temperature of about 114 degrees F. Naphthalene 

 flakes were simply sprinkled between freshly cut boards. 



The apparatus employed was a wooden trough in which a solution 

 was placed. The immersion of the boards in the fluid was done by 

 hand. They were held in this solution less than a minute and then 

 stacked in the yard, half in solid piles, to put the preservative to a 

 most severe test, and half in open piles, according to ordinary mill 

 methods. 



RESULTS OF EXPERIMENTS 

 All untreated boards placed in soUd piles were stained in less than 

 one month. Those piled openly were not so severely, attacked, but 

 only thirty-five per cent of them remained bright at the end of one 

 month 's exposure. 



The experiments with calcium and magnesium chlorides were not 

 successful. Solid piled boards in this treatment were practically all 

 heavily stained. 



A five per cent of borax solution was used. Boards treated with 

 it in both open and close piles were attacked, and all the boards 

 in the close piles and seventy-five per cent of those in the open 

 piles were stained within two weeks. After one month 's exposure 

 ninety-two per cent of the boards in the open piles were stained. 

 The boards treated with it are frequently covered with a streaky 

 white precipitate. 



The employment of a four per cent sodium carbonate and a two 

 per cent unslaked lime was experimented with. At the end of two 

 weeks seventy-six per cent of the closely piled boards were dis- 

 colored, while all in the open piles remained clear. At the end of 

 another two weeks most of the boards in the open piles showed 

 stain, and the experiment was discontinued. This solution left 

 streaky white precipitates on the surface of the wood. 



Boards dipped in a three per cent solution of sodium hydroxide 

 and placed in close piles were practically all stained at the end of 

 thirty days. A five per cent solution was then used, and the boards 

 placed in both open and close piles. At the end of a month ninety- 

 eight per cent of the boards in close piles and about seventy per 

 cent in the open piles had been attacked. The boards were stained 

 a vivid yellow. However, the color became less pronounced on long 

 exposure. 



Solutions of sodium bicarbonate of from five to fifteen per cent 

 in concentration were used. At the end of a month seventeen per 

 cent of the boards treated with the five per cent solution and exposed 

 in an open pile, and ninety-seven per cent in a close pile, were 

 stained. With an eight per cent solution and an exposure of thirty 

 days only, twenty per cent of the boards in the open pile were dis- 

 colored, but in the close pile eighty-seven per cent were affected. 

 When a twelve per cent solution was employed all boards in the open 

 pile remained bright at the end of a month, but seventy per cent 

 of those in the close pUe were stained. Boards treated with a fifteen 

 per cent preparation and placed in open piles were free from the 

 stain at the end of thirty days. Practically all o^ those in the solid 

 pile were attacked. 



These results show that the solution of sodium bicarbonate was 

 better than any of the other alkalis used. The heavier concentra- 

 tions w'ere effective when the boards were placed in open piles, but 

 were not effective when they were close piled. The treated wood 

 was stained yellow, but the color partly disappeared in time. Sodium 

 bicarbonate has a tendency to leave a streaky precipitate on the 

 surface of the boards. 



If the lumber is planed before shipment the objection on account 

 of precipitates is removed, but a number of manufacturers contend 

 that in the planing of lumber their machine knives are quickly 

 dulled. However, tests made at the Forest Products laboratory indi- 

 cated no marked tendency on the part of soda-dipped boards to 

 increase the dulling of knives. It appears that careless dipping 

 increases the knives' dulling. 



A phenol or carbolic acid test was made with a two per cent solu- 

 tion of this chemical. This test was not successful. An experi- 

 ment also was made with sprinkling the boards with naphthalene 

 flakes. The test proved impractical. 



A .5 to 5 per cent solution of copper sulphate was also used. 

 The lighter solution proved wholly ineffective, and after a month's 

 exposure, seventy-seven per cent of the boards in the open pile and 

 all of those in the close pile were stained. This solution discolored 

 the lumber with vivid green streaks, and the experiment was 

 abandoned. 



Experimental tests were made with one to five per cent solutions 

 of zinc chloride, which did not prove to be a panacea. 



Further experiments w'ere made with mercuric chloride, ranging 

 from one per cent to less in strength. Eighty-six per cent of the 

 boards treated with the lighter strength solution were attacked by 

 stain, but the .1 per cent solution was more effective. All boards 

 treated with it and placed in open piles were clear at the end of 

 forty-two days, while only fourteen per cent of those in close piles 

 had been attacked. Two months after treatment only four per cent 

 in the open pile were stained, but ninety-three per cent in the close 

 pile showed discoloration. With a .2 per cent solution only one 

 per cent of the open pile boards were stained at the end of two 

 months. In the close pUe, however, eighty-five per cent were attacked. 

 As far as effectiveness in preventing stain is concerned, mercuric 

 chloride solutions gave the best results. Moreover, there was no 

 precipitation on or discoloration of the boards, but on account of 

 their poisonous nature, and their activity in corroding metal brought 

 into contact with them, such solutions are not commended. 



INSECT ATTACKS 



Some depreciation in the value of lumber used in the experimental 

 work was caused by the attacks of wood-boring insects. During 

 the progress of the experiments observations were made to deter- 

 mine what effect the different methods of stacking had on the activi- 

 ties of the insects. It was found that in the open piles practically 

 no insect damage occurred, but in close piles the sap-wood was fre- 

 quently bored into, especially where bark adhered to it. Such attacks 

 were not noticeable in wood treated with deliquescent salts, which 

 had a tendency to keep the surface moist. It appears, therefore, that 

 rapid drying lessens insect damage. No insect attacks were noticed 

 where boards had been treated with mercuric chloride solutions. 



HARDNESS AND STRENGTH 



Tests showed that the soda-dipped wood is slightly stronger, stiffer 

 and tougher than untreated wood, but the difference is so small that 

 it may be due to inherent differences in the wood. It is safe to 

 conclude that these properties are not reduced by treatment with the 

 sodium bicarbonate. The soda-dipped short leaf pine showed a 

 slight increase in surface hardness, which disappeared after the 

 wood became thoroughly air dry. Tests on the long-leaf pine showed 

 that the treatment made the surface harder. If any increased hard- 

 ness appeared at first it disappeared within three months. 



INFLAMMABILITY OF SODA-DIPPED WOOD 



It is claimed that shavings from soda-dipped wood can not be 

 readily burned, and tests were made at the Madison laboratory to 

 procure reliable data on the subject. Shavings treated with bicar- 



