These tests indicated that cresol mixed with filled hardened gloss oil and applied to the freshly cut log ends would serve to kill the stain and decay organisms present on the freshly cut surface. It also promised to be effective in preventing the entrance of fungi into the log end after the coating was applied. The waterproofing qualities of hardened gloss oil were already well known and could be depended on to reduce end-checking provided the addition of other ingredients such as cresol did not affect this property. The preliminary tests made by end-coating short bolts of freshly cut box elder FIGURE 26. A simple and inexpensive wooden dip tank used with a mixture of cresol and hardened gloss oil with filler gave very encouraging results. The coated ends developed neither stain nor other discoloring fungi, while the uncoated and control pieces became discolored with moldlike fungi. In an article by Loughborough and Hubert 40 the problem of endcoating of green logs was discussed and certain end-coating mixtures were recommended for trial. Later, Knauss 41 began testing some of these mixtures in freshly cut logs in the southern hardwood region. 40 Loughborough, W. C., and Hubert, E. E., Southern Lumberman 117: 170-174; 1924. 41 Knauss, A. C., Stain Prevention in Gum: Southern Lumberman 120:42; Aug. 22, 42 Following Knauss's work, Teesdale 12 completed the project and published a report. Three mixtures were tested. The first two were suggested by Loughborough and Hubert, while the third was a modification of the second. The following are the formulas, with the proportions given by weight: No. 1. Cresylic acid, 1 part; kerosene, 10 parts. No. 2. Cresylic acid, 1 part; hardened gloss oil, 10 parts. No. 3. Cresylic acid, 1 part; filled hardened gloss oil, 10 parts. The tests indicated that spray treatments of gum logs with formula No. 1 prevented stain and decay but were not effective in preventing end checks. The third formula, however, gave very encouraging results. The untreated logs used as controls in these experiments showed considerable end-checking, and the blue stain and sap rot extended from a few inches to 2 or more feet into the log from the log ends. The cresol-hardened gloss oil with filler is made up as follows: The hardened gloss oil (made up of 8 parts quick lime, 100 parts rosin, 57.5 parts of spirit or solvent) can be obtained from a paint manufacturer, and the barytes, asbestine, and cresol added. The mixture should be thoroughly stirred and when not used should be kept sealed to prevent the loss of cresol by evaporation. The hardened gloss oil and filler serve as an effective waterproof coating, while the cresol is intended to prevent the development of stain and decay. The coating is primarily a log coating but may also be used on the ends of green timbers and plank stock during the period of seasoning. It should also prove of value in coating the ends of green ties and poles before they are piled for storage in order to prevent excessive checking and to reduce stain and decay in these products. The mixture can be applied cold by means of a stiff brush and should be applied forcibly to the moist surfaces, so that it will adhere tightly to the wood as slow drying takes place. If the weather is cold, a slight heating of the mixture will make it easier to apply. The coating should be thick enough so that it will not run before it hardens, and a sufficiently thick layer should be applied to prevent a cracking of the dried mixture and a loss of moisture. The mixture should be applied to the ends and barked sides as soon as practicable after the logs have been cut from the fallen tree. This will necessitate separating the ends of logs, but it is good practice in any event in order to keep blue stain out of the sapwood. The coating prevents the loss of any great amount of water from the log ends and allows a minimum period of time in which stain and decay organisms may become established upon the fresh moist surface. The cresol-hardened gloss oil with filler costs in the neighborhood of 50 to 60 cents per gallon (1926) and required about 1 gallon of the mixture to end-coat 12 logs averaging 2 feet in diameter. 42 Teesdale, L. V., The Control of Stain, Decay, and Other Seasoning Defects in Red Gum: U. S. Dept. of Agri. Dept. Circ. 421: 1–18; 1927. The spraying of logs with various chemical solutions has found favor more particularly in the control of insects which infest logs. The Bureau of Entomology of the United States Department of Agriculture recommends spraying with a variety of chemicals as means of preventing insects from entering green logs. 13 It is a well-known fact that the storage of logs under water is an effective means of preventing losses due to fungi and insects and of avoiding end checks. However, the logs should be completely covered with water, because partial submersion or an alternate wetting and drying will favor the entrance of fungi and insects and will no doubt produce checks. Cases are on record in which fire-killed timber infested with flathead borers was salvage cut and the logs hurried to the log pond in an effort to drown the grubs. The method proved ineffectual, for the grubs abandoned the water-soaked portions of the logs and continued to form their destructive tunnels in the portions of the logs floating above the water level. Stains and decay are unable to develop in well-seasoned and wellcared-for logs, since these contain insufficient moisture. Checks may appear as the result of rapid drying, and certain insects may find the conditions favorable. If sufficiently rapid drying takes place to prevent stain and decay, the practice of decking logs on high skidways may prove beneficial although checks and a certain amount of insect damage may follow. In moist and shady forest areas the logs may be decked in the shade and green brush piled over them, thus reducing evaporation and keeping the logs at a high moisture content unfavorable for fungous development. In extreme cases, where it is found practicable, barking and decking the logs at the proper season may prove effective in preventing all but the damage due to checks. All the methods so far presented, except storage under water, may be used at the same time. In conclusion, it is well to repeat that the best plan is to avoid slow handling or storage if possible. If the log is kept moving from the time it is cut from the tree until it is sawed at the mill there will be a minimum of sap stain and decay, and the damage due to insects and end checks will be greatly reduced. DIPPING IN CHEMICAL SOLUTIONS Earlier experiments with sap-stain preventives have already been mentioned, and a summary of the work, as well as conclusions drawn from a large number of field observations, all seem to point to the fact that we have as yet obtained no perfect dip solution. The sodium carbonate-sodium bicarbonate mixture has so far not been excelled for general dipping practice although under severe weather conditions it also fails to prevent the development of fungi causing discoloration of the sapwood. However, many of these failures may be traced to one or a combination of various factors: 1. Use of too low concentrations of the chemical. 2. Use of cold solutions. The solution should be heated, but the temperature used should be not higher than 160° F., so that breaking down of the chemicals may be avoided. 43 Craighead. F. C. Experiments with Spray Solutions for Preventing Insect Injury to Green Logs: U. S. Dept. of Agri. Bul. 1079: 1-11; August, 1922. 3. Too much dependence upon hydrometer readings when tests for the alkalinity of the solution are required. 4. Delay in getting the green boards into the dip tank. Bulking of green sapwood lumber encourages stain. 5. Delay in moving the dipped stock direct from the dip tank to the air-seasoning piles. 6. Insufficient spacing in the air-seasoning piles resulting in poor air circulation and therefore slow drying of the lumber. 7. Presence of log stain in the lumber before it reaches the dip tank. Surface treatment does not prevent the development of stain in such boards. 8. Careless mixing of solutions. Inaccurate measurements of amounts of chemicals and water. Neither of the two chemicals mentioned used separately or in a 50-50 mixture is a perfect preventive under severe conditions, such as continuous rainy periods during the warmer months, but either will go far toward keeping the stock clean. In rainy seasons an 8 per cent solution of sodium carbonate is desirable. In drier weather a 4 per cent solution is usually sufficient. A high grade of soda ash should contain about 582 per cent alkali, and every effort should be made to conform to this standard of purity. When sodium bicarbonate is used, an 11 per cent solution should be employed in wet weather and 5 to 6 per cent in dry weather. This chemical when dry and pure should contain about 37 per cent alkali. In recent years no conclusive tests have been made in efforts to develop new chemicals for the prevention of sap stains. A preliminary field test made in 1924 showed that a solution made up of 26 pounds of sodium bisulphite and 9 pounds of sodium fluoride in 100 gallons of water was fairly effective in preventing staining and molding of western yellow pine. The solution was used without heating, and produced no discolorations on the dipped boards. The cost of the solution on a 1924 price basis was $1.94 per 100 gallons. For dipping wood products used in the manufacture of food containers a chemical solution which will eventually evaporate, leaving no trace of the chemicals on the seasoned wood, is desirable. Preliminary laboratory tests conducted in 1923 indicate that the following solutions, which are of the above type, merit trial under mill conditions. The cresol-caustic soda dip, costing (1924) $0.48 per 100 gallons, contains 4 pounds of cresol (cresylic acid, 95 per cent) and one-sixth pound of caustic soda in 100 gallons of water. Another solution contains 4 pounds of betanaphthol, 3 pounds of caustic soda, and 1 pound of naphthalene in 100 gallons of water and costs $1.08 per 100 gallons. A pine-oil emulsion made with crude pine oil, soap, and naphthalene is a promising dip, but for the concentrations tested the cost ($3.85 per 100 gallons) was far above the other two solutions. It has the advantage, however, of not discoloring the boards. On the basis of the tests made with the cresol-caustic soda and related dips a patent has been issued to E. Bateman and E. E. Hubert covering the use of this type of sap-stain and mold preventive. (Patent No. 1598699, issued September 7, 1926.) There are other chemical dips which have been employed under semicommercial conditions, the most promising being mercuric chloride (corrosive sublimate) and sodium fluoride. The former gave but has not given completely satisfactory results under severe condiin a 3 per cent solution can be used successfully against blue stain, tions, against molds such as iron its general use is not recommended. Sodium fluoride of its highly poisonous character and its corrosive action upon metals excellent experimental results in a 0.1 per cent solution, but on account FIGURE 27. Cross section of one type of metal dipping tank used in the prevention of sap stain. At A is shown the by-pass for lumber which is not dipped. The drop of the lumber onto the skid C removes much of the adhering sawdust, and thus reduces the amount which accumulates in the bottom of the tank. The drain pan is an economic feature |