TECHNICAL NOTE NUMBER 225
V N OF FOREST PATHOLOGY BUREAU OF PLANT INDUSTRY
IN COOPERATION WITH
I STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE
FOREST PRODUCTS LABORATORY
MDSON 5, WISCONSIN _RVI4$ 0,toeK1
CAUSE AND PREVENTION OF BLUJE STA-ININ WQQD
Blue stain is caused by fungi that grow in sa --d-u-- t for
ir food. It is not a stage of decay, although t faro
blue staining also very often lead to infection with decay-producing fungi.
Excepting toughness, blue.stain has little effect on the strength of wood.
To prevent blue stain it is necessary to produce conditions unfavorable to the development of the causal fungi. These fungi are disseminated etr by spores, whichare produced in great abundance and are carried
aut bywind and insects, or by direct growth from infected to uninfected wood. Their growth is dependent upon proper food, moisture, air, and favorable temperatures. If any one of these factors can be rendered
i equate or unfavorable sapwood will not stain.
T wood can be made unsuitable as food for fungi by introducing chemicals into it that are toxic to the fungi. This method of controlling stain in green lumber is used widely. The blue-stain fungi cannot grow in wood which has a moisture content of less than 20 percent nor in wood in which the cell cavities are absolutely full of water. Hence, stain can be prevented either by rapidly drying freshly exposed surfaces to a mois ture content below 20 percent or by keeping the stock submerged in water. Blue-stain fungi grow most rapidly when the temperature is from 75" to 85* F. If the temperature of the wood is below 35* F. or
above 100" F., no stain is likely to take place.
Controlling Blue Stain in Logs
Logs are oftenbadly infected before they are sawed into lumber. Where immediate conversion of logs into lumber or immediate storage of logs in water is impossible, a practicable method of controlling stain is provided by chemical treatment if insect infestations are not severe.
CHEMICAL TREATMENTS: Spraying the ends and barkless areas of freshly cut logs with the following chemicals will substantially retard the occurrence of blue stain in hardwoods during storage periods as long
as 3 months. With the exception of borax, the same treatments are suitable for softwood logs, but they may not give adequate protection for so long a period as with hardwoods.
The antiseptic can be applied with an ordinary garden spray. In warm weather, treatment should not be delayed longer than 24 hours after the trees are felled.
To control end checking as well as stain, any suitable moisture-resistant coating can be applied after the spray treatment.
Insects canbe controlled by thoroughly spraying the logs with a solution containing 0. 5 percent gamma benzene hexachloride in kerosene or light fuel oil.
Solutions for Chemical Treatment of Logs
Product and principal toxic chemical! : Pounds-. per 100 : gallons of water
Dowicide G (sodium pentachlorophenate)4 .... 21
Lignasan (ethyl mercuric phosphate) ..........: 6
Melsan (ethyl mercuric phosphate sodium
pentachlorophenate) ........................ 12
Noxtane (sodium pentachlorophenate
alkaline materials) 30
Permatox 10S (sodium pentachlorophenate plus :
borated materials)........... 30
Santobrite (sodium pentachlorophenate) ........: 21
-Materials are named in alphabetical order. The proprietary products are distributed by the following companies: Dowicide Chapm'an Chemical Co., Memphis, Tenn.
Lignasan) E. I. du Pont de Nemours and Co., Wilmington, Del.
Noxtane Wood Treating Chemicals Co., St. Louis, Mo.
Santobrite Monsanto Chemical Co., St. Louis, Mo., and R. T.
Vanderbilt Co., Inc., New York, N. Y. =The amounts given are the smallest that can safely be used ordinarily.
In localities and seasons in which staining is especially severe the amounts, except for borax, may be advantageously increased by as
much as one-sixth to one-third. Suitable for hardwoods only.
i-The composition of materials designated-by trade names may not always
be the same; therefore past experience with a proprietary product car.
be used as a basis for judging future effects or results only insofar
as its chemical composition remains unchanged.
All the chemicals mentionedare regarded as poisonous. Be sure to read the caution at bottom. of next page before attempting to use them.
Controlling Blue Stain in Lumber and Timbers
The most effect 'ive method of preventing stain in lumbe r is to kiln dry the stock green from the saw. 'By this method moisture conditions are rapidly made unfavorable for the growth of fungi. Stock to be air seasoned can be protected against staining by treating 'the surfaces with chemicals that stop the development of the stain fungi or by employing* special piling methods, such as end racking or crib piling, that 'shorten the time required to diry the surfaces to a moisture content unfavorable for the growth of the fungi. Chemical treatment is cheaper and more effective because it is less dependent on weather conditions ".d, when it is followed by flat piling, the stock dries with ldssa warping and twisting. Chemical treatment 'also is particularly useful for the temporary protection of green timbers.
CHEMICAL TREATMENT of lumber is usually accomplished by dipping, either mechanically or by hand, depending largely on the output of the mill. At some mills the chemical is sprayed on the lumber, but this procedure is most commonly used in treating timbers and dimension items that cannot conveniently be handled in an ordinary dipping vat.
Preparations most commonly employed for use on lumber and timbers are the same as those listed for log treatments. However,, with the exception of borax, the concentrations needed are about one-third those listed in the table for logs. For timbers, the concentrations Irecommended usually are somewhat higher than for lumber. For maximum ef fectiveness and s af ety in handling, directions furni shed by the dietributors should be carefully followed.
For satisfactory results with any dipping or spraying treatment, careful consideration should be given to the following: (1) Stain-free logs. Surface treatment of boards from infected logo will not stop the development 4f fungi already present. (2) Prmttetet Treatment pref erably should not be delayed longer than 24 hours after sawing; delay.
are frequently responsible for interior stain. (3) Thorough coverage of thxe stock. Sufficient attention should be given to the quantity of dipping solution, or the condition of the spray nozzlesB, to insure complete wetting of the surface at all times. (4) Adequate concentration of the chemnical. Solution concentrations should never..be lower than those recommended, but during unfavorable weather they sometime s canbe increased to advantage. (5). Protection of the'treating solution and treated stock from rain. (6) Good seasoning practices .- The treated stock should be piled so that it will dry as rapidly as possible without undue warping or checking. Yard piles. should be as narrow as practical, -properly ele vated, well spaced, and adequately roofed. The use of stock boards as stickers, especially those over 4 inches wide, 'increases. the likelihood of sticker stain., Narrow, dry stickers are greatly to be preferred. Chemically treated stickers last longer than untreated ones and are less likely to carry infection to the lumber.
All of the chemicals mentioned are regarded as poisonous. However, with reasonable care they can be used without known danger. Persons whose skin is found to be particularly sensitive to the chemical being used should avoid it entirely. In any case the chemicals, with the exception of borax, should not be permitted to get on the skin more than neces sary, and not at alluntil they are fully diluted. For hand dipping and handling of the lumber immediately after dipping, waterproof aprons and rubber gloves are advised.
Chemical Treatment of Miscellaneous Wood Products
Antistain chemicals can be applied advantageously to a number of mate rials, other than logs and lumber. Their use can be extended to green posts,, veneer, hoop stock, shingles, lath, and similar products as a means of keeping them bright during seasoning.
PROTECTION OF DRY WOOD: Seasonedwoodagainbecomes susceptible to staining upon wetting; consequently, it must be kept in a reasonably dry condition (Z0O percent moisture content or less) if discoloration is to be avoided. Surface applications of chemicals for stain control during air seasoning provide no permanent protection. Chemical treatmnents are effective for long periods only when they are made to penetrate deeply into the wood, as in properly pressure -treated wood.
UNIVERSITY OF FLORIDA U. S. DEPAP7RUflC:curR
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