Page FIGURE15. Tranverse section of box elder cut down in November, 1922, 16. Honeycomb in the "mineral streak areas of kiln-dried maple_ 18. Transverse sections cut from 6/4-inch sap gum boards im- 20. A-Threads of a blue-stain fungus in the wood cells of scrub 21. An old fungous thread (darly shaded) of the blue-stain fungus 23. The yard of a large hardwood plant, showing long piles of stored 26. A simple and inexpensive wooden dip tank, used for experi- 52 27. Cross section of one type of metal dipping tank used in the 56 28. View of the principal parts of a metal dipping tank commonly 58 29. View of the type of steam cylinder used in the pressure steam- 59 30. Trucks loaded with hardwood cooperage billets ready for 33. An example of one of the many ways in which methods of pil- 35. Drawing of a section of Sitka spruce sapwood as seen under the TABLES TABLE 1. Showing differences in gross characters between brown chemical stains and brown sap stain, which is caused by a fungus. - - 2. Relation between sap-stain fungi and moisture content of wood (oven-dry basis), including some wood-rot fungi for comparison. 3. Summary of dipping experiments in the prevention of sap stain ing and molding of wood conducted by various investigators. 50-51 4. Thirty-day antistain-solution test... 57 5. Trial schedules for steam-box treatment (steaming preliminary to air drying) – 65 NATIONAL COMMITTEE ON WOOD UTILIZATION R. P. LAMONT, Chairman. R. Y. STUART, Forester, United States Forest Service, vice chairman. DUDLEY F. HOLTMAN, Construction engineer. EDWARD EYRE HUNT, Secretary. The National Committee on Wood Utilization, established by direction of President Coolidge, comprises about 150 members, representing manufacturers, distributors, and consumers of forest products. Its object is to work for closer utilization of our country's timber resources. The committee, whose headquarters are in the Department of Commerce, Washington, D. C., works in close cooperation with a number of official and private organizations, notably the Bureau of Standards of the Department of Commerce and the Forest Products Laboratory of the Forest Service, Department of Agriculture. FOREWORD Sap stain and decay are among the most important causes of wood waste. These causes may be removed in most instances through proper piling, seasoning, and handling, although in some instances special treating methods may be required. Doctor Hubert, formerly assistant pathologist at the Forest Products Laboratory, has for a number of years given this subject detailed study from a practical as well as a scientific point of view. He has demonstrated his interest by offering this manuscript to the National Committee on Wood Utilization for publication. This bulletin is not only of interest to lumbermen, but also to anyone who uses wood and for whom the prevention of sap stain and decay is an important question. The committee is greatly appreciative of the assistance Doctor Hubert has given on this important phase of wood utilization work. Acknowledgment is also made to the Forest Products Laboratory, John Foley, Dr. Thomas E. Snyder, Phillips A. Hayward, and others who have assisted in reviewing the manuscript. JUNE 15, 1929. AXEL H. OXHOLM, Director. FRONTISPIECE. Photomicrograph showing a hypha of the blue-stain fungus penetrating several tracheid walls in northern white cedar: 1. Radial section stained with safranin. 2. The extreme right-hand portion of 1 enlarged, showing the constricted hyphæ in the bore holes made in the tracheid walls. 3. Photomicrograph showing sporelike development of hyphae of Lasiosphaeria pezizula in persimmon wood; radial section, stained. 4. Enlarged portion of the hypha shown in 1. Note the swelling of the hypha at entrance and emergence and the constriction where passage is secured through the cell wall. 5. Photomicrograph showing hypha of the blue-stain fungus passing through a bordered pit in the wood of loblolly pine. Tangential section stained with safranin and lichtgrün SAP STAINS OF WOOD AND THEIR PREVENTION INTRODUCTION The staining and molding of lumber and other wood products have for many years been serious sources of loss to the lumber industry, which is one of the largest in the country (1926), employing 921,000 wage earners and producing products valued at approximately $4,000,000,000. Aside from their relation to the vital national question of maintaining an adequate timber supply, large losses of this nature can not be suffered by such an important industry without serious efforts being made to prevent them. Research offers the only means of obtaining the information necessary to the development of effective preventive methods, and the first step in this direction is a study of causes and the factors influencing them. Most of the discoloration or stains which lower the quality and value of forest products are caused by certain minute organisms of the lower forms of plant life known as fungi and are very widespread. Another type of stain believed to be due to chemical reactions is not so common but nevertheless causes considerable loss due to degrade. STAINS CHEMICALLY PRODUCED Among the discolorations which apparently result from some chemical changes on the surface or within the wood are several brownish to yellowish stains in both pine and hardwood lumber. The exact nature of the changes is not known. Some of the stains appear in logs stored for a considerable period, while others develop in the lumber during kiln-drying or air-seasoning. The more important of these stains are: STAINS DEFINED Yard brown stain, which occurs as a yellow to dark-brown stain in air-seasoned white pine (Pinus strobus), sugar pine (P. Lambertiana), and western yellow (Pondosa) pine (P. ponderosa). In sugar pine the brown discoloration is often found just below the surface of the sawed boards and therefore is usually undetected until after planing. Kiln brown stain is a yellow to dark-brown discoloration developing during the kiln-drying of sugar pine and western yellow pine. It is a serious factor in the grading of lumber and causes an annual loss that is very appreciable through lowering boards from the more valuable grades. The terms "scorch" and "kiln burn" have often been used to describe these two brown stains. Kiln burn is a very dark browning, scorching, or actual charring of kiln-dried stock, caused by the use of too high temperatures. |