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FIGURE 1.-Brown sap stain in western yellow or Pondosa pine lumber. This is a chocolate-colored stain caused by a fungus developing in the wood cells. It is usually found at the ends of boards since it enters the ends of logs and develops inward

Some types of kiln burn resemble closely the two stains previously described, but the color is more nearly uniform than in kiln brown stain. Wood showing kiln burn also is usually more easily dented than wood having any of the other brown stains.

Machine burn is a familiar type of brown discoloration found in finished stock. The scorched or burned areas develop when the progress of the piece through the machine is retarded and heat is generated by friction.

Water stain is a yellowish to dark-brownish surface stain on lumber. It is very common on the lighter colored woods upon which water has dripped or collected during seasoning or storage. It usually planes off readily.

DISTINCTION BETWEEN STAINS

The lumberman often finds it difficult to differentiate between stains produced by chemical action and some of those produced by fungi. For convenience, the term "brown stain" will be used to designate both kiln brown stain and yard brown stain, since their outward appearances are so similar. Kiln burn and machine burn are usually sufficiently different to be distinctive.

TABLE 1.-Differences in gross characters between brown chemical stains and brown sap stain, which is caused by a fungus

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White margin near ends and edges of boards and near juncture of heart and sapwood:

Deepest color is next to white margin.

In western yellow, jack, and Norway pines, rays often show deeper color (flecked).... Stain penetrates throughout sapwood..

Stain often superficial or just below surface.

Color appears in stored logs...

Color appears during seasoning or storage of lumber.

1 Indicates presence of characters or stain, and o indicates absence of characters or stain. Ridgway. Color standards and color nomenclature.

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The gross characters of these defects are tabulated in Table 1 and show considerable differences between brown stain and brown sap stain. The brown stains are commonly found in sapwood but also occur in heartwood and may extend throughout the length of the stock. The defect varies considerably, rarely shows flecking, is often superficial or just beneath the surface, and invariably shows a white margin near ends, edges, and surfaces of boards and near juncture of heartwood and sapwood. The discoloration always appears in lumber during seasoning or storage. Often confused with

these brown stains is a serious blemish known as brown sap stain (fig. 1), which occurs in the sapwood of western yellow and Norway pine, and less commonly in the white pines, as a rich brown to deep chocolate-brown discoloration. Many graders have been accustomed to look upon it as a stage of decay and to grade accordingly. As a matter of fact, this particular stain is caused by a fungus which acts similarly to the blue-stain fungus and frequently develops side by side with it (fig. 2). The dark uniform color penetrating deeply into the sapwood and the numerous darker flecks appearing in the region of the medullary rays aid in identifying this stain.

Brown sap stain is found exclusively in sapwood, where it extends from the ends of logs or boards. The color is a rich brown, shows a flecking in some woods, penetrates throughout the sapwood in spirelike streaks, and never shows a white margin near edges or ends of boards or in regions bordering the heartwood. The color makes its appearance almost invariably in the logs. Brown sap stain has been observed in various mills throughout Montana, Idaho, Washington, Oregon, California, the Lake States, and in British Columbia. It is primarily a log stain and has not been observed progressing in the lumber of air-seasoning piles. The fungus apparently enters the ends or barked portions of logs held in storage for too long a period during the warmer months. The result is a serious blemish, which is reported to cause considerable loss through degrade. Graders should exercise care in grading stock containing this blemish. Such boards may often be placed one grade higher if graded on the basis that the blemish is merely a sap stain and not a stage of decay. It is obvious that considerably greater losses will result if this sap stain is regarded as an early stage of decay rather than as a blemish resembling blue stain in its action upon wood. This unnecessary degrading of brown sap stain should be avoided.

ECONOMIC IMPORTANCE OF BROWN STAINS

Definite figures of the estimated loss from all types of brown stain are not available, but estimates have been made on the loss due to certain types. The brown stains not due to fungous actionkiln brown stain and yard brown stain-cause serious losses in western yellow pine and sugar pine in California, Oregon, Washington, and Idaho. From these two types the greater loss is in kiln-dried stock.

One mill reports that 35 per cent of its output of sugar pine is affected by brown stain. Another mill reports that out of a carload containing 23.000 board feet of sugar pine 11 per cent are rejected on account of brown stain. Western yellow pine graded as B select and better and selling at $105 per thousand board feet may be reduced in grade by brown stain to either C select at $90 per thousand or to D select at $75 per thousand. The same species graded as No. 3 clear at $70 per thousand may be reduced by this defect to No. 2 shop at $42 per thousand. Similarly, No. 1 shop at $65 per thousand may be reduced to No. 2 shop or to a box grade at $25 per thousand. This indicates that depreciation due to brown stain may amount to as much as $30 per thousand. These prices do not necessarily hold

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FIGURE 2.-Brown sap stain A, and blue stain B, in air-seasoned western yellow or Pondosa pine sapwood from Oregon

at the present time but do indicate the approximate relative values of grades.

Pratt,' in his study on the deterioration of lumber in the California region, shows 21 to 32 per cent of No. 1 and No. 2 shop degraded by brown stain in a total tally of 38,000 board feet.

On the basis of the total 1925 production of western yellow pine and sugar pine in the region where kiln brown stain and yard brown stain are common, an estimate of the degrade due to this defect places the losses at approximately $700,000. (See also work by Pratt.') Estimates have not been made on the losses due to the brownfungus stain, but those from this brown sap stain are higher than they should be, for in many cases this dark stain is classed as decay and for this reason causes greater depreciation than if classed as sap stain on a par with blue stain.

YARD BROWN STAIN

Yard brown stain is the particular type of brown stain which develops during air-seasoning or during storage. (Fig. 3.)

The color resembles closely that of kiln brown stain, but often the color does not show on the surfaces of rough boards, appearing only after planing. When planed the color differs little from that of kiln brown stain and shows the same narrow white margins at the ends and other surfaces of boards and near the juncture of heartwood and sapwood. The presence of the stain just below the surface makes this a troublesome defect in rough lumber, and graders of sugar pine and western yellow pine often scrape the surfaces with the sharp ferrule of the grading stick in order to expose the brown color. Expert graders claim to have a way of recognizing boards which contain this hidden defect. Usually the surface of the board directly over the discolored area shows slightly darker in the region between sapwood and heartwood.

At several mills in California and Oregon it is common practice to pile seasoned sugar pine on lath crossers during long storage in order to avoid "sweating" and brown stain. The "sweating sweating" includes both development of mold and the exudation of sugarlike substances.

Yard brown stain occurs in 1-inch and thicker white pine (P. strobus) stock when air-seasoned or when stored for long periods. (Fig. 3.) This particular stock was observed at a northern Minnesota mill, and most of the brown stain appeared in the heartwood. When delivered to the consumer this stock was mistaken for kilndried material because it was claimed that it showed evidence of having been "burned" in the kiln.

Observations made at various California mills where considerable pine is air-seasoned disclosed only small amounts of yard brown stain in the thinner stock, but more in the stock 6/4-inch and thicker. An interesting observation was made on 6/4-inch air-seasoned western yellow pine. Especially on the upper surfaces and on the edges of this stock in the pile there appeared numerous yellowish gumlike drops, scattered and smaller toward the bark edge and denser and

1 Pratt, M. B., The Deterioration of Lumber: Cal. Ag. Exp. Sta. Bul. 252, pp. 305-307; May, 1915.

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