of wood. The value of the slack stock used in the country is nearly 50 per cent more than the value of the tight material. Nearly any wood is suitable for some kind of slack cooperage, but only a few are serviceable for tight.

Woods Used.-"Room exists for considerable choice of wood for staves in slack cooperage, but not so much for containers of liquids. Flour barrels were once made principally of cottonwood staves, but elm has proved to be a good substitute. A white wood that represents a clean appearance is wanted, and it must be tough enough and strong enough to carry the load. It must be free from odor or taste that might injure the contents. The sugar barrel demands material of the same kind.

"Red gum leads all other woods because it is abundant and satisfactory. The shippers of butter, lard, meat and other food products select the most suitable woods for their barrels. Custom has much to do with it, but not all; for it is easy to understand that a pine barrel might taint food with the taste of turpentine. The hardwoods are demanded in three times the number for slack barrels as are the soft-woods; yet many commodities go to market in soft-wood barrels and kegs. Scrub pine is used for nail kegs and for containers of other small hard

ware.

Wide Use of Cooperage Stock. "Extensive use is made of barrels and kegs as shipping containers, and in some places they compete with boxes, while in others they hold the field to themselves. The life of a barrel is put down at one year by the trade, but that is not enough. A majority of barrels are used many times. They begin as sugar or flour barrels, and are then sold to the farmer for shipping his produce to market. It may be said that they are returned to him several times, carrying potatoes to the market on the first trip, and tobacco or lettuce on the next, each cargo being lighter in weight than the previous one, owing to the weakened condition of the barrel. Finally the barrel may serve out its life work as a trash receptacle, and in the end can be used for fuel. Thus it may be said that a barrel fills as useful a career

SIDE DROP TEST FOR BARRELS.

Barrel is dropped on wooden platform covered with steel plate and resting on concrete flooring.

Courtesy of Forest Products Laboratory.

DIAGONAL DROP TEST FOR BARRELS.

The test is identical with the side drop test, except that barrel is dropped on edge.

Employed in testing boxes up to 24" in their greatest dimensions. revolves vertically. Inside of drum contains ridges of wood and metal. each revolution the box tested drops six times.

Machine

With

Courtesy of Forest Products Laboratory.

INTERNAL PRESSURE TEST FOR BARRELS.

Barrel and connecting pipes filled with water to exclude all air. Pressure is then progressively raised until 1 lb. of water escapes from barrel in one minute.

as almost any other manufactured article, and its life is much longer than a season.

"The demand for barrels is constantly growing, because modern machinery has made it possible to make them for the trade cheaper than almost any other form of durable package. That it is the most convenient form of package has long been acknowledged.

"The heaviest demand comes from the cement business, and flour ranks next, closely followed by sugar and salt. As containers for fence staples, bolts, nuts, nails, and packages for roasted coffee, spices, crockery, fruits, and vegetables, they follow in the order named. Glass manufacturers, baking powder companies, liquor distillers, and candy, tobacco, and cheese packers are big users of barrels. The demand for barrels for molasses, oil, lard and pork is also enormous, while dry paint, glue, snuff, oatmeal, screws, castings and general hardware articles annually increase the demand on the cooperage supply.

Characteristics of Woods.-"Some woods are waterproof, others are not. Alcoholic liquors and some oils will pass through the pores of some woods where water will not go. The wood of which a whiskey barrel is made may absorb a gallon of whiskey without any passing through the staves and escaping. Some woods are so porous that barrels made of them will not hold water very long. Coopers learned by experience that certain kinds of wood made better staves than others, when the barrels were intended for liquid. It was wholly a matter of experience at first, but later the microscope helped to explain why some are proof against seepage and others are not. All wood is more or less porous. It is made up of hollow cells, connected one with another by small openings, all microscopic in size; but some of the hardwoods have openings much larger than cells. They are tubes running through the wood, up and down the trunk of the tree, and are called pores or vessels. Some of them, as in oak and ash, are large enough to be seen by the unaided eye, by inspecting the end of a freshly cut

stick. These pores are responsible for the fact that some barrels will not hold liquid. It seeps into the pores and flows along them until it passes entirely through the staves and escapes. That is why wood with large open pores is not suitable for tight barrels.

"White oak has always been considered the best tight cooperage wood. Many years ago it was thought that no other could or should be used for certain liquid commodities, but others have lately come into use. Yet, white oak has large pores, and a casual observer noting that characteristic would conclude that it is not good for tight barrels, but experience shows it to be good. Though it has large pores, which may be easily seen, they are not open. They are closed as a bottle is closed with, a cork, and liquid cannot enter. The plugging substance, which is known as tyloses, is of a whitish color and is deposited in the pores by the wood itself, in the progress of the tree's growth and maturity. It occurs principally after the sapwood has changed into heartwood. Red