TAPPI T 258 PDF

Basic Denisty and Moisture Content of Pulpwood

TAPPI T 258 – Basic Denisty and Moisture Content of Pulpwood

TAPPI T 258 om-16 describes the measurement of the basic density (bone-dry weight per unit of maximum volume) of pulpwood in the form of chips or disks from the cross section of logs. The method also gives procedures for determining the moisture content of wood in either form.

For moisture content of wood in the form of sawdust see TAPPI T 264 “Preparation of Wood for Chemical Analysis (Including Procedures for Removal of Extractives and Determination of Moisture Content).”

Moisture content is determined by the difference in weight as received and after drying at 1053C.

Volume is determined by the amount of water displaced by the test specimen of wood.

Because wood swells or shrinks, respectively, with absorption or loss of water, it is necessary to express the density at a specified moisture content and corresponding volume. The usual conditions are the minimum (oven-dry or moisture-free) weight and the maximum (green) or the minimum (oven-dry or moisture-free) volume. For most purposes, the maximum volume basis is sufficient. In the present method the specimen is considered to have swollen to its maximum volume when its moisture content exceeds the “fiber-saturation point,” which lies between 18 and 26% by weight (wet basis) for most species. Procedures for obtaining the volume, both green and oven-dry, are described in this method.

Many wood technologists consider the density of wood is best expressed only on the basis of oven-dry weight and maximum volume, because at moisture contents above the fiber-saturation point the maximum volume is essentially constant.