Glossary

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This glossary was derived from various sources and represents generally accepted usage of terms in the forest products industry.

grain In its restrictive meaning, grain designates the direction of alignment of wood elements that determines a plane of cleavage. This term is also used in a variety of ways to describe the size, arrangement, appearance, or other qualities of wood fibers. (See also cross grain, curly grain , diagonal grain, edge grain, fine grain, flat grain , interlocked grain, open grain, spiral grain, straight grain, texture, figure.)

grain raising The objectionable roughness of wood caused by the swelling and stiffening of the short, broken fibres on the surface.

grain raising green Used in referring to freshly sawn or undried wood. Wood that has become completely wet after immersion in water is not considered green but may be said to be in the `green condition.'

growth-ring figure See figure.

gum A comprehensive term for nonvolatile, viscous plant exudates which either dissolve or swell in contact with water. Many substances referred to as gums, such as pine and spruce gum, are actually oleoresins.

gymnosperm A term signifying plants bearing exposed seeds, usually borne in cones. See also softwoods.

gypsumboard A panel material formed of gypsum plaster faced on both sides by a sheet of structural paper.

hardboard A generic term for a panel manufactured primarily from interfelted lignocellulosic fibers (usually wood), consolidated under heat and pressure in a hot press to a density of 497 kg/m3 (31 lb/cu ft) or greater.

hardwoods Generally one of the botanical groups of trees that have broad leaves in contrast to the conifers or softwoods. The wood produced by these trees contains pores. The term has no reference to the actual hardness of the wood.

headrig The first machine in a sawmill to start the breakdown of logs into lumber products.

headsaw The principal saw in a sawmill used for the breakdown of logs by cutting parallel to the grain.

heart check A radial shake originating from the heart or central portion of a log. Also called `heart shake' and `rift crack.'

heart shake See heart check.

heartwood The inner core of a woody stem, where the cells no longer participate in the life processes of the tree. Usually contains extractive materials that give it a darker color and greater decay resistance than the outer enveloping layer (sapwood).

hemicellulose Noncellulosic polysaccharides of the cell wall that are easily decomposed by dilute acid, yielding several different simple sugars.

high temperature drying In kiln drying wood, use of dry-bulb temperatures of 212 degrees F. or more.

holocellulose The total carbohydrate fraction of wood - that is, cellulose plus hemicellulose.

honeycombing A term used to describe advanced white rot; also checks, often not visible on the surface, that occur in the interior of a piece of wood, usually along the wood rays during seasoning.

hot press A major piece of plywood plant equipment which, through heat and pressure bonds the assembled veneer plies and adhesive into a panel.

humidification The process of adding moisture to the finished board.

humidity, absolute The weight of water vapor per unit volume of space.

humidity, relative Ratio of the amount of water vapor present in the air to that which the air would hold at saturation at the same temperature. It is usually considered on the basis of the weight of the vapor, but for accuracy it should be considered on the basis of vapor pressures.

hydrogenation Treatment of wood with hydrogen and suitable catalysts at high temperature and pressure to produce a gas or oils.

hydrolysis Conversion of the polysaccharides in wood or other cellulosic materials into sugars by treatment (hydrolysis) of wood with acids.

hygrometer An instrument for measuring relative humidity, often consisting of dry-bulb and wet-bulb thermometers.

hygroscopic A descriptive adjective applied to materials that readily absorb and retain moisture from the atmosphere.

hyphae Threadlike strands of fungi.

intergrown knot See knots.

interlocked grain A cross grain condition in which the direction of slope of the fibers alternates periodically between left-hand and right-hand spiral arrangements.

isocyanate adhesives Based on polymethylene polyphenyl isocyanate and methylene bisphenyl diisocyanate (MDI).

isotropic Having identical properties in all directions.

ISO 9000 A series of internationally recognized quality system standards that specify the requirements of a quality system, not it's product or service.