Radiata Pine Clearwood Properties
Radiata pine is recognised internationally as being suitable for a wide range of uses; due to its favourable sawing, drying, treatment, and machining characteristics. Other reasons include its ease of finishing, and attractive texture and appearance.
One of its unique properties is its uniform density, i.e. the small variation in density between spring wood and summer wood within a growth ring. It is this property which provides radiata pine with its excellent machining, painting and staining properties.
Consisting mainly of white sapwood, with prominent fine resin canals, it presents a uniform appearance with little colour variation between pieces. This is an advantage for subsequent finishing.
Machining and finishing
Comprehensive tests undertaken have shown that radiata pine has machining properties (cross-cutting, turning, planing, moulding, boring, sanding) equal to, or superior to, many of the internationally traded softwoods. Its fast growth does not adversely affect its working properties and good results can be obtained with all types of hand and machine tools.
The full range of interior and exterior stains, oils, varnishes and paints may be used on radiata pine. The absence of high concentrations of extractives prevents any incompatibility with finishes and eliminates the need for special primers. A very high standard of finishing can be obtained. The wood can be stained to resemble a wide range of traditional timber species.
Being of medium density and even texture and having a good resistance to splitting, radiata pine can be nailed particularly well. The same properties allow the production of efficient joints using other systems, e.g. screws and proprietary connections.
Low extractives content and uniform density allow achievement of above-average glued connections e.g. dowels and finger-joints. The high strength of glued dowel joints is due to the contribution from the end grain to the joint.
Dimensional stability is a crucial wood property for interior fittings and joinery uses. Radiata pine has a low shrinkage which contributes to its stability. However, stability is also affected by a number of other properties, including: equilibrium moisture content, straightness of grain, spiral grain, rate of moisture uptake, permeability to liquids and gases.
Long term movement is the property which best describes the dimension changes which occur when joinery is exposed to dry summer conditions and later to wet winter conditions. The dimensional response of cladding and joinery when exposed to fluctuating weather conditions, such as alternating rain wetting and sunshine, is best described as short-term movement.
Because of the presence of spiral grain, the juvenile wood of radiata pine should not be used where stability is vital to performance. Dimensional performance can be increased by use of finger-jointing, and/or lamination.
Radiata pine must be preservative-treated for exterior uses. However, it is one of the most permeable wood species and can, therefore, be acceptably treated by pressure impregnation, double vacuum and simple immersion methods. LOSP treatments are very successful for joinery.
Preservative treatment to the strict hazard-class specifications allow the New Zealand industry to give service life guarantees for external use products.