Visual Features of Araucaria Timber

Araucaria (Hoop Pine) has a reputation as a blond timber. However, colour variations are common. Four of the most significant features of Araucaria are the base timber colour, knots, heartwood stain and kiln stain. These features are assessed using digital image processing.

Timber Colour

Samples of Araucaria timber exhibiting colour variations.

Colour may vary within a timber sample due to grain colouration and other effects. Statistics are used to characterise the colour properties of the timber sample so that colour matching may consider not only the average colour but also the variations within the timber.


Examples of knots in Araucaria timber.

Knots in Araucaria are typically dark brown with a circular structure. However, some knots may be hollow or partially broken.

Heartwood Stain

Cut Araucaria logs displaying heartwood stain.

Heartwood stain in milled timber.

Heartwood stain.

Heartwood stain is a dark colouration which generally occurs in and near the centre of the log. The heartwood stain flows through the timber and typically affects large areas of the milled timber sample, often appearing as wide streaks on the surface. Heartwood stain varies in both intensity and colour.

Kiln Stain

Kiln stain appears as dark colouration in the surface of milled timber.

Kiln stain may develop just below the surface during the drying of Araucaria timber. Kiln stains generally occur at a depth of around three to five millimetres below the surface and only become evident when the timber is dressed. It can be difficult to distinguish between mild cases of kiln stain and naturally occurring grain colouration since the kiln stain may follow the grain of the timber as it does in the example shown here.

Next: Human and Machine Vision Timber Colour Inspection.

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