*Article* **Shelling of Growth Rings at Softwood Surfaces Exposed to Natural Weathering**

**Lukie H. Leung 1 and Philip D. Evans 1,2,\***


Received: 13 August 2020; Accepted: 2 September 2020; Published: 5 September 2020

**Abstract:** Shelling is the delamination of growth rings and the projection of woody tissue from wood surfaces. Shelling disrupts coatings and makes refinishing difficult, and a better understanding of the phenomenon is needed to help alleviate its unwanted effects. We tested whether confocal profilometry could quantify shelling in flat-faced and profiled-faced western larch deckboards exposed to natural weathering and examined the effects of growth-ring orientation and angle on shelling. Confocal profilometry was able to quantify shelling in both deckboard types. Shelling developed at the surface of flat-faced deckboards oriented pith-side-up, whereas it was absent from boards oriented bark-side-up. We found an inverse correlation between the height of shelled growth rings and the angle of growth rings to the surface of flat-faced boards. Shelling occurred in profiled-faced boards oriented pith-side-up due to the delamination of growth ring tips and projection of latewood from wood surfaces. A superficially similar although less pronounced phenomenon was seen in profiled-faced boards oriented bark-side-up. The shelling of profiled-faced boards oriented pith-side-up created lanceolate-shaped slivers of latewood that projected from the peaks of profiles. Some of these latewood tips were sharp and, for this reason, we sugges<sup>t</sup> that profiled-faced western larch deckboards should always be oriented bark-side-up rather than pith-side-up.

**Keywords:** shelling; western larch; confocal profilometry; profiling; growth rings; latewood; earlywood; pith-side-up; bark-side-up; natural weathering
