A note on face veneer checking in maple plywood

Abstract

A common challenge related to hardwood plywood is checking along the grain of face veneers. This study tested the hypothesis that face checking of rotary peeled maple veneer plywood will be greater on the loose side of the veneer and that checking will be reduced by the application of a clear film-forming finish. Fifteen panels were constructed with the tight side of the face veneer oriented out (i.e. exposed to the atmosphere) and 15 with the loose side of the face veneer oriented out. Half of each panel was finished with lacquer and the other half left unfinished. Panels were conditioned in a hot, wet chamber, visually inspected, and then inspected again after conditioning in a hot, dry chamber. Contrary to conventional wisdom, panels oriented with the tight side of the face veneer oriented out checked significantly more than panels with the loose side oriented out. There was no effect due to finishing. Because these findings are contrary to established practices, further investigation is warranted.

An optical method for rapid examination of check development in decorative plywood panels

“…Using manual/visual methods, capturing the peak check development for every specimen in a large collection of panels is extremely challenging if at all possible. Some checks may even close prior to being counted and/or measured (Holcombe 1952;Cassens and Leng 2003;Leavengood et al 2011). Historically, these limitations have adversely impacted the number of factors such as core type, veneer thickness, adhesive, etc., that could be considered in any individual study.…”

“…The definitions and metrics used in previous studies focus on check count and reflect the fundamental difficulties of commonly used measurement methods relying on manual handling and visual inspection of panels (Batey 1955;Cassens and Leng 2003;Leavengood et al 2011). Batey (1955 proposed a method in which panels were inspected with an unaided eye through a square grid of horizontal and vertical lines spaced 2.54 cm apart on the test specimen.…”

“…The mechanism of development of drying stresses and checking has been extensively researched in the context of commercial drying of sawn lumber (Felix and Morlier 1992;Mårtensson and Svensson 1997;Ormarsson et al 1999;Svensson and Martensson 2002). The principal cause of checking in hardwood plywood face veneers is variable shrinkage rates and moisture content differences between the drying face veneer and the moist core material of the product (Gilmore and Hanover 1990;Forbes 1997;Schramm 2003;Cassens and Leng 2003;Christiansen and Knaebe 2004;Leavengood et al 2011). Checks occur when the tension stresses in the drying face veneer exceed the ultimate tensile strength perpendicular to the grain.…”

“…In these groups the average amount of checking was heavily influenced by the panels with little to no checking, while the panel with uncharacteristically high CDs were outliers within their groups. Outliers such as these make summarizing checking amongst groups of panels subject to possible misinterpretation, but may help to explain apparent contradictions in previous research such as the effect of lathe-check orientation on check formation (c.f., Cassens and Leng 2003;Leavengood et al 2011), and the challenges manufacturers have in addressing complaints related to checking.…”

Investigating face veneer check development in decorative plywood panels: the impact of four common manufacturing factors

“…In uses where appearance is most critical, any defect in the face veneer can lead to complaints by the customer. For many years a common and costly customer complaint has been checking in the face veneer (Holcombe 1952;Cassens et al 2003;Leavengood et al 2011). No standard stipulates the minimum wood-tissue separation to qualify as a check, and no study has assessed end-user views on acceptable levels of checking in finished panel products.…”