Journal of Surface Engineered Materials and Advanced Technology, 2013, 3, 49-54 doi:10.4236/jsemat.2013.31A007 Published Online February 2013 (http://www.scirp.org/journal/jsemat) 49 Advances in Probing Wood-Coating Interface by Microscopy: A Review Adya P. Singh 1* , Byung-Dae Park 1 , Arif Nuryawan 1 , Menda Kazayawoko 2 1 Department of Wood Science and Technology, Kyungpook National University, Daegu, South Korea; 2 Departement de Gestion des Ressources Naturelles, Faculte des Sciences Agronomiques, Universite de Kinshasa, Kinshasa, Democratic Republic of the Congo. Email: * adyasingh@hotmail.com Received December 18 th , 2012; revised January 20 th , 2013; accepted January 28 th , 2013 ABSTRACT Surface coatings provide protection to wood products against weathering and other deteriorating factors, such as mois- ture uptake and microbial invasion. The effectiveness of coatings depends on many factors, including how well the ap- plied coatings adhere to the wood surface. Coating adhesion to wood involves both chemical and physical interactions between the coating and wood tissues in contact, and the particular focus of this mini-review will be on the advances being made in understanding the physical aspects of the interaction by probing wood-coating interface using novel and high resolution imaging techniques, including confocal laser scanning microscopy (CLSM), SEM-backscattered elec- tron imaging and correlative microscopy employing light, confocal and scanning electron microscopy. Keywords: Wood-Coating Interface; Coating Adhesion; Correlative Microscopy; Backscattered Electron Imaging; Confocal Laser Scanning Microscopy 1. Introduction Wood products exposed in service under outdoor condi- tions can deteriorate from the damaging effects of solar radiation, which can cause weathering of cell walls [1- 10], and cell wall degradation by microorganisms [11,12]. Application of suitable coatings to the product surface can significantly extend the service life by preventing solar radiation from reaching the wood surface and or- ganisms and moisture to come in direct contact with the underlying wood tissues. Among the factors that influ- ence coating performance coating adhesion to wood is of major importance [13], which primarily depends on coat- ing penetration into wood [14] and mechanical anchorage through entanglement of coatings within penetrated sur- face and subsurface layers of wood tissues [15,16]. Ex- amining wood-coating interface is therefore important to understand the nature of wood-coating interaction, in- formation that can be helpful in evaluating adhesion and performance of applied coatings and ultimately in opti- mizing formulations and processes to achieve high dura- bility of wood-coating composites. Microscopy has been the most widely applied tool to examine and image wood-coating interface. Whereas the majority microscopic studies have aimed to record in- formation on depth to which the applied coatings can penetrate into wood products made from different wood types as well as those variously surfaced [14,17-24], specialized microscopic techniques have also been de- veloped and employed that can resolve wood-coating interface more clearly, providing improved understand- ing of wood-coating interaction at cellular and sub- cellular levels [15,16,25]. In this mini-review the focus will be on these technical advances in probing wood- coating interface, often involving a combination of dif- ferent types of microscopes that differ in their imaging capabilities and can provide complementary information. The information presented is in a broader context to in- clude places of physical contact of coatings with the sur- faces of wood products to which they are applied as well as all contact interfaces between penetrated coatings and cell walls around cell lumens and lining cell wall cracks within tissue layers underneath the surface. 2. Novel Microscopic Approaches for Imaging Wood-Coating Interface The importance of coating adhesion for coating durabil- ity and performance has been recognized for a long time. Among the factors that influence coating adhesion to wood surface, coating penetration into and entanglement within surface and subsurface tissues are important, as improvements in water repellency result in greater di- mensional stability and less cracking of wood in outdoor exposures, aspects that have been emphasized in several * Corresponding author. Copyright © 2013 SciRes. JSEMAT