THE EFECT OF WOOD STRUCTURE IN THE QUALITY OF FINISHING

The subject of "Gluing and finishing of wood" is part of the teaching program of Bachelor level. The improvement of the subject structure leads on increasing the ratio of practice hours over the theory hours. For this purpose, students participated in two projects, one regarding the properties of finishing and the other regarding the properties of the gluing. In the first project, students investigated how the wood surface properties affect the performance of finishing. Wood species, thus its anatomy, is the primary factor that determines surface properties of wood. A study is carry out in the Laboratory of Wood Study in Forest Science Faculty to determine the quality of coat by observing the result obtained by the finishing process of seven different wood species such as fir, pine, beech, oak, and walnut. There are prepared 5 samples for each specie and the same polyurethane lacquer is applied. After a very careful observation it resulted that It was easy to finish and to get a good quality of coat for fir as a representative of "no transition" or gradual-transition, and for beech as the representative of diffuse-porous hardwoods. It was moderately easy to finish and to get a good quality of coat for walnut as a representative of semi-ring-porous hardwoods. It was difficult to finish and to get a good quality of coat for Pine as the representative of abrupt-transition softwoods, and for oak as the representative of ring-porous hardwoods. After the project, the students can clearly understood how to improve the quality of finishing the different kind of wood. The results of the project had a great impact on practice.