Expert opinion

Natural and manufacturing defects of plywood

The presence or absence of defects is one of the main criteria for choosing plywood. Basically, natural and manufacturing defects are distinguished.

Low-quality natural raw materials used in the production of this material determine the likelihood of natural defects. Natural defects include knots and shakes. The types of knots include: pin (round or oval with a diameter of up to 5 mm), intergrown, loose or black knots (a more serious defect). A significant defect is the presence of cracks which can be close (tightly pressed together) or open. The next type of natural defect is bark pocket. The light bark pocket is an overgrown bark in the trunk and appears after severe damage to the tree itself. Dark bark pocket is a rather serious defect and it is unacceptable in high-grade plywood. The biggest defect is the formation of rot —   plywood of any grade with such a defect is off-quality.

The manufacturing defects appear as a result of incomplete compliance with the plywood manufacturing technology. Manufacturing defects include hollow imprints and shakes, the appearance of warped and dirty surfaces, glue that has leaked through the veneer layers. Plywood with non-smooth peeling is substandard. Manufacturing defects can be both visible and hidden. Hidden defects can be determined only with the help of special equipment. Visible defects include improper grinding. This defect appears due to improper crimping during grinding, as well as due to different thickness of the sheet in its parts. A defect called rough grinding can appear with poor quality of the sanding belt, insufficient operating pressure during the grinding process. This defect is clearly seen with a naked eye and is quite serious. Provided that the plywood is treated with a worn sanding belt, a "tan" may appear on the sheet of material. Externally, it looks like black spots on plywood sheet. This defect indicates the presence of violations in the structure of the material and is also very serious. Defects that are not seen with a naked eye determine the hidden defect of products. 

For example, plywood may turn out to be defective if low-quality glue was used in production. Despite the fact that externally this material may not have visible defects, such plywood will not be durable. Other violations of production technology have similar consequences, such as insufficient drying of raw materials or non-compliance with the temperature regime during primary glueing. As a result, the plywood may become brickle and begin to delaminate or crumble. Such material can no longer be used during construction work. Due to the poor quality of the product, its scope of application is very limited.

It is necessary to carefully check the plywood for the presence of certain defects to be sure of the choice. The operational characteristics of the finished product, the level of the company's reputation and its competitiveness will depend directly on the result of this process.