What is the block effect?
The block effect is attributable to the crystal, which cements the wood slats together. With seasonal changes, indoor humidity in homes ranges from low to high, causing wood fibers to expand and contract. In a favorable situation, small gaps form between each board. In this ideal environment, there is no block effect because the wood can freely express its properties. Thus, following the seasons, wood fibers naturally swell and shrink. Conversely, when using a crystal varnish, it prevents the normal work of the wood. This is because this vitrifying coating becomes inflexible when it dries. It hinders the authentic character of the wood. During the winter season, heating devices reduce the relative humidity in the air, causing the wood slats to tighten. This phenomenon causes the varnish to section. As the crystal is rigid, instead of following the movements of the slats, it sections at its weakest point, thus creating what is called the block effect. As can be seen in the image above, a wide crack is generated every five to six boards. Under optimal conditions, a small gap would occur between each slat. See the image above for an example of the block effect.
