However, this technique sets limits for the width and length of the planks. It also requires using even grain and boughless material, which is relatively expensive. Grain around the burls is much more dense than along the timber and the denser the wood, the longer it will burn. Thus, when using a stack method of charring boughed material, the result is uneven and the burning process uncontrollable! Due to the movement of heat from the bottom up, a hot air whirl will arise and it will give more heat to the center part of the plank while the corners will get less heat. As a result the plank will be hollow at the center.
Another common way to char the surface of the wood is to do it with a burner, which is much more time consuming, but with the wood available for us it ensures a more consistent and controlled outcome. However, this technology allows to char surfaces with different profiles, which the stack method does not.
To obtain an orderly charred surface the experts practical work experience is particularly important! The relief of charring is a matter of taste, but if you want to carbonize the surface to protect the wood the recommended charred coat is 3mm minimum!