The consequences of stress developed between wood and its surface coating Wood is generally considered the sinner when the surface coating flakes off as a result of a change of relative humidity. The situation is, however, complicated by the great dimensional stability and stiffness of wood in the axial direction, along the length of the fibres. Chinese lacquer is applied at high RH, to speed the hardening of the resin.
Stress develops in the lacquer layer.
It is relieved, or even reversed, by the shrinkage of the underlying wood as it also dries out. The lines of the cracks have been emphasised in this close-up. Notice that the cracks change orientation on the curved part. The pattern reveals the construction of the box. The cracks are always across the grain.