This article describes the research and subsequent treatment to flatten the warped wooden doors of a seventeenth-century cabinet. The aim was to flatten the veneered panels, in very strict climatic conditions and without lifting any veneer or damaging the surface finish of the exterior. In this research, the bending strength and modulus of elasticity of oak, at different temperatures and moisture contents perpendicular to the grain, were determined by experiment. Based on a literature survey, the maximum amount of moisture and heat which was safe to apply was determined. This enabled us to straighten the veneered panels in a very controlled manner.