Similarly when works of art are packed under a modified atmosphere, the permeability of the used packaging material used should be considered. In the present study with materials that were not consuming oxygen or significantly emitting gases, a high barrier material which has a very low permeability with respect to all gases was deemed to be suitable in order to keep a constant protective atmosphere within the packaging as long as possible. Changes in the composition of the modified atmosphere are however inevitable. Due to the presence of the modified atmosphere, a gradient in the concentration of one or several gases is created between the atmosphere at the interior and the exterior of the packed work of art. Thisgradient is the driving force of a spontaneous natural phenomenon,which tends to neutralise the gradient and thus restore the atmo-sphere inside the packed work. One can only slow down this natural process by using the above mentioned high barrier materials and avoid leakages.