Pictures on paper framed behind glass are at risk from moisture movement caused by temperature gradients, both transient and seasonal. The temperature gradient can be reduced by mounting pictures about 2 cm from the wall and by preventing direct sunlight from illuminating the picture. Insulation behind the picture provides no benefit. Sealing the back of the frame greatly improves the moisture stability of the enclosure. An absorbent back board within the sealed space stabilizes the picture against changes of ambient relative humidity (RH) but destabilizes the RH at the picture when transient temperature gradients occur.