Samples of a late 18th century mirror are placed in confined spaces in the presence of wood under accelerated ageing conditions. Thirteen different woods are used, each at 100per thousand R.H. and at oven-dry conditions. The mirror samples were placed with the wood to test for contact corrosion and for vapor corrosion. The pH of the woods was measured and the levels of degradation for each mirror sample were compared to the acidic levels of each wood sample. A comparison is made using pH, R.H. and extent of degradation. It is concluded that the acidic level of the wood has little effect on the metallic backings. However, 100per thousand R.H. conditions have a greater effect on the backings and contact corrosion is more severe than vapor corrosion.