The following project reports on an attempt to devise a satisfactory method of cleaning and restoring blackened sulphur-contaminated lead glazed earthenware to its original condition. The material selected for the study came from the French supply ship, the Machault, which sank in the Restigouche River estuary, Quebec, in 1760. Some of the lead glazed earthenware aboard the ship became blackened either because of the fire which destroyed the ship or because of subsequent chemical action in the burial environment. Analysis of the glaze revealed that blackening was due to the formation of lead sulphide in the glaze. A series of experiments was set up based on previous related work with similar problems. Test pieces of pottery were made in the lab to try to reproduce the process of contamination and the formation of black lead sulphide. Most of the experiments centered around refiring the sample in an oxidizing electric kiln at 850°C, with and with-out chemical pre-treatment and intensive washing. Since one of the main problems encountered in refiring was the appearance of a rust coloured stain in the crackalure of the glaze, several experiments were set up to remove excess iron from the sherds by means of various chelating agents. Other tests were aimed at observing the effectiveness of various oxidizing bleaches on the glaze; the use of air abrasive equipment for cleaning; and the use of a partially reducing atmosphere in the kiln. The final experiment tested the effect of refiring at different temperatures sherds which had been cleaned with hydrogen peroxide. It appears that the hydrogen peroxide bleaching followed by re-firing at 850°C is the most effective method of restoring this type of discoloured pottery.