Removing insoluble salts from archaeological ceramics. Traditional methods under review

Although insoluble salts are one of the most common alteration forms that archaeological ceramics can present, the methods for their removal have not really changed within the past forty years. Furthermore, not many studies on the topic have been recently published. In this paper, a methodology to study the suitability of different traditional treatments for the removal of these salts, has been established. Ceramic mock-ups made out of a marketed red clay were fired up to 700ºC in laboratory conditions. Their composition and physical properties were studied. A validated method for the growth of calcium carbonate deposits was applied onto them. Afterwards, chemical tests based on three products and three application methods were studied. Finally, the mock-ups’ characteristics were studied again to determine their changes due to the cleaning treatments. Results showed efficacy differences linked to the product and application method. In general, the products applied by immersion and cellulose pulp poultice were more effective than gel treatments, which were less effective with any of the three products tested.