Both clays were calcined by heating at 750°C for 1 hour in air, hot-loaded into a Carbolite 1100 AAF static laboratory furnace. A calcination temperature of 750°C was selected, as no further mass loss due to dehydroxylation was observed above this temperature from either clays' TG curves. A mass of 10 g of clay was loaded in a shallow porcelain crucible.