Are glazed ceramics really waterproof? Chemical analysis of the organic residues trapped in some post-medieval glazed slip painted wares found in Florence

Until now nobody has ever done analysis to determine the content of glazed wares because it is always assumed that the glass coating, being waterproof, does not allow the absorption of organic compounds. The goal of this paper is, however, to demonstrate that the presence of imperfections in the coating, due to the use or production faults, allows the absorption of residues in the fabric of the porous ceramic. The data are related to the analysis of the pottery found during the project “Magliabechiana Library” in Florence (Italy).