Analytical study of Delftware's reproductions

• Published in: Microchemical journal 2020-06, Vol.155, p.104677, Article 104677
• Main Author: Wouters, Helena J.M.
• Format: Article
• Language: English
• Subjects: Authenticity; Ceramics; Delftware; Non-destructive analysis; Tin glaze; XRF
• ISSN: 0026-265X; 1095-9149
• DOI: 10.1016/j.microc.2020.104677

•For the 20th century productions made in Desvres by Martel evidence was found that they differ from original 17th and 18th century Delftware by a missing Coperta Layer.•The white tin-glaze of the 20th century contains no copper, but instead zinc is always present and can sometimes be extremely high.•Purified or synthetic soda and purified sand has been used to make the 20th century glass frit, the masticot.•The 20th century blue glaze is made of a different cobalt source compared to authentic Delftware, since it has no arsenic and bismuth as impurity and the characteristic elements as iron and nickel are different in occurrence. The famous Dutch Delftware was often reproduced in an expert manner, so that based on only connoisseurship it is difficult to come to definitive conclusions about the provenance of tin-glaze objects even for museums with major collections. Amongst others, the French faïencerie Géo Martel was known as one of the largest manufactories of “à la façon de” Delft faience during the early 20th century. In parallel to the analytical research of the white tin-glaze and blue on-glaze decoration of historic Delftware executed at the Rijksmuseum, Amsterdam, a chemical investigation of Géo Martel's reproductions was set up at the KIK-IRPA glass lab. The study aims to reveal significant chemical markers to authenticate Dutch Delftware. Non-destructive EDXRF analysis was performed at around 40 artefacts, a part belonging to the “Musée de la Céramique”, Desvres, France and another part selected from the collected items after the closing down of Géo Martel's Manufactory. The results obtained for the Martel's reproductions illustrate that compared to original 17th and 18th century Delft, for almost all objects the Coperta layer was missing, the tin-glaze contains no trace of copper but instead zinc was always present and can sometimes be in a high amount, the use of purified or synthetic soda and purified sand has been revealed and in the blue glaze arsenic and bismuth as trace elements of the cobalt colour are always absent and the contribution of iron and nickel was different.