Pâte-sur-pâte is a French term meaning “paste on paste”. It is a method of porcelain decoration in which a relief design is created on an unfired, unglazed body, usually with a coloured body, by applying successive layers of (usually) white porcelain slip (liquid clay) with a brush. Once the main shape is built up, it is carved away to give fine detail, before the piece is fired. The work is very painstaking and may take weeks of adding extra layers and allowing them to harden before the next is applied. Reference: Wikipedia. It was a popular technique during the Art Nouveau era and many ceramic manufacturers used this technique including makers such as Minton, Doulton and Meissen.
Below are some examples and price guides of Art Nouveau Pâte-sur-pâte items including a Mintons plaque and a Florence Barlow Doulton Lambeth oil lamp.