Composition, microstructure and corrosion mechanisms of Catalan Modernist enamelled glass

The materials, painting techniques and conservation state of the enamelled stain glass of the Catalan Modernist workshops operating in Barcelona are studied. It is known for its creativity and artistic value where textured, flashed, coloured and enamelled glasses concur. In the late 19th century, Catalan workshops used a new type of ready-to-be-used enamels (lead-zinc borosilicate glass) incorporating pigment particles and colourants. Although humidity, pollutants and solar irradiation are the main causes of corrosion, the microstructure of the enamels plays a role- Enamels that contain large particles close to the surface appear more corroded than those that are fully amorphous. Lixiviation of lead, boron and zinc produced a hydrated layered silica rich fragile glass and the subsequent precipitation of lead, sodium and calcium compounds on the surface, cracks around particles and inside the bubbles decrease the chemical and mechanical stability. The practices of some workshops produced enamels with reduced stability.