The stained glass collection from Palácio da Pena presents a group of Swiss, German and Dutch panels. They exhibit a high quality technique, with the presence of grisaille, silver stain, enamels and sanguine red. The study of the different painting techniques will be made, concerning the production, chemical composition and degradation problems, mainly found in the blue enamels and red sanguine.

Research on historical recipes will be performed, allowing an accurate reproduction of samples of the several painting materials and techniques. Important issues will be approached, such as the evolution of grisaille colours, manufacture of silver stain with tones varying from yellow to red, production of enamels with different colours, red sanguine and also conservation issues concerning these painted surfaces. This work will allow a more accurate approach on stained glass painting techniques, being an important step for the investigation of this artistic discipline. A detailed knowledge of the materials used by the artists is essential to unveil their techniques and to place their works in context as well as to establish the most adequate conservation procedures. Furthermore, most of the current stained glass painting materials do not reflect the older technology and cannot be used as models to study the degradation mechanisms or conservation treatments.

This task will start with the research of treatises on the production of grisaille, silver stain, red sanguine and enamels. Research of the main manuscripts and treatises dated between XII^th and XVIII^th centuries will be held. Some of the main examples are the Schedula Diversarum Artum, by Teophilus, 12th c.; the treatise by Antonio da Pisa, written between the end of the 14th c. and beginning of 15th c.; the Antwerp Manuscript, from the first half of the 16th c.; L’Arte Vetraria, by Antonio Neri, from 1612; Les principes de l’Architecture, by André Felibien, 1676; and the L’Art de la peinture sur verre et de vitrerie by Pierre Le Vieil, 1774.

 After this research, samples according to selected paint recipes will be produced, seeking for chemical and morphological compositions similar to the case studies.

For the grisaille samples, the reproduction will be centred in the preparation of mixtures of iron, lead and copper oxides (in different percentages), with glass powders, in order to obtain different tones, from brown to black.

The preparation of silver stain samples, supported by preliminary studies, will take into account a) glass composition, b) silver stain composition, c) temperature of the kiln and time of exposure. The objective is to reproduce several silver stain shades, from yellow to red.

For the red sanguine, treatises show that it is formed by iron oxide. Samples composed by a mixture of Fe₂O₃, Pb₃O₄ with glass powder will be produced, adding Arabic gum as binding agent. The compositions and morphologies will be studied.

Concerning the production of blue enamels, there are two important aspects to consider: their reproduction and study of their degradation. Studies indicate the preparation of dark blue enamel using saffre or smalt for the colouring substance. Lead and boron oxides can be added as a flux. Finally, recent studies show that some compositions can be unstable and more exposed to degradation, due to the high content of potassium and low content of lead.

Degradation tests will be made in order to assess changes in the morphology and chemical composition of the grisailles, silver stain, blue enamel and red sanguine samples produced. These corrosion experiments will be focused on the effects of moisture and pollutants.

To carry out this task, coordinate by Márcia Vilarigues with the collaboration of Pedro Redol and Joana Delgado and the consultant Stefan Truempler. A BI1 researcher, with training in Conservation Sciences, Chemistry, Physics or Material Sciences will be necessary.