In Europe, portrait miniatures first appeared in England in the 16th century – painted on stretched parchment or paper. The way of their preparation was inspired by mediaeval illuminated manuscripts. After 1700, ivory plates were introduced and became the most frequent support of the 18th and 19th centuries. Watercolour and gouache were the most common techniques, but there may be other ones. Due to variability in the employed materials, it is not easy to find a uniform analytical procedure.
Since it is not possible to take any samples for materials research – due to the very thin, detailed and highly compact painting – a fully non-invasive multi-analytical approach has been introduced in ALMA. It combines large area scanning techniques (particularly MA-XRF), portable spectroscopic methods, and laboratory methods adopted for measuring small objects in ambient atmospheric conditions (XRPD, environmental SEM). This analytical strategy brought a number of surprising results - copies and forgeries were distinguished, the originality or secondary modification of signatures was proved, retouches and over-paintings were located, highly specific pigments were identified (e.g. Purple of Cassius). For the first time ever, the processes of saponification have been evidenced in miniature portraits.