Glossary of terms: Micromosaic Art, Micro Mosaics, Antiques and Furniture for Collectors.

Welcome to our Micro Mosaic (Micromosaic) and Pietra Dura, Art History and Art Collecting Glossary. Here you will find the commonly used terms of the art history profession.

ADHESIVE: Relative to mosaics, the substance used to hold the mosaic in its frame or backing. A substance containing linseed oil is used which allows the adhesive to dry slowly, allowing the artist more time to place his tesserae.

EN GRISAILLE: A French term in art used to describe a picture or depiction in monochrome or shades of gray, often in imitation of sculpture.

LEVIGATURA: The process of polishing the surface of the mosaic to make it smooth and uniform. Wax is used to fill in the spaces between the tesserae. Sometimes the wax is colored to match the surrounding tesserae. The mosaic is then polished several times with progressively finer grades of pulverized sandstone, and finally with a pad of lead or emery. After washing and drying, a final smooth coat of wax is added to protect the surface.

GLASS MOSAIC: Mosaic made of glass, such as those at St. Mark’s, Venice. Unlike smalti, glass mosaic are brittle and reflective.

MICROMOSAIC: A term coined by Arthur Gilbert to refer to Roman mosaics with the smallest tesserae, sometimes as many as 1,500-5,000 per quare inch.

MOSAIC: A decorative object or architectural element made from relatively uniformly sized pieces of hard substances fitted together and embedded in a matrix of some adhesive or bonding substance that eventually hardens to hold the pieces in place. The word derives from the Greek word for the Muses, implying it is a form of artistic expression.

The substance made at the Vatican Mosaic Studio for use in the mosaics of St. Peter’s Basilica, and later for other pictorial and decorative objects. It was used as early as 1600, and gradually improved and increased in variety to over 28,000 different shades. It was made into cakes which were hammered or broken into cube-like pieces called tesserae.

PLASTER: Before a mosaic is begun, a layer of plaster was put on the backing support, and the outlines of the picture were drawn on it. The plaster was removed bit by bit as it was replaced with a layer of adhesive and then the tesserae.

ROMAN MOSAIC

Can refer to ancient Roman mosaics, but here refers to the opaque enamel mosaics made in Rome as distinguished from glass mosaics like those at St. Mark’s (Venice), or hardstone mosaics made in Florence.

SMALTI FILATI: Filati means “thread” in Italian. Smalti filati literally means thread tesserae. The opaque enamel is heated and pulled out to make long thin strands shaped similar to spaghetti or linguini. These are then broken into shorter pieces called tesserae. These originated about mid 18th century at the Vatican Mosaic Workshops.

SMALTI: Flat rectilinear tesserae made by pouring molten opaque colored enamel onto a steel slab, allowing it to cool, and then cutting it into small flat or cubed pieces called tesserae. The smalti are composed of silica, an alkaline substance such as soda or potash, lead, metal oxide coloring agents, and tin oxide for opacity. Opaque tesserae were desirable to avoid a shiny reflective surface when using mosaics as copies of paintings in St. Peter’s Basilica. Smalti means “enamels”(smalto means enamel) in Italian, but used in English as a singular term, enamel. We say micromosaics are made of enamel, not “enamels.”.

SUPPORT: The supportive backing for the mosaic, its material depending on the size of the art work. In small pieces such as jewelry, the backing was made of a metal such as a copper tray with a rim, or of glass, goldstone, or small plaques of marble, which were hollowed out to the proper depth to hold the mosaic. For larger scale pictures, the weight necessitated use of slate or marble, similarly hollowed out, or iron surrounded by a rim.

TESSERA (Plural: Tesserae): From the Greek for “four sided,” the term is said to have first ben used by Pliny when referring to pavements made of such cubes. The pieces which make up a mosaic, usually a hard inorganic material such as marble, stone, opaque enamel, glass or other mineral substance, natural or man-made.

The letters R.F.S. P. Or R.F.S.P.V. sometimes found on mosaics refers to the Studio del Musaico dell Reverenda Fabbrica di S. Pietro (the Mosaic Studio of the Reverend Work yard or Work shop of St. Peter’s). It was first started around 1576 to create architectural mosaics for the new basilica, and was later established as a distinct entity in 1727.