Roman Mosaics - Ancient Art in Tiny Pieces

Once You've Seen One Mosaic, You've Seen Them All - Right?

Roman mosaics are an ancient form of art consisting of geometrical and figural images built up from arrangements of tiny pieces of stone and glass. Thousands of extant fragments and entire mosaics have been found on the walls, ceilings, and floors of Roman ruins scattered throughout the Roman empire.

Some mosaics are made up of small bits of material called tesserae, typically cut cubes of stone or glass of a particular size—in the 3rd century BC, the standard size was between .5-1.5 centimeters (.2-.7 inches) square. Some of the cut stone was specially made to fit the patterns, such as hexagons or irregular shapes to pick out details in the images. Tesserae could also be made of simple stone pebbles, or fragments of specially quarried ​stone, or glass cut from rods or simply broken into fragments. Some artists used colored and opaque glasses or glass paste or faience—some of the truly wealthy classes used gold leaf.

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History of the Mosaic Art

Detail of Mosaic Alexander the Great at the Battle of Issus, Pompeii
Detail of Mosaic Alexander the Great at the Battle of Issus, Pompeii. Getty Images / Leemage/Corbis

Mosaics were part of the decoration and artistic expression of homes, churches, and public places in many locations around the world, not just Rome. The earliest surviving mosaics are from Uruk period in Mesopotamia, pebble-based geometric patterns adhered to massive columns at sites such as Uruk itself. Minoan Greeks made mosaics, and later Greeks as well, incorporating glass by the 2nd century AD.

During the Roman empire, mosaic art became enormously popular: most surviving ancient mosaics are from the first centuries AD and BC. During that period, mosaics commonly appeared in Roman homes, rather than being restricted to special buildings. Mosaics continued in use throughout the later Roman Empire, Byzantine and early Christian periods, and there are even some Islamic period mosaics. In North America, the 14th century Aztecs invented their own mosaic artistry. It's easy to see the fascination: modern gardeners use DIY projects to create their own masterpieces.

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Eastern and Western Mediterranean

Mosaic floor, ruins of the Basilica of Ayia Trias, Famagusta, North Cyprus.
Mosaic floor, ruins of the Basilica of Ayia Trias, Famagusta, North Cyprus, 6th c AD. Peter Thompson/Heritage Images/Getty Images

In the Roman period, there were two main styles of mosaic art, called the Western and the Eastern styles. Both were used in various parts of the Roman Empire, and the extremes of the styles are not necessarily representative of finished products. The western style of mosaic art was more geometric, serving to distinguish functional areas of a house or room. The decorative concept was that of uniformity—a pattern developed in one room or at the threshold would be repeated or echoed in other parts of the house. Many of the western-style walls and floors are simply colored, black and white.

The Eastern notion of mosaics was more elaborate, including many more colors and patterns, often concentrically arranged with decorative frames surrounding central, often figural panels. Some of these remind the modern viewer of oriental rugs. Mosaics at the thresholds of homes decorated in the eastern style were figural and might have only a casual relationship to the main floors of the houses. Some of these reserved finer materials and details for the central portions of a pavement; some of the Eastern motifs used lead strips to enhance the geometric sections.

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Making a Mosaic Floor

Roman-era Mosaic in the Gallo-Roman Museum in Lyon
Roman-era Mosaic in the Gallo-Roman Museum in Lyon. Ken & Nyetta

The best source for information on Roman history and architecture is Vitrivius, who spelled out the steps required to prepare a floor for a mosaic.

  • the site was tested for solidity
  • the surface was prepared by digging, leveled and rammed for stability
  • a rubble layer was spread over the area
  • then a layer of concrete made up of coarse aggregate was placed over that
  • the "rudus" layer was added and rammed to form a layer of 9 digiti thick (~17 cm)
  • the "nucleus" layer was laid, a layer of cement made of powdered brick or tile and lime, not less than 6 digiti thick (11-11.6 cm)

After all that, the workmen embedded the tesserae into the nucleus layer (or perhaps laid a thin layer of lime atop it for that purpose). The tesserae were pressed down into the mortar to set them at a common level and then the surface was ground smooth and polished. The workmen sifted powdered marble on top of the painting, and ​as a final finishing touch laid on a coating of lime and sand to fill in any deeper remaining interstices.

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Mosaic Styles

A mosaic depicting Neptune at the Neptune Baths at Ostia
A mosaic depicting Neptune at the Neptune Baths at Ostia. George Houston (1968) / Institute for the Study of the Ancient World

In his classic text On Architecture, Vitrivius also identified a variety of methods for mosaic construction. An opus signinum was a layer of cement or mortar simply embellished with designs picked out in white marble tesserae. An opus sectile was one that included irregularly shaped blocks, to pick out details in figures. Opus tessalatum was one that relied primarily on uniform cubical tessarae, and opus vermiculatum used a line of tiny (1-4 mm [.1 in]) mosaic tiles to outline a subject or add a shadow.

Colors in mosaics were made up of stones from nearby or far away quarries; some mosaics used exotic imported raw materials. However, once glass was added to the source material, the colors became enormously varied with an added sparkle and vigor. Workmen became alchemists, combining chemical additives from plants and minerals in their recipes to create intense or subtle hues, and to make the glass opaque.

Motifs in mosaics ran from the simple to quite complex geometric designs with repeating patterns of a variety of rosettes, ribbon twist borders, or precise intricate symbols known as guilloche. Figural scenes were often taken from history, such as tales of gods and heroes at battles in Homer's Odyssey. Mythological themes include the sea goddess Thetis, the Three Graces and the Peaceable Kingdom. There were also figural images from Roman daily life: hunting images or sea images, the latter often found in Roman baths. Some were detailed reproductions of paintings, and some, called labyrinth mosaics, were mazes, graphical representations that viewers might trace.

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Craftsmen and Workshops

1st C AD Tigress Attacking A Calf. Mosaic In The Opus Sectile Technique
Tigress Attacking A Calf. Mosaic In The Opus Sectile Technique. Werner Forman / Getty Images / Heritage Images

Vitruvius reports that there were specialists: wall mosaicists (called musivarii) and floor-mosaicists (tessellarii). The primary difference between floor and wall mosaics (besides the obvious) was the use of glass—glass in floor settings was not practical. It is possible that some mosaics, perhaps most, were created on site, but it is also possible that some of the elaborate ones were created in workshops.

Archaeologists have yet to find evidence for the physical locations of workshops where the art might have been assembled. Scholars such as Sheila Campbell suggest that circumstantial evidence exists for guild-based production. Regional similarities in mosaics or a repeated combination of patterns in a standard motif could indicate that mosaics were built by a group of people who shared tasks. However, there are known to have been itinerant workmen who traveled from job to job, and some scholars have suggested that they carried "pattern books," sets of motifs to allow the client to make a selection and still produce a consistent result.

Archaeologists also have yet to discover areas where tesserae themselves were produced. The best chance of that might be associated with glass production: most glass tesserae were either cut from glass rods or were broken off from shaped glass ingots.

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It's a Visual Thing

Mosaic at Delos, Greece (3rd C BC)
Mosaic at Delos, Greece (3rd C BC). Institute for the Study of the Ancient World

Most large floor mosaics are difficult to photograph straight on, and many scholars have resorted to building scaffolds above them to get an objectively rectified image. But scholar Rebecca Molholt (2011) thinks that might be defeating the purpose.

Molholt argues that a floor mosaic needs to be studied from the ground level and in place. The mosaic is part of a greater context, says Molholt, capable of redefining the space it defines--the perspective that you see from the ground is part of that. Any pavement would have been touched or felt by the observer, perhaps even by the bare foot of the visitor.

In particular, Molholt discusses the visual impact of labyrinth or maze mosaics, 56 of which are known from the Roman era. Most of them are from houses, 14 are from Roman baths. Many contain references to the myth of Daedalus's labyrinth, in which Theseus battles the Minotaur at the heart of a maze and thus saves Ariadne. Some have a game-like aspect, with a dizzying view of their abstract designs.

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4th-century mosaic in the vault of a mausoleum built under Constantine the Great for his daughter Constantina (Costanza), who died in 354 AD.
4th-century mosaic in the vault of a mausoleum built under Constantine the Great for his daughter Constantina (Costanza), who died in 354 AD. R Rumora (2012) Institute for the Study of the Ancient World