Mosaic: From Clay Cones to Gaudí's Broken Tiles, and How to Color It

Long before anyone numbered a coloring page, people were making pictures out of separate pieces of color. That is the whole idea of mosaic, and it is close to the idea behind color by number: a picture built from many small areas, each holding one flat color.

The word comes, through Italian and Latin, from a Greek word meaning "belonging to the Muses", in other words artistic. Each piece in a mosaic is called a tessera, plural tesserae.

Clay cones and river pebbles

One of the oldest relatives of mosaic comes from Uruk, a city in what is now Iraq, more than five thousand years ago. Builders there drove small colored cones of stone and clay into temple walls and columns, so that their round ends formed geometric patterns across the surface.

Later, the Greeks paved floors with natural pebbles chosen for their color. Pebble floors go back to the Bronze Age, and by the 4th century BC they had become real pictures. A famous example is the Stag Hunt Mosaic from Pella, the capital of ancient Macedonia.

Roman tesserae

The Romans cut stone and glass into small, roughly square cubes, and mosaic floors spread through houses and villas from Britain to Syria. There were two main techniques. In opus tessellatum, larger cubes were laid on site. In opus vermiculatum, tiny tesserae, often 4 millimeters or less, followed the outlines of shapes so closely that the result could imitate painting. Fine panels like these, called emblemata, were often set into the middle of a coarser floor.

Byzantine gold

In the Byzantine world, mosaic climbed from the floor to the walls and domes. Church interiors were generally covered with mosaics of colored glass, and backgrounds of gold tesserae made whole vaults shine. Ravenna in Italy became a major center in the 5th and 6th centuries, and its Basilica of San Vitale still shows the emperor Justinian and his court in glass and gold.

Islamic glass and tile

Early Islamic builders carried the craft on. The Dome of the Rock in Jerusalem, completed in the late 7th century, was decorated with glass mosaics by craftsmen of the Byzantine tradition, and the courtyard of the Great Mosque of Damascus shows trees, flowers and small towns with no human figures. Centuries later, workshops in North Africa and al-Andalus perfected zellij: glazed tiles chipped by hand into small shapes and fitted together like a puzzle into geometric patterns. The Alhambra in Granada is a famous example, and zellij is still made in Morocco today.

Gaudí's broken tiles

In early 20th-century Barcelona, the architect Antoni Gaudí and his collaborator Josep Maria Jujol revived trencadís, mosaic made from shards of broken tile and china. Gaudí's buildings curve in every direction and flat tiles would not lie on them, so the tiles were broken into irregular pieces. Park Güell, built between 1900 and 1914, is the best-known example.

Why mosaic suits color by number

A mosaic maker and someone coloring by number do similar work. Both put one flat color into one bounded piece, again and again, and trust that the pieces will add up. A single piece means little on its own, yet a few dozen together suddenly read as a pattern or a picture. Even the thin outlines between areas play the part of the gaps between tesserae.

How daubday's mosaic pictures are made

The Mosaic theme does not copy any historical mosaic. Each picture is generated from a seed:

1. Between 18 and 63 points are scattered across the square.
2. Every spot belongs to its nearest point, which divides the square into irregular, straight-edged tiles.
3. Each tile gets one of up to eight colors at random.
4. A large circle in another color is placed in the middle, covering the tiles beneath it. It spans anywhere from about a quarter to nearly half the width of the picture.

So these pictures are closer to trencadís, or to the irregular pieces mosaicists call opus palladianum ("crazy paving"), than to neat rows of cubes. One detail surprises people: when neighboring tiles get the same color, they merge into one area with no line between them. A bent or unusually long shape is often two or three tiles joined together, and it takes a single tap. Most mosaic pictures end up with somewhere between a dozen and about fifty-five areas and six to nine colors, so the gallery labels them Easy or Medium.

Tips for coloring mosaics

• Start with the circle. It is one area, so a single tap gives the picture its center. In most pictures no tile uses its number, though sometimes a tile of a similar color shares it.
• Go color by color. Tiles of one color are scattered all over, so pick a color and follow the light gray-blue tint across the whole picture.
• Trust merged shapes. If an odd shape shows one number, it is one area, however many tiles it seems to contain.
• Check the circle's edge. Where the circle cuts across tiles it can leave thin slivers. Near the end, Hint will lead you to whatever is left.
• Drag on a touch screen. When you are zoomed in, a drag that starts on an area of the selected color paints the matching areas it passes and leaves other colors alone. The small areas guide explains more.

For another tradition of pieces fitted edge to edge, read about jogakbo, the Korean patchwork wrapping cloth.