Mosaic is the art of creating images with an assembly of small pieces known as tesserae.

The word ‘tessera’ comes from the number ‘four’ in Greek, because it has 4 sides.

Mosaic is a technique for decorative art, for interior decoration, or for cultural and spiritual significance like in a cathedral.

Small pieces of stone or glass of different colors, normally roughly cubic, known as tesserae, (diminutive tessellae), are used to create a pattern or picture.

The tesserae of ancient mosaics were colored pieces of glass or stone.

In some antique pieces  ‘sandwiches’ made with glass and gold (or silver) were also used.

Everything has four sides or is square… there is an exception, though, mother-of-pearl, that is typically used as circles.

In the modern mosaics, any material can be used to assemble the image: ceramic, resin, wood, metal.

The evolution of contemporary mosaic art brought some artists to use any sort of materials, even sugar cubes, corks, etc.

The tesserae are individual units that, placed next to the others, create lines to create images or textures. They can therefore create an individual style characterizing an artist or sometimes even the signature of the artist who made it.

Use of interstices as part of mosaic

Interstices between the tesserae may be a part of the mosaic too. They also make the difference between a mosaic and a painting.

Ancient mosaicists used to paint the interstices, that unfortunately changed color quickly because of dust and dirt. Today we can not see how beautiful they would have been originally.

The inclination of tesserae is important because the light reflecting differently creates different vibrations and emotions depending on the observation point.

There are tesserae that reflect light like glass and metal, and others that absorb light like marble or stone.

The ancient mosaicists used both together. For example, to make the shadow of a gold portion, they used yellow or brown stones, in order to absorbe the light reflection.

Some materials tend to degrade quickly (e.g. some types of marble)

However, there are products that preserve them, keeping the particles from falling apart.

Here are the main reasons that cause tesserae detachment:

Human reasons: vandalism, accidents, wars, etc.

Natural events: floods, earthquakes, water infiltration, climate conditions.

The repairing process depends on the event that caused the damage.

In Europe the restoration of ancient masterpieces is regulated by law.