The full size drawing on which the finished mosaic is based. It is usually worked out on strong brown paper in complete detail and in full color, ready to be transferred to the permanent mounting surface by means of pouncing or by going over the outline with a stylus. When making copies of ancient mosaics, each tessera is marked and colored on the cartoon so that the mosaic is an exact replica, tesserae by tesserae.
CEMENT/ADHESIVE/BINDER
A substance used to bind particles together providing mechanical strength and solidity. Produced by loss or absorption of moisture by chemical reactions. Today, common binders are limes, cements, natural and synthetic resins.
CERAMIC MOSAIC TILE
Commercially made ceramic tiles used in a hard wear resistant acid proof environment usually on floors. Ceramic tile is usually made in 2cm x 2cm sizes, which are either glued face down on sheets and then mounted using the indirect method or stuck to perforated paper sheets and applied using the direct method. The range of colors is limited and lacks the natural brilliance of stone and smalti.
CUTTING
A procedure where smalto pizza and stone is cut into tesserae of various sizes. Since ancient times, the hardie and hammer have been used and have produced the most accurate, satisfying results. In this method, a piece of material is held against the hardie at right angles in the position of a desired fracture and then struck by the opposing hammer with a single, light touch which will create a clear fracture without splintering. Accurate cutting is essential to exploit the qualities of color and reflection in smalti. In ancient times, apprentices would hone their chopping and cutting skills over many years. Today, other tools are also employed such as nippers and chopping machines. It is important to keep the cutting tools sharp.
GOLD SMALTI
Gold smalti is not uniformly gold. Gold smalti is made of a thin layer of gold sandwiched between two layers of glass. It is very expensive, about 5-6 times the price of colored glass smalti. The traditional method, which is used by MDM, requires pouring a thin layer of glass, applying gold leaf, and then pouring a second layer of glass. Cheaper techniques have been devised, such as placing gold leaf between 2 sheets of plate glass and heating the sandwich, but the adhesion is less secure, resulting in more likelihood of delamination.
GROUT
A fluid mixture usually of lime or cement, fine sand, marble dust and water and is used to fill in the spaces or interstices between the tesserae of a mosaic.
HARDIE
A tool used with mosaic hammer that has a cutting edge like a stonemasons chisel fixed into the center of an upturned heavy log.
INTERSTICES/JOINT
The spaces between tesserae, which can vary in width and could be filled with grout. In Byzantine times a wide spacing was considered a part of the overall effect, while the solidity of floor mosaics always depended on a close fitting texture.
LIME PUTTY
A white putty-like mixture made by mixing 56 parts lime to 54 parts water or by adding the required amount of water to hydrated lime. Used today in mosaic making as a temporary setting binder in the double reverse method of mosaic making.
MARBLE
A metamorphic rock, mainly comprised of calcium carbonate and crystalline in structure originated from limestone and altered by heat or metamorphic pressure. It has been widely used in decoration and is easily worked into shaped into tesserae. It comes in a wide range of color depending on the minerals present such as pink, brown, green, black, yellow, brown and white… which is pure calcium carbonate.
MONOCHROME MOSAIC
Roman floor mosaic made with black and white tesserae from 1st century BC to 3rd century AD.
MOSAIC
Mosaic is the art of decorating a surface with designs made up of closely set, small pieces of material such as colored stone, glass or other ceramic. Mosaic pieces are called tesserae. This technique is principally used to decorate walls, floors and vaults. In Byzantine times, a portable mosaic was a small size depicting a single icon or figure such as the saints, and today portable mosaics of any topic still constitute the most common form of mosaic and are of canvas-sized dimension or less.
PIZZA/PANCAKE
Round discs of glass 1-2 cm thick and 15-30 cm diameter, are made by pressing molten glass paste. After cooling, the discs of glass are cut into strips about 2 cm wide and cut into pieces of smalti, often with a chopping machine.
SMALTI/SMALTO
Smalti refers to the genuine opaque colored vitreous glass from which tesserae are obtained for mosaics. Smalti is ordinary glass with metal oxides added as coloring agents and produces an opaque and fleshy effect. Smalti are unique as a mosaic material and in addition to being weather resistant they offer incomparable reflective power and iridescent brilliance. The color variations are practically unlimited and number over 25,000 and vary according to the type of metal oxides used and the melting temperature.
STONE
General term used to describe those natural materials like rock, marble and minerals used to make mosaic tesserae
TESSERAE
Mosaic pieces called tesserae (from the Latin word meaning dice or cubes), applied to a prepared surface with an adhesive such as plaster, cement or mortar.
VITREOUS MOSAIC/VITREOUS GLASS TILE/GLASS MOSAIC
Mosaic glass that is commercially manufactured using glass paste similar to that of genuine smalti, but limited in color range to about 80 colors versus the 25,000 or more smalti colors. Usually cut into uniform squares of 4-5 cm each and glued on sheets 30 cm square which are removed and pressed into the permanent binder.