adhesive ex. weldbond
adhesive - used to bond tesserae to a base. ex. thinset, weldbond, silicone.
acrylic additive - can be used with thinset instead of water to increase adhesion & flexibility.
andamento - mosaic detail
andamento - movement or flow of tesserae, often accentuated by the interstices.
annealing - slow glass cooling process starting at around 500°C in a special oven.
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back buttering - spreading adhesive on the back of the tile immediately before applying it to a base.
base - (substrate) the surface that the tesserae are adhered to. ex. wood, metal, glass.
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glass blower making cartellina
cartellina (pl. cartelline) - a thin layer of blown glass (usually as thin as 0.2 to 1 millimetre, but occasionally as thick as 10 millimetres) covering the metal leaf in gold and silver tesserae. The cartellina is applied by firing and protects the metal leaf from oxidation. If the cartellina comes loose, a common phenomenon in ancient mosaics, it leads to the loss of the metal leaf and the tessera is discoloured.
cartoon for mosaic reproduction
cartoon - a full size drawing of the mosaic which can include color and andemento. When creating a reproduction each tesserae is drawn in after taking an exact tracing from the original.
concrete board - A panel made out of concrete and fiberglass usually used as a tile backing material. Recommended for wet or exterior applications.
crazing - the cracking which can occur in glazed tiles or china due to tensile stresses.
cutting - the method used to break up materials into various sizes of tesserae. The hammer and hardie have been used since ancient times and are still one of the preferred methods for smalti & stone. The smalti or stone is placed on the blade of the chisel at right angles and by delivering a sharp blow with the hammer a clean-cut is made. To facilitate cutting glass, the surface may be scored beforehand with a diamond tool. With smalti, since the cut edge reflects more of its brilliance, it is usually placed facing outwards in the mosaic (except in the case of metal-leaf tesserae). Modern tools for cutting include tile nippers, tile cutters, wet saws & glass cutters.
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direct method - the design is sketched onto a base and the tesserae are adhered directly onto it. When complete, a layer of grout can be spread over the tiles then wiped off, filling any spaces between the tiles. The only drawback to this method is that repositioning tiles is difficult after the adhesive has set. (usually involves a chisel)
double reverse method - mosaic lime bed detail
double reverse method - "the ravenna method" reverse cartoon tracing is transferred onto a lime bed and tesserae are placed directly into the lime. When mosaic is complete cheesecloth is glued to the mosaic with a water-soluable glue, traditionally rabbit skin glue. When dry the mosaic is lifted out of the lime, the back is cleaned and then adhered to a final substrate. This method allows a great amount of flexibility, changes are easily made.
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epoxy - a strong two part adhesive consisting of a resin & hardener, great for heavier pieces.
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filati - (thread) rods of smalti that are melted and drawn out extremely thin, then clipped or cut into tiny pieces. Used in micro mosaics.
frost proof tile - tile manufactured for use where freezing and thawing conditions occur. ex. unglazed or porcelain tile.
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glass cutter - simple inexpensive tool that consists of a small hard metal wheel set into a brass bearing with a handle. It can cut straight and curved lines.
glass grinder - used to grind the sharp edges of glass.
gold leaf - a thin sheet obtained by beating gold (20 grams yields around 1 cubic millimetre or 6 square metres).
gold leaf tesserae (mosaic gold) - 24k gold-leaf tesserae are made up of a glass support layer (usually transparent, at times opaque red or coloured) less than one centimetre thick. The 24k gold metal leaf is then sandwiched between the support and a thin protective glass layer (the cartellina). In tesserae the colour shade is determined by the purity of the metal, the thickness of the leaf, the colour, if any, of the cartellina and of the support.
grout - a type of chemically setting cement that fills the interstices between the tesserae. Grout produces hard, dense joints that are resistant to shrinking, cracking and wear.
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hammer - italian "martellina" - mosaic tool used with a hardie to cut tesserae since ancient times.
hardie - used with a hammer the hardie has a chiseled edge and is traditionally mounted in a log.
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tesserae face down image after flipping
indirect method - adhere tesserae face down on a temporary surface (craft paper) with a temporary glue. When complete apply mortar to the mosaic (back buttering) then flip it onto the final surface, also prepared with mortar. Press the mosaic firmly into the adhesive to get a firm bond, level and when set, remove paper with water. Corrections are easier to make using this method but there are a few drawbacks; the tiles may shift in the process and you must be able to envision the mirror image of the design. You work looking at the back of the tiles, (which are not always the same as the front) therefore you don't really see the upside of the mosaic until you flip it. Very difficult especially for figures as in the example above of Lilian Broca's "Queen Esther". copyright © 2006 Lilian Broca
interstice - no grout - marble mosaic detail
interstice - space separating the tesserae which can play an integral part in the final design of the mosaic. see joint.
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joint - grouted - stained glass mosaic detail
joint - space between tesserae, generally filled with mortar, plaster or grout. The joint unifies the mosaic and if grouted the color choice becomes a strong design element. see interstice
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keying - scoring or roughing up the substrate surface to better accept the adhesive.
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lime putty - hydrated lime - (air-setting not hydraulic) must be kept moist by spraying the surface with water and covering with plastic when not working. Can stay soft and workable for months. Used in double reverse method.
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mastic - premixed ceramic tile adhesive. Not recommended for exterior applications.
medium density fibreboard
medium density fibreboard - MDF is a type of hardboard, which is made from wood fibres glued under heat and pressure. Suitable for indoor applications where moisture is not a factor, seal both faces and edges.
micromosaic - mosaic made of tiny tesserae (at times less than one millimetre long) obtained from thin rods of uniformly cut polychrome glass paste or filati.
millefiori - italian "mille" (thousand) "fiori" (flower) - decorative glass made by cutting and arranging cross sections of fused glass rods of various colors and thicknesses.
mortar - a type of cement made from a mixture of cement and fine sand. see thinset
morton portable glass shop
morton portable glass shop - makes repetitive cuts fast and accurate. Cuts triangles, rectangles, diamonds (any geometric shape) easily. Just measure one time, then cut two or a hundred pieces.
mosaic - reproduction
mosaic - the decoration of a surface with small juxtaposed fragments (tesserae) of glass, enamel, stone, or ceramic arranged according to a design traced on a specially prepared base.
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opus - a creative piece of work in any field of the arts. In mosaic art, opus refers to the technique of positioning the tesserae.
opus certum - mosaic where all tesserae are cut and laid uniformly.
opus circumactum - mosaic detail
opus circumactum - a technique for laying tesserae in fan-like patterns, usually used as a background. Creates movement.
opus classicum - mosaic detail - "cave canem"
opus classicum - a combination of opus tessellatum (background) and opus vermiculatum surrounding the main object. This technique creates a very strong, sharp and clear image. ex. Cave Canem, Pompeii. National Museum, Naples.
opus incertum - mosaic detail
opus incertum - mosaic using small smoothed stone tesserae cut irregularly and positioned randomly.
"hunting a lion" - opus lapilla - mosaic detail
opus lapilli - mosaic consisting of small pebbles of many natural colors, one of the first types of paving. ex. Hunting a lion – pebble floor, 4th century BC, Pella (Macedonia) Pella Museum.
opus musivum -"cupid picking grapes" - mosaic detail
opus musivum - "work of the muses" originally referred to glass paste mosaic work on walls or vaults. Today it is recognized when the opus vermiculatum is extended out so that the entire area is filled becoming opus musivum.. This gives the piece a dynamic sense of movement. ex. "cupid picking grapes" - 4th C. AD mosaic fragment, Carthage, Tunisia
opus palladanium -mosaic detail
opus palladanium - a random placement of irregularly cut mosaic tesserae, referred to as crazy paving. It is important to keep the interstices consistant, this method can create a dynamic background quickly and easily. A modern technique.
opus regulatum - mosaic detail
opus regulatum - mosaic laid in a regular grid-like pattern, as you would get a sheet of mosaic tiles from the factory. Used to fill in large backgrounds, very static.
opus reticulatum - mosaic detail
opus reticulatum - mosaic similiar to opus tesselatum but with the tesserae laid out according to oblique lines.
opus scutulata pavimenta - mosaic detail
opus scutulata pavimenta - similar to opus signinum, made of clay powder and lime but with the random insertion of sections of marble or stone of various types, size, shapes and colors. These pieces are then tamped down & leveled. Numerous in Pompei, Herculaneum & Rome.
opus sectile - mosaic detail - "tiger assaulting a calf"
opus sectile - the tesserae are of various sizes but cut very carefully to form exact shapes, the shapes then fit together like a puzzle. Similiar to marble marquetry. ex. tiger assaulting a calf - coloured marbles - second quarter of 4th century AD Rome, Esquiline - Basilica Iunii Bassi
opus signinum - mosaic detail
opus signinum - an ancient form of paving based on layers of mortar made from clay powder and lime (cocciopesto). Black or white cubic tesserae were inserted in the surface forming simple geometrical patterns.
opus tesselatum - mosaic detail - baths of Herculanum
opus tesselatum - latin " set with small cubes" - small tesserae cubes laid in a rectilinear pattern. This technique was used for geometric designs, borders and backgrounds. Often in brick pattern. ex. baths of Herculanum - mosaic detail
opus vemiculatum - mosaic detail - tunisia
opus vermiculatum - latin "worm-like"- this method is used to highlight the contours of the main images. The tesserae create a halo effect which also emphasizes movement.
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pique assiette - ( a french term -"stolen from plate") pieces of broken pottery, china, glass, buttons, figurines, and/ jewelry are cemented onto a base to create a new surface. Almost any form can be used as a base, and any combination of pieces can be applied, restricted only by the individual creator's imagination.
pistol grip glass cutter
pistol grip glass cutter - glass cutter with a comfortable grip.
pizza - a thin smalti slab or disc which is made by pressing the fused glass on a flat surface or by drawing it through two cylinders. After annealing, the slab is cut with diamond-pointed instruments or a hammer and hardie.
porcelain tile - a tile generally made by the dust-pressed method of a composition that produces a dense impervious fine-grained tile. Perfect for exterior applications.
pot life - the period of time during which a material maintains its workable properties after it has been mixed.
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rabbit skin glue
rabbit skin glue - This glue comes in pellets because it is very strong and is water-soluable. The glue is boiled and has a nasty smell but is still used in Ravenna for the double reverse method.
rigid wrap - a plaster impregnated gauze that can be used to add stability to objects otherwise not solid enough to mosaic. It is also used for casting objects.
rotti - irregular sized smalti pieces and bull nosed edge cuts from the smalti pizza.
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shelf life - maximum interval during which a material may be stored and remain in a usable condition.
silicone sealant - an adhesive that is waterproof and remains flexible, will adhere two non porous materials together such as glass on glass applications.
smalti slabs or pizzas
slab - a thin smalti slab or disc (pizza) which is made by pressing the fused glass on a flat surface or by drawing it through two cylinders. After annealing, the slab is cut with diamond-pointed instruments or a hammer and hardie.
slake - a chemical reaction that takes place after the water or admix is mixed to the thinset or grout. It is important to let this reaction take place by not disturbing the mix for approx. 10 minutes after initially mixing.
smalto (pl. smalti) - smalti is characterized by its dazzling range of brilliant opaque colors. Smalti is prepared by adding crystalline material (corpo) and coloured material (anima) to the colourless or coloured fused glass. Smalti is literally available in thousands of colors, is a very stable glass, easy to cut and very durable.
substrate - (base) the surface that the tesserae are adhered to. ex. wood, metal, glass.
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tesserae - small, usually square pieces of glass or other material used to make a mosaic. Their size generally ranges from a few millimetres to two centimetres long and five to ten millimetres thick. The term derives from the Greek word meaning "four-sided".
thinset - a mortar based setting adhesive that is mixed with either water or an acrylic additive, applied approximately 1/8" thick. Great for exterior applications or areas exposed to water.
tile cutter - a device used to break tiles using a method of scoring and snapping.
tile nippers - special pliers that are used to nip or cut tesserae.
two wheeled mosaic cutter
two wheeled mosaic cutter - a hand tool for cutting mosaic tesserae, great for glass
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vitreous tile - square glass mosaic tiles most commonly 3/4" x 3/4" made in molds from glass paste. They have a smooth top but the bottom is keyed with ridges for better adhesion.
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wedi board - a strong light weight cement board ideal for larger mosaics. The core is made from Styrofoam brand polystyrene foam and is reinforced with glass fiber fabric before being coated with polymer-modified cement mortar.
wet saw - a saw with a circular diamond blade that cuts through dense materials incuding marbles and granites.