Abrasive Water Jet: A tool used to cut intricate curves in hard materials (stone, steel) by way of high pressure water containing an abrasive grit.
Adhesive: Any of a number of fixatives used to bond tesserae to a backing.
Admix: A latex additive to thinset and/or grout to provide a degree of flexibility.
Andamento: Flow or direction. In music, andamento describes the tempo of music, each speed defined and named individually. In mosaic making, andamento can be described by terms such as: movement, flow, circulation, current, course, conveyance, direction, rhythm, or any of their antonyms. Adjectives used to describe andamento may include swirly, wavy, choppy, chunky, scattered, smooth, graceful, strong, and the like. The choice of opera in a mosaic will to a degree determine its andamento.
Antiqued surface: An unpolished but smooth finish with some topography.
Base, Backing: The substrate to which tesserae are adhered.
Backerboard: A cement board used as backing. Commonly for outdoor works or indoor works where water will be present (indoors or outdoors).
Bullnose: Edging treatment. Where a mosaic turns a 90º corner such as along the outside edge of a counter top, a variety of corner treatments may be employed. Bullnosing describes these treatments. Examples include rounded, bevelled, 90 degree, stone, etc.
Buttering, Back Buttering: When using the direct method or when mud setting, adhesive is applied to the backs of individual tesserae prior to placement on backing.
Ceramic Tile: Tile made by firing clay. May be glazed or unglazed. Not suitable for outdoors. Not frost proof. PEI rating: 0 - 3.
Curing: The chemical/mechanical set up of adhesives and grouts. For example, concrete takes 28 days to cure.
Direct Method: A method of mosaic construction where tesserae are placed (adhered) directly onto backing.
Double Hinged Nippers: A double-hinged nipper that provides exceptional leverage.
Dust Mask: A safety device worn to prevent breathing in dust.
Emblema, Emblemata: An insertion, an inlay or a mosaic. Usually referring to a mosaic or portion of a mosaic prepared separately (not direct method) and inserted (Greek/Roman) in a large piece.
Fibreglass Mesh: A mesh made from fibreglass strands. Using the indirect to double indirect methods, the mesh is used to hold a mosaic together from the back. A thin smear of thinset adhesive bonds the mesh to the backs of the tesserae.
Filati: Glass thread used in micro-mosaics.
Float: A rubber, latex, or foam tool used to spread grout into groutlines.
Glazed surface: Glaze is a hard, glass-like coating found on glazed ceramic or glazed porcelain tile surfaces. Glazing closes the surface of the tile, making it impervious to water absorption.
Gold, silver smalti: This smalti is made by sandwiching 24k gold or silver leaf between two sheets of glass. Gold and silver smalti was used extensively by Byzantine mosaic artisans in religious iconography.
Granite: A very hard igneous rock. 6 - 8 on Mohs hardness scale.
Grout: A cementitious filler; placed between tesserae.
Grouting: Working grout into the interstices between tesserae.
Groutline: The interstices between tesserae. The interstices may or may not contain grout.
Grout river: Groutlines that align with neighbouring groutlines form a long line of grout. Grout rivers can be unintentional and distracting or intentional to add elements to a mosaic.
Hardie: Chisel upon which tesserae are fractured.
Hardie Post: A post, usually of milled lumber or a log end, into which a hardie is mounted.
HDF: High density fibreboard. A manufactured board pressed from sawdust and a binding agent. Used as backing (indoors).
Honed surface: Silky smooth, but with a flat non-reflective finish.
Indirect, Reverse Method: A method of mosaic construction where the tesserae of a mosaic are placed upside down on a temporary backing. The finished (upside down) mosaic can then be transported to its final installation location or a permanent backing can be applied to the back of the mosaic and the temporary backing removed.
Interstices: The spaces between tesserae.
Keystoning: Trapezoidal (North American) shaped tesserae. The shaping of keystoned tesserae allows the mosaic artist to maintain parallel edged groutlines perpendicular to a curve. Poorly executed keystoning will result in triangular-shaped interstices. Well executed keystoning will result in parallel edged groutlines.
Limestone: Sedimentary rock composed mainly of calcium carbonate. Often contains fossilised inclusions. 3 - 4 on Mohs hardness scale.
Lozenge: A rhomboid (diamond shaped) design or tessera.
Martelline: Hammer used to fracture stone rods into tesserae. The hammer edge is chisel-like and may be made from steel or employ a carbide insert.
Mastic: A pre-mixed adhesive that uses an acrylic polymer and calcium carbonate.
MDF: Medium density fibreboard. A manufactured board pressed from sawdust and a binding agent. Used as backing (indoors).
Marble: Limestone in metamorphic crystalline or granular state; capable of taking polish, used in sculpture and architecture. Offers natural-looking colour as well as texture. 2.5 - 5 on Mohs hardness scale.
Medium: Term used to describe materials used in mosaic construction. Common media include: stone, ceramics, glass.
Micro-mosaic: Small-scaled mosaics created using short glass threads mounted on end. Thread density may exceed 200 per square centimetre.
Millefiori: The term millefiori originates from the Italian words "mille" (thousand) and "fiori" (flower). Millefiori refers to the pattern of the bead's surface that is the result of a complicated bead-making process. The components of a millefiori bead are murrine (millefiori slices) and a wound glass core, usually of a solid color. The murrine are created with glass rods, or canes, of various colors that are bundled into patterns and fused with heat. They are then reheated, drawn while hot, and sliced. The murrine slices are carefully marvered or pressed onto the molten core of a lampworked bead and fused again.
Mohs Hardness Scale: A scale devised in 1812 by mineralogist Frederick Mohs used to define mineral hardness through scratch resistance.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| talc | gypsum | calcite | fluorite | apatite | feldspar | quartz | topaz | corundum | diamond |
| 2.5 | 2.5 - 3 | 3 | 5.5 | 6.5 | 6 - 7 | 7 - 8 |
| fingernail | gold, silver | copper penny | knife blade | iron pyrite | glass | hardened steel |
Mud Setting: When using the direct method with tesserae of uneven thickness, adhesive is applied to the backs of individual tesserae prior to placement on backing. The amount of adhesive back buttered onto the tesserae is controlled by the mosaic artist to accommodate the thickness differences. Careful mud-setting will result in a flat-surfaced mosaic even with material of dramatically different thickness.
Nibbling: A careful and detailed nipping of media to create a desired shape.
Nipping: The use of nippers to fracture media.
Notched Trowel: Used to spread thinset on backing. Trowels are made with different tooth dimensions and configurations to control the amount of thinset that is spread.
Offset Nippers: Sharp-edged, plier-like tool used to fracture stone or ceramic tile.
Opus, opera (pl.): A work, a composition.
Opus Circumactum: A background, repeating pattern of interlocking fans or scallops.
Opus Musivum: Concentric rows of tesserae outline elements within the mosaic to the edge of the mosaic work.
Opus Palladianum: Randomly shaped and placed tesserae. Also known as crazy paving or cracked ice.
Opus Regulatum: Tesserae placed in a brick work pattern. Goutlines line up either horizontally or vertically but not both (one over two, two over one).
Opus Tessellatum: Tesserae placed in a grid pattern. Groutlines line up both horizontally and vertically.
Opus Sectile: Elements within the mosaic are cut from single blocks of medium, rather than composed of tesserae.
Opus Vermiculatum: A single, double, or triple row of tesserae that follows the contour of the subject or an element. The remaining background is composed of another opera.
Pavement: A floor mosaic.
Pebble: A broad category of naturally occurring stones. Usually river or beach worn. Used in the construction of pebble mosaics.
PEI: Porcelain Enamel Institute
Class 0 - No Foot Traffic: Wall tile only and should not be used on floors.
Class 1 - Very light traffic: Very low foot traffic, bare or stocking feet only. (Master bath, spa bathroom).
Class 2 - Light Traffic: Slipper or soft-soled shoes. Second level main bathroom areas, bedrooms.
Class 3 - Light to Moderate Traffic: Any residential area with the possible exception of some entries and kitchens if extremely heavy or abrasive traffic is anticipated.
Class 4 - Moderate to Heavy Traffic: High foot traffic, areas where abrasive or outside dirt could be tracked. Residential entry, kitchen, balcony, and countertop.
Class 5 - Heavy Traffic: Tile suggested for residential, commercial and institutional floor subjected to heavy traffic.
Pique Assiette: A form of mosaic making using broken china or pottery shards.
Plywood: Multi-layered manufactured board. Made from thin veneers of wood pressed together and held with a binding agent. The thickness of the wood layers and number of layers vary to provide a variety of dimensions and qualities. Used as backing (indoors).
Polished surface: Glassy smooth, reflective finish.
Porcelain Tile: A dense, impervious, fine-grained tile made by firing kaolin clay at a very high temperature. Low water absorption rate (less than 0.5%). Frost-proof. Porcelain tiles are much harder and more wear and damage resistant than non-porcelain ceramic tiles. Porcelain tiles carry colour and pattern through the entire thickness of the tile. Porcelain tiles are glazed or unglazed. PEI class 4 and 5.
Pre-grouting: Grouting a mosaic before it is installed or placed onto backing. The mosaic can be pre-grouted from the front or the back. The technique is used for a variety of reasons, such as: large interstices will permit adhesive to come through the mosaic to the surface; mesh-backed mosaic requires strength for transport; etc..
PVA: Polyvinyl acetate. A water soluble adhesive.
Reverse Indirect, Double Indirect, Double Reverse Method: A method of mosaic construction where the tesserae of a mosaic are placed upside down on a temporary backing. The finished (upside down) mosaic can then be transported to its final installation location or a permanent backing can be applied to the back of the mosaic and the temporary backing removed.
Riven: Pertaining to stone tesserae, the fractured sides as opposed to the saw cut sides. When a stone rod is processed using a hammer and hardie, each tessera will have two saw cut edges and two riven edges (plus the top and bottom).
Rod: A thin strip of stone of varying dimension ready to be fractured into tesserae.
Safety Glasses: Glasses worn for protection from flying particles.
Scorer: Carbide-tipped scoring tool. Used to score and snap concrete backing.
Scoring: Preparing media to be snapped. Scoring, usually with a carbide tip or wheel, creates a slight weakness along the score line, predisposing the media to “snap” along the scored line.
Sealer: A clear solution applied to a mosaic to protect the mosaic from stains and water infusion.
Sealing: The act of applying a sealant to a mosaic.
Slake: The chemical binding of lime with water. The slaking process is required to ensure proper thinset and grout setting.
Slate: A fine-grained, foliated, homogenous, metamorphic rock, derived from an original shale-type sedimentary rock composed of clay or volcanic ash. Not suitable for tessellation. 2.5 - 5.5 on Mohs hardness scale.
Smalti, Venetian Glass, Byzantine Glass: A type of hard-fired, handmade Italian glass with a vast range of colours and light-reflecting qualities. Considered the classic mosaic material. The original material of the Byzantines, it is still manufactured in small factories in Italy. The size of each tessera varies and the surface is uneven. This makes smalti unsuitable for work where a smooth surface is required, such as floors.
Smalto: Sheets of moulded smalti glass tiles.
Sponge: Natural or artificial sponge used primarily to remove excess grout.
Stained Glass: Glass that has been coloured by adding metallic salts during its manufacture. Typically worked sectile, but can be tessellated as well. Two to 6 mm in thickness.
Tessellate: The act of processing material into tesserae.
Tessera, Tesserae (pl.): The Latin terms for the basic unit from which a mosaic is composed: a small square, usually a cube.
Thinset: A cementitious adhesive. Used to adhere tesserae to backing.
Tile Cutter: A tool used to score and snap ceramic and porcelain tile. Many models are available; most employ a carbide scoring wheel.
Travertine: A porous stone formed by the precipitation of calcium from water having passed through limestone formations. Moderately difficult to work with as it tends to crumble. 3 - 4 on Mohs hardness scale.
Trowelling: The act of applying adhesive using a trowel.
Tumbled surface: Very lightly textured, flat, non-reflective finish.
Unglazed: Media without glaze.
Vitreous Glass: A glass manufactured in regular, smooth squares. Available in a wide variety of colours, including blended and metallic colours.
Wall Tile: A thin ceramic tile. Not suitable for flooring. PEI class 0 - 3.
Wet Saw: A water-lubricated diamond-bladed saw. Wet saws come in three configurations; band, ring, and circular blade.
Zillij: Arabic form of geometric mosaic making. Vast, complex mosaics that contain multi-pointed stars and other geometric patterns.