Mosaic, like any other "specialty" area has it's own lingo, acronyms and slang and, given the history of mosaic art, much of it is in Latin! Although it may look or sound difficult, it's really not -- and many of the words have a certain musicality or rhythm that seems especially well suited to an art form that involves finding the rhythm in laying the tesserae.
Pique assiette (also referred to as Picassiette) - A widespread, popular and versatile style of mosaic that incorporates pieces of broken ceramics and pottery, china, plates, dishes, cups, tiles, and other found objects, into the design. The term loosely translates from the French as "stolen plate".
GOG - An acronym for Glass On Glass referring to mosaics in which the tessera are glass (stained glass or tempered glass or plate glass) and the substrate is also glass.
Tessera (or "tess" for short); the plural is Tesserae) - A piece used in a mosaic. Originally it referred to the square or cubed pieces of stone in ancient classical mosaics, but now is used for pieces of any kind of mosaic material, whether they are ceramic, stone, pebbles, glass or some other substance.
Smalti (smalto is the singular) - Specilised mosaic tesserae made from richly coloured glass. Originally developed for Byzantine mosaics, the glass contains metal oxides which produce an almost infinite range of colour possibilities. The molten glass is poured into flat slabs which are then broken into individual smalti with rough, irregular surfaces that may be pitted with air bubbles. A thin layer of gold leaf can be embedded in smalti to produce gold tesserae. Smalti mosaics are normally ungrouted.
Andamento - the visual flow and direction within a mosaic produced by the placement of rows of tesserae. (for different styles, see opus, below)
Opus - Refers to a body of artistic "work" and in mosaic describes specific patterns of andamento as recognizable features in mosaics. Various "styles" of working the andamento by placement of the tesserae have recognized names or "opus". (see below
Opus circumactum - a technique for laying tesserae in fan-like patterns, usually used as a background. Often can be used to create movement. The fan-like patterns on the WIP in the pix to the right are small versions of circumactum.
Opus tessellatum - A description of rows of tesserae laid in regular horizontal or vertical lines. This style of placement is generally used in backgrounds.
Opus regulatum - As the name suggests, this is a very regular pattern of tesserae, like bricks in a wall, or squares on a chess board.
Opus palladianum - A random-like, crazy paving effect of placement of irregularly shaped, but similarly sized, mosaic tesserae, where the spaces between the tesserae have a largely uniform width throughout.
Opus Incertum - Similar to opus palladianum with random-like, crazy paving effect of irregularly shaped tesserae except that the tesserae are irregularly sized and the spaces between the tesserae are of irregular and uneven widths.
Opus vermiculatum - A single row, or several rows, of tesserae following the outline of a feature (such as a figure or other subject) in a mosaic. The effect can be a little like a halo, highlighting the subject and providing contrast against a background or can be used to create the effect of "movement" within the work. "Vermiculatum" means "worm-like" and is so called because it curves around the contours of the design and is laid evenly and consistently in linear or contoured rows.
Opus musivum - This is an effect rather like ripples on a pond, with repeated rows of tesserae laid in similar fashion to vermiculatum, but which spread out to fill the background to the edges of the mosaic area.
Opus sectile - This is a technique where, instead of being made up of lots of individual tesserae, shapes in a mosaic design are made from larger, specially cut, pieces (perhaps of tile, stone or stained glass) i.e. an entire leaf may be cut of one piece instead of created by may smaller pieces.
Direct method - A mosaic technique where the tesserae are stuck directly to the backing material. Basically, you are laying the tesserae face up onto the final substrate. When they have set, the mosaic will be grouted.
Indirect Method (also called the Reverse Method) The technique of sticking mosaic tesserae to a temporary surface and then transferring them all together to the mosaic site. Basically, you are laying the tesserae face down or "backwards". A typical method would be to first stick tesserae face down to brown paper with a soluble glue (such as wallpaper paste). The paper can then be reversed and pressed into an adhesive. When set, the paper can be sponged off to reveal the faces of the tesserae.
Double Reverse Method - The technique of creating a mosaic face up on a temporary surface then "flipping" it face down so that a temporary backing can be applied and the mosaic can be transferred to the final substrate by setting the back of the tiles into the adhesive. A typical method would be to lay the tessera out onto a work surface either without adhesive or using a temporary paste, then using either clear contact paper, a flat board or pan to contain the tesserae, to flip the mosaic over, apply paste and a temporary backing before transferring the mosaic to the final substrate and setting the back of the mosaic into the final adhesive. Used instead of the Indirect Method when attention to detail or complexity of design requires the mosaic to be created face up.
Tessellate - To tessellate a surface is to cover it with shapes without leaving any gaps. In mosaics, surfaces are often tesselated with irregular shapes fitted closely together. In mathematics, a shape is said to tessellate if copies of it can be arranged repeatedly on a flat surface without leaving any spaces. For example, squares tessellate (as on a chessboard), and so do hexagons (think of a honeycomb pattern). Octogons do not tesslate, but a surface can be tessellated with a combination of octagons and squares. Many striking geometric pavements can be created from different tessellations of geometric and interlocking shapes.