A

absorbent paper

a paper used to make casts of mosaics, when soaked with water it becomes plastic and sticks to mosaic surfaces perfectly

adhesive

see binder

air-setting mortar

a mixture of water, aggregate and a non-hydraulic binder which sets in air but is dissolved by water such as lime or gypsum plaster.

andamento

the direction of the rows of tesserae; horizontal, circular, or sinuous lines

artistic glass mosaic

see smalti

aventurine

type of glass paste containing sparkling gold coloured particles. Vitreous mosaics containing aventurine have a fine gold grain on the surface. Exclusively employed as wall decoration.

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B

background

the area surrounding a figure. For example white or black on floor mosaics or gold on murals. The tesserae can either be set in straight rows or follow the contours of the figure.

bedding mortar

a layer of mortar which makes up the foundation of a mural or floor mosaic

binder

a substance used to bind particles together, ensuring consistency and solidification to the final product. The process of setting can be through the loss or absorbtion of moisture or by a chemical reaction. Binders most often used in mosaic are limes, cements, natural & synthetic resins.

blue frit

a blue pigment made by heating together silica, a copper compound, calcium carbonate and natron. The coloured compound was transported in pellets and used in shell mosaics of the 2nd half of the 1st century B.C.

bozzetto

a design reduced to a scale suitable for showing to client. The process know as squaring up is used to help transfer the smaller drawing to the full-size cartoon.

burnt lime

a caustic substance that is prepared by burning calcium carbonate limestone at approximately 900 deg. Celsius. At these high temperatures carbon dioxide is driven off and the limestone is converted to quick lime.

byzantine glass mosaic

see smalti

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C

cartoon

the full-size drawing on which the final mosaic is based. The cartoon is usually drawn onto brown paper in full colour and detail, it is then transferred to the surface to be worked on by the pouncing technique or simply traced over the main lines with a stylus.

caustic lime

see burnt lime

cement

see binder

cement mortar

a mixture of approximately three parts sand to one part Portland cement with water.

chip mosaic

mosaic formed from irregular chippings of stone, usually white in colour.

chopping machine

used for cutting stone and smalti into tesserae. It has two blades, the bottom one being fixed while the top one is moved by a wheel so that it falls exactly over the fixed blade.

commercial glass tile

see vitreous glass tile

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D

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E

emblema

a figured mosaic panel normally of small size. It is worked separately in the workshop either on a slab of marble or a terracotta tray with a raised edge as a frame. Emblemata (pl.)were then set into floor or wall mosaics made on the spot with a simple geometric design in tessellatum or sectile work. These panels were made in the style of paintings or or directly imitated paintings using minute tesserae (up to 50 per sq.. cm.)

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F

flat headed nails

to help plaster to bind to a wall, especially in cupolas, strong nails with large flat heads were hammered between the bricks so that the protruding heads acted as binders for the wet plaster.

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G

glass mosaic

see smalti

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H

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I

intarsia

A decorative technique in wood or stone in which pieces of different colour and equal thickness are cut to the shape according to the design and then attached to a support.

inlay

see intarsia

interstice

the space between each tessera, which is filled with grout

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J

joint

see interstice

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K

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L

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M

mortar

a mixture of binder, aggregate and water, which will set hard over a period of time

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N

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O

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P

pouncing

a technique used to transfer the design on a cartoon directly to the work surface. The design is pricked through along the contours and then pounced with charcoal dust so that the design is left on the surface underneath.The holes can then be lined up to have the complete design on the setting bed.

pigment

(a) a substance added to the glass paste to give it colour. It is usually a mix of metal oxides and salts. (b)a substance use to give colour to limestone based binders: either white or coloured marble dust, brick dust or other types of coloured sand can be added to the mortar mix.

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Q

quicklime

see burnt lime

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R

rainbow style

style of mosaic where the colours of tesserae are arranged in diagonal sequence instead of rows

rosin

Natural resin obtained as a solid residue from the distillation of crude turpentine from the sap of pine trees. Used as a mosaic binder in ancient Greece and Byzantine times.

rotino

A small grinding wheel turned by hand. It is used for shaping tesserae so that they join together perfectly.

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S

sectile

literally 'cut'; commonly used in the phrase opus sectile to signify a surface decoration obtained by cutting pieces of stone to special geometric or other shapes.

smalti

smalti refers to the coloured vitreous paste from which tesserae for wall mosaics are obtained. It is basically ordinary glass coloured with metal oxides. The molten glass is pressed flat to form the circular discs known as pizze. These are broken up into tesserae after they have cooled. Smalti is weather resistant and easy to cut, its choice of colours is nearly unlimited and they vary according to the type of oxide used in their making.

statumen

layer of rubble underneath the mortar bedding for a mosaic pavement

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T

tessera

the basic unit of mosaic. A small piece of glass or stone, or any other material suitable for mosaic work, cut to a square, rectangular, triangular or other regular shape.(pl.- tesserae)

tessellarius

craftsman who specialised in tessellatum

tessellatum

tessellated; commonly used in the phrase opus tessellatum to distinguish floor mosaic from wall mosaic and from opus sectile

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U

underpainting

a fresco painting on the top plaster coat when the mortar is still damp. This full size model was in full colour and served as a guide for the mosaic setters when fixing the tesserae. Red was a substitute for gold.

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V

venetian glass mosaic

see smalti

vermiculatum

literally 'worm like', commonly used to describe the technique of pictorial mosaics made with minute tesserae

vitreous glass tile

a mosaic glass used as a building material. The glass paste is basically the same as smalti, but the range of colours available is limited.Its reflective qualities are not as good. The making of vitreous glass is almost identical to that of smalti, except the vitreous pancakes are cut up into squares (approx. 2x2cm) by machine. These square tesserae are then mounted onto paper, which is stripped off after the backs of the tesserae have been applied to the work surface. Vitreous glass can also be supplied separately.

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W

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Y

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Z

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