A Glossary of Terms
Acrylic is a modern fast-drying paint containing pigment suspended in an acrylic polymer emulsion. Acrylic paints can be diluted with water when in use, but become water-resistant once dry.
Enamel, or ‘vitreous enamel’, is the result of fusing powdered glass, often in a paste form, to a surface through the process of firing, usually between 750 and 850 degrees Celsius. The powder melts and flows to harden as a smooth coating on metal, glass or ceramic. Vitreous enamel is hard, flame resistant, durable, and can take on long lasting brilliant colours.
Felt, one of the oldest types of fabric, is made by first separating and straightening wool using two combs with wire teeth called ‘carders’. Alternatively, the wool can be fluffed, or ‘teased’ by hand and stretched into rectangles. The carded or teased rectangles of wool are positioned to form a first layer, with all the fibres going in the same direction. The second layer is then positioned at right angles to the first and any subsequent layers are placed at a 90-degree angle to the last. Once all the layers are built up, dishwashing detergent is squirted over the wool and a sheet placed on top of it, which is walked, or danced, on until the wool is compressed into felt. Once compacted, the felt is squeezed of excess moisture and the sheeting removed. While still wet, the felt is then stretched and shaped then pinned to a firm surface until dry.
Gesso, meaning ‘chalk’ in Italian, is a powdered form of calcium carbonate. Traditionally mixed with animal glue, gesso is used as an absorbent primer coat for panel painting with tempera paints. It offers a permanent, brilliant white surface for painting. It is however brittle and prone to cracking, therefore unsuitable for priming canvases, unless first glued to a rigid surface.
Gouache is a water-based paint, but differs from watercolour in that the ratio of pigment to water is higher and an additional white pigment, such as chalk, is also present. This makes gouache heavier and more opaque, with greater reflective qualities.
Silverpoint predates the use of graphite as a drawing medium and was used by old masters such as Jan Van Eyck, Leonardo da Vinci, Albrecht Durer and Raphael. Renaissance artists used silver and occasionally leadpoint for underdrawings of their paintings or for separate studies on paper. A silverpoint drawing is usually made by putting silver wire in a holder, or wrapping it around a pencil, then drawing onto gesso or gouache primed paper or board. The slight tooth made by the layer of paint takes a little of the silver as it moves across the surface. The result is very delicate and marks are often built up using a cross-hatching technique.
Tempera, or temper, is used to bind pigments. Tempers include egg yolk (tempera), gum arabic, oil and egg white. Egg tempera is commonly associated with medieval painting, but in fact was most popular in Southern Europe. Tempera dries quickly and, for precision, it is often used in small strokes applied in a cross-hatching pattern. Although tempera cannot achieve the deep colour saturation of oil paint, unlike its more modern counterpart, tempera does not discolour with age, unless oil is added to the medium as an emulsion.