Saturday, September 29, 2012

Antique glass decoration techniques

Many techniques may be applied to glass objects to produce different types of decoration, both internal and external. We will mention here some principal types of decorations.

Internal decoration

Cased. When one layer of glass is applied over another, or when three or more layers are fused together and then outer layer or layers cut away (cameo).

Acid cut cameo glass vase
Simple coloured tint. The glass is mixed with a metallic oxide while still in powder form.

Latticinio. Clear glass embedded with white glass threads giving the appearance of spiral fluting. The threads are woven into the semi-molten metal.

Lithyalin. Opaque glass which shows visible striations of various colours and, when polished, gives the appearance of agate.

Marqueterie de Verre. Shaped and coloured lumps of glass presses onto the body of a vessel and carved after the glass had cooled. It is found mostly on Art Nouveau glass by Emile Galle.

Marqueterie de Verre
Millefiori. Meaning literally "a thousand flowers", slices of coloured glass canes are embedded in clear, molten glass to form flower heads or other patterns. Used on paperweights, jugs and other tableware.

Opaline. A translucent, milky white glass, which, by adding various metallic oxides, could be coloured pink, mauve, turquoise, green and several other shades.

Opaline glass egg shaped box
Zwischengoldglas. The German term used to describe gilt and coloured enamel decoration literally sandwiched between two layers of glass.

External decoration

Acid etching. The surface of the vessel is covered with an acid-resistant medium such as varnish or gum and the design scratched through with a sharp tool. The piece is then exposed to hydrofluoric acid, resulting in shiny, matt or frosted decoration of the exposed area. 

Applied. Glass trailed across the surface or applied to the sides of vessels in the form of small, circular blobs known as prunts in clear or coloured glass.

Cameo. Cased glass in two or more layers, with the outer layer carved on the wheel to create a design in relief.

Cut decorated glass vase
Cut. Facets and grooves made by cutting into the surface of glass with a wheel of iron or stone. Done in ancient times and taken up again by the Irish and English industry in the late 18th and 19th centuries.

Enamelling. Fine glass powder mixed with metallic oxides to give colours which are painted onto the surface of the piece then fired to fix them.

Moser enamelled glass
Engraving. Cutting a design into a glass with a sharp tool such as needle or wheel. Wheel engraving involves working the piece on a rotating wheel which acts as a form of grindstone to remove areas of the surface and create the pattern or inscription. Stipple engraving is achieved by tapping the surface of the glass in varying densities with a sharp needle to create a series of dots which build up into the desired pattern.

Intaglio. The technique of cutting or engraving a design below the surface of the glass to produce a relief image. the opposite of cameo carving.

Intaglio engraved portrait of Pericles, Greek hero
Flashing. Applying a thin layer of contrasting colour to the body of a piece by dipping it into thin, transparent, coloured glass enamel in liquid form. 

Bohemian flashed glass vase

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