Daum Nancy Glass Construction Techniques
Acid-etching – A technique developed in the middle of the 19th Century, which involves the controlled exposure of glass to hydrofluoric acid, and which was first used to carve the markings of thermometers, burettes and pipettes. Later it was used as a decorative technique for art glass. The first step is to draw a pattern on paper and then transfer the design on to the vessel itself by scratching it into the surface. Next, the parts not to be exposed to the acid are covered with an acid-resistant varnish and finally acid is applied using a brush, or the piece is dipped directly into an acid bath.
Applique – External relief decoration applies to the body of the vessel while it is still hot, such as threads, prunts and handles. Sometimes small lamellas only a few millimeters thick are applied to the vessel in order to obtain the look of cameo glass while avoiding the inherent difficulty of the process.
Cameo – A technique similar to the cameo cutting of stones and shells used by the ancient Egyptians and Romans, and revived in the nineteenth century. The technique involves cased glass, or the overlaying of several different layers of different colored glass, two or three and more rarely four or five, and then to acid-etch or wheel carve the design of one color on another in relief. The difficulty of this technique lies in the fact that the various layers must have the same dilation coefficient and the same thickness in order to avoid any breaking while the piece is cooling, or when working on the glass once it is cold. The composition of each colored layer of glass is therefore decisive and kept secret.
Enameling – The ancient decorative technique of cold-painting vitreous enamels onto the vessel, then firing the colors in a muffle kiln (a low temperature kiln used for re-firing glass with enameling and gilding).
Intercalary Decoration – Daum took out a patent for this technique in 1898. It consists of using basic vessel decorated with powdered colored glass, or enameled with a design, sometimes padded, etched or even carved. It is gradually reheated and an outer and/or an inner layer of glass blown over it. When finally annealed, the vessel is then etched, carved or polished to bring out the full effect of the internal decoration. The initial shape of the basic vessel can itself be changed or distorted during the final heating phase.
Martele – The literal translation is hammered. A decorative technique producing a multi-faceted surface by cutting off small pieces of glass with a stone wheel, used particularly as a background to the design.
Pate de verre – The literal translation is glass paste. A technique very similar to the cire perdue in matter of bronzes. It allows many details in the shape which are difficult to obtain with mold blown glass or simply torn with pliers and scissors. A plaster mold is made around a wax positive of the desired shape. Then an earthenware shell is made on the outside of the plaster and both are heated together in order to melt the wax vessel out. The glass is ground into a powder, missed with a flux and color powders, and the mixture is shaped and slowly re-fired in this mold under high temperatures for several days. The mold I removed to reveal the final piece, which is ready to be cleaned and polished.
Vitrification – This technique was mostly used between 1900 and 1914 and consists of rolling the hot glass on the marver in particles of metal oxide or powder made of colored ground glass, and re-firing to achieve a smooth and highly polished finish. The powder becomes fused and vitrified into the surface. The effect is further enhanced by polishing at the wheel. Patterns can then be acid-etched or wheel carved into the textured surface.
Wheel-carving – A pattern or design is carved with a rotating wheel covered with an abrasive (usually diamond) powder, either in relief (en camee) or hollowed out (intaglio).
Wheel-cutting – This technique operated in four steps: the proportioning, which consists of dividing the glass to set some marks; then the sketching, using the grinding wheel, followed by the cutting itself and finally the polishing of the piece.
