An Orrefors 'Fishgraal' art glass vase, by Edward Hald engraved 'Orrefors Sweden/Graal nr. 2190/Edward Hald, 14 cm high. The Graal glass technique was invented at Orrefors Glasbruk in Sweden, in 1916. In simple terms, the glassmakers create a piece with different coloured layers of glass, allow it to cool, then cut a design in one of the coloured layers to create a pattern. Then they re-heat it and case it with more crystal, and expand it. Obviously, this is a very complex, time-consuming process. The more complex the process, the more likely are errors and the more likely is the creation of pieces which can't be sold, even though hours of time have been invested in them. A variation of the Graal technique is Fishgraal, invented by Edvard Hald in the 1930s. A design is painted on the glass, a green layer in this case, with liquid bitumen. Then, all the green layer which isn't covered with the pattern is acid-etched away, so that the pattern stands out on a clear background. Then it is reheated to 400-500 degrees Celcius and carefully covered with another thick layer of crystal. The name, Fishgraal, comes from the fact that the first collection featured fish. The designs are more detailed and the piece is not expanded, as they are in other forms of graal, so the designs are not distorted. Variations of this design were first drawn in 1936 and made until 1987. It is a classic of Swedish art glass