Tracy Harris Gallery
During slumping, the glass is heated to a temperature where it gets soft and then "follows" the contours of an object underneath. The temperature determines how much of a curve the glass is allowed to follow, with more heat imparting a more elastic nature to the glass, allowing for more compound curves. The section below details the different slumping techniques used.
Full Fusing
Tack fusing is using heat to join together multiple pieces of glass without heating the whole item to the point that it changes shape. The smaller items heat up quicker than the carrier piece, which allows brief increases in temperature.
Fused glass is glass that has been placed and fired in a kiln at temperatures ranging from 1,099 degrees Fahrenheit to 1,501 degrees Fahrenheit. The technique used to create the fused glass item plays a large part in determining the temperatures used in the kiln. The following sections describe these different techniques.
When using the mould slumping technique, a flat sheet of glass is placed over a mould especially made for this process. Once the glass heats up, it "slumps" into the mould though the force of its own weight. The mould itself is perforated to prevent air bubbles from forming.
Mould Slumping
Tack Fusing
The fusing technique joins the glass together through the use of fusion welding. The piece maintains its general shape when using the lower temperatures of tack fusing but becomes a flat surface again when undergoing full fusing. Each fusing technique is described below.
Slumping Technique
Fused Glass
Fusing Techique
Moulds for this type of slumping are composed of a ring that allows the glass to fall through the opening in the center, which in turn forms a bowl. If a kiln shelf is used, the bowl will have a flat bottom, as the shelf catches the falling melted glass. The temperature in the kiln and length of time primarily determine the shallowness or deepness of the bowl.
Casting Technique
Free Falling Slumping
Casting is a process where glass is brought to a liquid state before being placed in a mould. Unlike metal casting, though, the soft glass does not flow through the mould and thus retains the variations within the glass, such as different colors and inclusions.
Usually done for decorative effect, the full fusing technique uses a much higher temperature than does tack fusing. Any pieces added to the surface of the main piece are absorbed into the surface, which becomes flat again.