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Shaping Glass

Blackstone River Glass Center:

Specialized Glass Blowing Workshops in RI

Welcome to the Wonderful World of Hot Glass.

Also known as a super-cooled liquid!

Here is a little preview of some facts and terms you will learn at your lesson.

Glassblowing involves three furnaces. The first, which contains a crucible of molten glass, is simply referred to as "the furnace". The second is called the "glory hole", and is used to reheat a piece in between steps of working with it. The final furnace is called the annealer, and is used to slowly cool the glass, over a period of a few hours to a few days, depending on the size of the pieces. This keeps the glass from cracking or shattering due to thermal stress. Historically, all three furnaces were contained in one structure, with a set of progressively cooler chambers for each of the three purposes.

Tools:

The major tools used by a glassblower are the blowpipe, punty (or punty rod, pontil ), bench, marver, blocks, jacks, paddles, tweezers, newspaper pads, and a variety of shears.

Blowpipe:

The tip of the blowpipe is first preheated; then dipped in the molten glass in the furnace. The molten glass is "gathered" onto the end of the blowpipe in much the same way that viscous honey is picked up on a honey dipper. This glass is then rolled on the marver, which was traditionally a flat slab of marble, but today is more commonly a fairly thick flat sheet of steel. This process, called marvering, forms a cool skin on the exterior of the molten glass blob, and shapes it. Then air is blown into the pipe, creating a bubble. Next, the glassworker can gather more glass over that bubble to create a larger piece. Once a piece has been blown to its approximate final size, the bottom is finalized. Then, the molten glass is attached to a stainless steel or iron rod called a "punty" for shaping and transferring the hollow piece from the blowpipe to provide an opening and to finalize the top.

Bench:

The bench is a glassblower's workstation; it includes places for the glassblower to sit, for the handheld tools, and two rails that the pipe or punty rides on while the blower works with the piece.

Blocks:

Blocks are ladle-like tools made from water-soaked fruitwood, and are used similarly to the marver to shape and cool a piece in the early steps of creation. In similar fashion, pads of water-soaked newspaper (roughly 15 cm (6 in) square, 1.3 to 2.5 centimetres (0.5 to 1 in) thick), held in the bare hand, can be used to shape the piece.

Jacks:

Jacks are tools shaped somewhat like large tweezers with two blades, which are used for forming shape later in the creation of a piece.Paddles are flat pieces of wood or graphite used for creating flat spots such as a bottom. Tweezers are used to pick out details or to pull on the glass. There are two important types of shears, straight shears and diamond shears. Straight shears are essentially bulky scissors, used for making linear cuts. Diamond shears have blades that form a diamond shape when partially open. These are used for cutting off masses of glass.

Design:

There are many ways to apply patterns and color to blown glass, including rolling molten glass in powdered color or larger pieces of colored glass called "frit". Complex patterns with great detail can be created through the use of cane (rods of colored glass) and murrine (rods cut in cross-sections to reveal patterns). These pieces of color can be arranged in a pattern on a flat surface, and then "picked up" by rolling a bubble of molten glass over them. One of the most exacting and complicated caneworking techniques is "reticello", which involves creating two bubbles from cane, each twisted in a different direction and then combining them and blowing out the final form.

 

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