Tools

Blow Pipe (blowing iron):

A hollow stainless steel tube used to gather and inflate molten glass.

Punty (pontil):

A solid rod of stainless steel used to gather glass. Also used to gather a "bit" of glass for "sticking up" a finished piece.

Irons:

Blow pipes or punties.

Jacks:

Rounds jacks or blade jacks (puchellas). Jacks are tweezer-like tools used for shaping glass.

Block:

A piece of fined-grained wood with a hemispherical depression used to cool and shape a gather of glass.

Marver:

A sheet of metal used to cool and shape molten glass.

Shears:

Straight blade and "square" or "parrot" shears are used to cut hot glass.

Techniques

Hot glass is a viscous liquid. Learning glass blowing begins with learning how to use heat and gravity to control its flow.

Gathering: The object of gathering glass is to get a symmetrically distributed quantity of hot glass on the end of the iron. Glass which covers the iron is not usable (or even reusable).

To effectively gather glass, the iron should be warm enough for the glass to adhere to it. The tip of the iron should be reheated to a dull red.

When you are gathering glass, be careful to keep the glass on the iron as you withdraw it from the pool. If the iron is pulled directly back, much of the glass will flow off the end back into the furnace. The iron should be moved forward while raising it (and rotating it) to make the largest gather. The faster the iron is rotated in the molten glass, the larger the gather will be.

The furnace is, of course, very hot, and can be uncomfortable to stand close to. When the iron is in the furnace, it needs to be supported so that you will be able to work at arm's length from its end. When gathering, use the sill and the opening of the furnace to support the iron. When reheating, use the pipe support. When you withdraw your gather from the furnace, use the sill of the furnace as long as you can, but you will have to support the iron and its glass when you take it out through the door. Don't try to do this by holding only the cold end of the iron, or you won't be able to control the end with the glass on it. Slide your left hand toward the middle of the iron and use it as a fulcrum while you control the position and angle of the iron with your right hand.

The iron should be rotated at all times, at the rate which keeps the gather of glass centered. Tip the iron up or down to control the shape of the gather. Don't forget! Gravity will not take a break while you think about what to do next.

The glass as it is withdrawn from the furnace is too hot to work with. The next step is to cool the glass enough to be manageable. This is usually done by blocking the glass, or by rolling it on the marver.

Hot glass will not support any weight without deforming. To avoid making cold flat sides on the gather, start with your end of the punty below the level of the marver. The first part of the gather to touch the marver will have been cooled and stiffened by the punty. Gradually raise your end of the punty as you roll the glass on the marver to progressively cool it out to the tip. Roll the glass on the marver at the rate at which it is flowing to make the gather symmetrical.

Marvering and blocking shape the glass and cool it. If the iron is a punty, the block and the marver and gravity are usually the only means you will use to shape the glass. If the gather of glass is going to be blown, the shape of the pre-blown gather is quite important, but has more to do with the wall thickness of the final piece than it does with the shape of the finished piece.

Jacking: Sooner or later, you will want to remove the glass you have gathered on the iron. To do so, use the jacks just beyond the end of the punty to make it smaller in diameter and to make it colder. Begin jacking by rotating the iron back and forth on the arms of the bench, and using the jack to make a groove in the hot glass at about the end of the iron. Resist the temptation to pinch the glass; that will put two cold flat sides in the glass, which will resist any further efforts to make the circular construction you want. Gently use the jacks to make a groove around the circumference of the glass. The sides of the groove will be cooled and can be levered against to stretch and narrow the glass where it joins to the iron. Once this is done, the glass can be broken free by scoring it with a wet file and tapping upward.

Blowing: A blowing piece will usually require two or three gathers of glass. After making the first gather, you will need to blow a bubble. Almost any bubble will do, but if some bubble is not made in the first gather, it will be practically impossible to get the glass hot enough at the opening of the blowpipe to blow it later. It's a little tricky to make the first bubble. The glass has been chilled where it has made contact with the pipe, and it is just where the glass is coldest where the bubble must start. Once started, the bubble expands quickly toward the end of the gather - where the glass is hottest. This means that blowing hard enough to get the bubble started at all is likely to blow the bubble too thin. Somehow the air pressure in the pipe must be quickly decreased at just the right moment, and you cannot see when that moment occurs with your mouth on the blowpipe! The solution, adopted by virtually all experienced glassblowers, is to "thumb" the first bubble. Blow into the pipe, trap the pressure with your thumb over the mouthpiece, and hold the pipe so you can watch the bubble expand. Once it does, release the pressure.

This bubble will collapse if it is not cooled before making the next gather. A larger bubble blown will result in more glass taken with the next gather, but a larger bubble also increases the chances that the bubble will collapse.

Glass on a blowpipe which has had a bubble blown into it is called a parison. The beginning shape of the parison will determine the relative thickness of its sides and bottom after it is blown out - a short parison with wide edges wil blow out with a thin bottom and thick sides while a longer, narrower parison will blow out with a thick bottom and thin sides.