What to look for

All hand-blown glass is not the same.

The process is not an exact science and the nuances of heat, gravity, color and time all contribute to the success of a piece.

At Offhand Glass we have the skill and techniques necessary to create glass with everlasting beauty. Our broad experience with different types of glass, from the simplest vases to the most complex gallery-quality pieces, allows us to produce work of the highest caliber.

The beauty of quality hand-blown glass is subjective, but there are some accepted criteria.

Mechanically there should no scratches, cracks, pits or holes in the body. Small bubbles are acceptable, even desirable. The glass should not be too thick or thin. Colors should be translucent or opaque, incorporated as they were intended. The colors and their patterns may be pleasing or they may clash, but there should be a sense of association. The scale and elements in the piece should look proportional and correct.

A modest scar on the bottom of the piece called the punty mark is acceptable, proving the work was hand-blown and not cast or mold-blown. If applicable, the piece should sit flat on a surface.

A quality piece of hand-blown glass looks original. Its beauty is organic, eternal—almost an accident of fire and sand. This is our goal at Offhand Glass.


The Process

Glass blowing has remained largely unchanged in the last 2000 years (see our History section)—melting glass, gathering a molten piece on the end of a hollow metal rod, blowing air to inflate it, manipulating it to a desired form and allowing it to gradually cool.

However, though the basic process of glass blowing remains constant, each artist has their own technique and style. Bruce Greek, chief glass blower at Offhand Glass, explains how he creates a "simple" two-color vase from concept to completion:

“Depending on how complex the piece is, I spend a few days studying a sketch or drawing I’ve made and think about the shape, size and color. I usually work with a drawing; it helps me visualize the piece as it takes form.

"When I get to the studio I have a good idea how the piece will come out, and I appreciate the calm before the storm. Because of the heat of the furnaces and the glass, I'm always moving—constantly rotating the piece, standing up, sitting down, moving the glass around the studio—the medium demands it, gravity never quits.

"First things first, I turn on a little music.

"Then I check the glass in the furnace, where it's kept at a constant 2,150 degrees Fahrenheit. In this stage the glass is molten and colorless and it glows a bright white-orange.

"After checking for any trapped air bubbles on the surface (a few squirts with a water bottle will make them pop), I get the torch and light the glory hole. This large, round furnace is used to repeatedly heat the glass to keep it soft so it can be manipulated.

"There’s a yoke set up in front of the glory hole where I can rest the blowpipe and rotate the glass while it’s inside. The torch is also used to light the pipe warmer—a small oven where the blowpipes and punties are kept hot.

"It’s important to position the bench comfortably near the glory hole, where I sit and rest the blowpipe to rotate and work the glass. The tools needed for the day’s work are set on a small table next to the bench.

"I take five sheets of newspaper stacked together and fold them in half until they’re the size of a washcloth and about an inch thick. It’s called the rag and it sits in a bucket of water to soak. A few blocks are also kept in a bucket of water next to the bench.

"I position the torch in its stand near the bench and get out the color we need for the day. I usually use frit because I like the good layered depth and translucence it can create. The colors are arranged in trays and put on the marver.

"Next I turn on the annealer. It’s where we will put the finished piece to gradually cool without cracking.

"The glory hole is hot, the blowpipes and punties are hot, my assistant’s at my side—the work begins.

"I dip the end of the blowpipe in water. If the metal is too hot it might throw off air bubbles when it comes into contact with the hot glass. I open the furnace door and stick the blowpipe about two inches into the hot glass, turning the pipe a minimum of three times and scooping up an egg-sized amount of glass. (The amount of hot glass on the end of the blowpipe is called the gather.) It’s about the consistency of honey on a spoon.

"I pull the gather from the furnace and let it cool for 30 seconds, rotating it so centrifugal force keeps the hot glass on the pipe, then go back to the furnace for another gather built up onto the existing gather—maybe to the size of a small apple.

"After pulling the gather from the furnace I go straight to the frit, rolling the gather through the frit covering the surface with the color chips. Then I immediately go back to the glory hole. Resting the blowpipe in the yoke, I move the gather covered with the frit into the glory hole. Rotating the piece, it takes about 30 seconds for the frit to melt into the glass. Looks like chocolate chips melting into a cookie.

"I take the gather out of the glory hole, apply the second layer of frit and go back to the glory hole repeating the process. The second layer of frit melts into the first layer, but it’s important to understand that glass colors don’t mix like paint to make a third color. Mixing blue and green doesn’t make purple, it makes blue and green separately represented in the glass. If you want purple, you use purple.

"After the frit is melted into the glass, I pull the gather from the glory hole and sit at the bench. The blowpipe is just above my lap and resting on the bench rails. The gather is attached to one end of the pipe extending out from the bench rail.

"I sit at the bench rolling the blowpipe back and forth across the bench rails, rotating the gather to keep it from falling off the end of the blowpipe. I use a block and cup the piece as it’s spinning, cradling it and applying pressure, shaping it for maybe 45 seconds. This is called 'blocking.'

"Now it’s back to the glory hole with the gather for more heat, then a second blocking.

"With the glass very hot, I blow into the blowpipe and quickly cap the end with my thumb to trap the hot air inside. If it goes right, the air becomes superheated and expands the hot glass forming a bubble.

"The gather is now the size of a softball. After it has cooled for a minute, I go back to the furnace for another gather and round of blocking, then a couple of more trips to the glory hole and blocking. This increases the size of the piece and maintains even heat throughout the glass.

"I heat again in the glory hole one more time, then move to the marver and roll the bubble across the metal surface a couple of times. This changes the shape of the piece and cools specific areas of the glass to control where it expands when I blow into it.

"Then it’s back to the bench to heat the shoulder of the glass with the torch to get ready for the separation. My assistant takes the piece to the glory hole for more heat and I get the jacks. I coat the jacks with beeswax so when the metal comes in contact with the glass it won’t bind.

"I get situated at the bench and he brings the glass to me very hot. It’s been in the glory hole for a bit, so this is probably the hottest part of the process for the glass.

"Sitting at the bench I rotate the blowpipe and cradle the piece with the rag as it spins, shaping it more. As I’m doing this my assistant blows into the pipe—about as hard as you would blow out a candle, then a little harder as the piece cools and begins to harden. From where he’s positioned he can’t see the glass so I have to tell him how much and when to stop blowing.

"Depending on the design, there may be 5-10 more rounds of the glory hole, the rag, and blowing into the blowpipe and manipulating the bubble.

"After the last rag, the piece is rotated while I use the jacks to score a line in the glass at the shoulder. This is called the jack line.

"I take the piece to the glory hole. My assistant gets a punty and goes to the furnace and scoops up a plum-sized amount of hot glass with the punty. It’s a little confusing here, because at this point the rod used to scoop up the plum-sized hot glass and the hot glass are together called the punty.

"I withdraw the piece from the glory hole and sit at the bench with the blowpipe across the rails and the piece extended out from the bench. My assistant immediately presents the punty to me. He holds it while I guide the end with the plum-sized hot glass to the piece. The goal is to attach the punty as close as possible to the exact center of the free end of the piece so when it rotates it will turn true.

"If it goes well, everything is attached and rotating as one—the punty, the piece and the blowpipe. The punty begins to cool and stiffen up."

Critical finishing steps

"This next stage is critical as several things can go wrong. If it isn't done just right the piece can crack and be ruined, or the punty can be too hot and not hold the glass so it falls off and breaks. The jack line can also be too cold and the piece can crack and be ruined.

"I torch a flame on the jack line, giving the punty a little more time to set up. I dip the tweezers in water—they have a little channel that holds water—and touch the jack line allowing a bit of water to run off into it. It may take a couple of applications and the water weakens the glass a bit.

"Then I tap the blowpipe with the butt of the tweezers. If it goes right, the vibration causes the weakened glass at the jack line to break and the piece cleanly separates from the blowpipe. With the piece now attached to the punty, my assistant takes it to the glory hole for more heat and rotation.

"The blowpipe is positioned into the steel crack-off barrel where any glass left on the end can cool and splinter off. My assistant presents the piece to me at the glory hole and I heat the top half of the glass to prepare to create the lip of the piece.

"I withdraw the piece from the glory hole and sit at the bench. Rotating the piece I insert the tweezers into the open end as my assistant uses the paddles and together we create the lip. We also make sure the glass is turning true on the punty. Then maybe 2-3 more rounds of the glory hole and tweezers and paddles for more shaping and manipulation.

"Then my assistant gets the Kevlar gloves and hood and positions himself in front of the piece. He gets ready to catch it as it will separate from the punty. I sit at the bench and torch the punty to soften it up. With the tweezers I make two or three deposits of water on to the punty then tap it with the butt end of the tweezers.

"Another critical stage. If it all works, the piece breaks off at the punty and falls into the arms of my assistant. He places the piece inside the annealer to cool overnight and at that point it is, 'In the box.'

"The next day always comes with a little surprise because the color and look of the piece is different when it’s cooled—we open the annealer and see what we have. I must admit even after thousands of pieces, it’s always great to open the door and see the finished work.”

Please note: we recommend that nobody attempt to blow glass without expert instruction.


Glossary

Annealer
An oven to put finished pieces where they can gradually cool. Hot glass must cool down slowly or it may crack and shatter. Annealers come in different sizes. A large one may look like a big pizza oven lined with heating elements and insulation. It takes twenty minutes for an annealer to heat up to a working temperature of 895 degrees Fahrenheit. A small computer regulates the gradual reduction of the temperature.

Bench
Where the glass blower sits to perform various glass blowing tasks. It may look like a short metal park bench with insulated sheet metal and high rails on each end. The glass blower sits in the bench and rests the blowpipe just off their lap with the ends resting on the rails. With the glass attached to the end of the blowpipe, the glass blower can then roll the blowpipe back and forth along the rails, maintaining centrifugal force so the soft hot glass doesn’t fall of the blowpipe.

Blocks
Small wooden hemispherical tools that are used to shape the gather into a sphere to prepare for inflation. They look like salad bowls with long wooden handles. A fruitwood set gets progressively larger in size. Dipped in water to create a cushion of steam, the glass is rotated while a block is applied cupping the piece. They also aid in preventing the hot glass from collapsing in on itself during rotation and have a slight cooling effect on the glass.

Blowpipe
A hollow steel tube about five feet long and one inch in diameter used to hold and move the piece around the studio as its being worked. From the initial stage of gathering hot glass from the furnace to creating the shape of the piece, the blowpipe is attached to the glass throughout most of the process. One end has a mouthpiece to blow into and the other has a small metal ring to help retain the hot glass.

Cast
A general term describing a number of techniques where hot glass is poured into a mold to form a desired shape. It is quicker and easier than hand-blowing a piece.

Color
There are three types of color: powder, frit and rod. Powder is the consistency of flour, frit the consistency of sand to pea sized gravel, and rod looks like a colored glass dowel two inches in diameter and couple of feet long. The different types of color all have their uses, but at Offhand Glass we mostly use frit as it can create good layered depth and translucence.

Furnace
An enclosed structure typically made of steel and fire brick that holds the hot glass in a ceramic vessel. 24 hours a day, seven days a week a one million BTU burner keeps the glass molten at a constant 2,150 degrees F. In this stage the glass is colorless and glows a bright white-orange. On the front of a furnace is a small, one foot square sliding door where a glass blower can access the molten glass using a blowpipe or punty.

Gather
An amount of hot glass collected on the end of a blowpipe or punty.

Glory hole
A furnace with a opening where a work of glass can be inserted to be reheated, typically fed by two 2” burners. A large one may look like a giant tin can, three feet in diameter, sitting on its side. In front is a sliding yoke where the blowpipe rests. The glass can be inserted through the opening in the door and rotated inside the glory hole. It can take 30 minutes for a typical glory hole to heat up to a working temperature of between 2,200 and 2,400 degrees F.

Jacks
A metal tool that looks like large tweezers used to score the jack line.

Jack line
A line scored in the hot glass near where it is attached to the blowpipe. It is where the glass breaks and separates from the blowpipe.

Lip
A surface on the glass that is a curved edge or rim.

Marver
A smooth, flat surface typically made of steel or granite, where hot glass is rolled in order to smooth or shape it. The glass blower can also use the heat absorption properties of the marver to control what parts of the glass cools quicker, thereby controlling what parts will expand when it is inflated.

Mold
A procedure where a mold, typically made of metal or wood, is used to further shape or decorate hot glass. Hot glass can be laid into a mold or partially blown glass can be blown into a mold. It can be an easy way to create a predetermined form or imprint a pattern on the glass.

Paddle
Made of wood and of various shapes and sizes, paddles are used to apply pressure to glass to create a certain shape and to flatten the bottom of a piece. They can also be used in an impromptu manner to shield the glass blower from intense heat as he is working the hot glass.

Pipe warmer
A small furnace where the ends of blowpipes and punties are heated. An attached metal stand sticks out to rest the blowpipes and punties as their other ends rest heating in the flame

Punty
Also called the pontil, a solid metal rod about five feet long that is used to hold a piece during the glass blowing process. An amount of hot glass is gathered on the end of it and it is then attached to the free end of the glass.

Punty mark
The mark on the glass left by the punty after it has been separated from the piece. Indicates a piece was hand-blown and not cast.

Rag
Five sheets of newspaper stacked on top of each other and folded in half to the size of a washcloth and about an inch thick. It is then soaked in a bucket of water. With a bare hand it is cupped against the hot glass to manipulate it as it is rotating.

Shoulder
Area of the hot glass where the jack line is scored.

Tools
An assortment of hand tools such as tweezers, jacks and shears used to manipulate the hot glass. Also refers to the blocks and rag.

Torch
A portable hand held torch used to reheat the glass when it is outside of any furnace. It can shoot a two foot flame. The torch is used to heat specific parts of the glass to keep it soft or to expand it. It is also used to light the glory hole and pipe warmer.

Tweezers
A metal tool used to manipulate hot glass and to deposit water into the jack line.

Yoke
A metal stand on rails situated in front of the glory hole. At the apex of the stand are a set of ball bearings where the blowpipe rests and can rotate freely. The entire apparatus slides forward allowing the blowpipe with the glass on the end to be inserted into the glory hole.
 
 
Back to top