Blown Glass

Page history last edited by Bernardo Martinez 3 years ago

Overview

This page is for students working on the Blown Glass video podcast. It will have the following features:

Student notes from their individual research, edited into a draft script
Revisions by team members and the Subject Matter Expert (GayWyn Quance)
Questions to ask the SME and others during the interviews at the sites
Transcripts of video clips of the interviews and tours
Final approval by the SME and company PR people

Team

Bernardo Marinez: History of blown glass
Alex Anderson: Chemistry for coloring and making glass; properties of glass
Johnny Cantlin: Process of creating a blown glass vase or platter; hazards

Timeline

Initial Research: Jan., 2009
Detailed Research/Draft of Script: Jan., 2009
Contact with SME: Jan. 16, 2009
Tour of Companies (Videotaping): Jan. 27-31, 2009
Capture and Transcription/B-Roll Creation: Feb. 3-7, 2009
Final Script Complete with Approval of SME: Feb.10-12, 2009
Video Editing - Draft: Feb. 13-21, 2009
Alpha Testing/Revisions: Feb. 24-28, 2009
Beta Test/SME Checkoff: Feb.28-Mar. 5, 2009
Export to Podcast/Add Metadata: Mar. 5-9
Post to Blog, Upload to iTunes: Monday, Mar. 12

Script Sections:

Lead In:

History of Blown Glass:

The earliest evidence of blown glass comes between 34 B.C to 4 B.C. around Milkva, an old Jewish Quarter in Jerusalem. Pieces of glass tubes, rods, and blown bubbles were found. Some of the pieces of glass that were recovered were fire-closed at one end and the other end was partly inflated. Not only is this discovery the first attempt to make glass blown art, but also helped the artist understand the way glass reacts in different uses.

During the first century B.C., the Roman Empire encouraged glass blowing, especially during Augustus’s ruling. The first workshops during this time were in Syria, Palestine, and Cyprus. Eventually glass blowing reached Egypt and flowed though the Mediterranean, on the island of Samothrace, near Greece and the island of Corinth. Back in Rome, during the middle of the first century, Phoenician glass workers showed their glass work and techniques by build their studios near Italy. Later on, more glass blowers and workshops started to pop up around Italy, for example Campania, Morgantina, and Aquileia. They made many objects, like unguentaria (container for perfume), table ware and windows. Glass blowers continued to move into the rest of Europe opening workshops in the northern Alps, now known as Switzerland and others in parts of now France and Belgium.

Some of the few evidence recovered was blow pipes made out of clay, also known as mouthblowers, and clay molds. Clay blow pipes were made by glass workers dating the late first century. Many used clay blow pipes due to the availability of clay before the use of metal for blow pipes. The most prolific glass blowers were in Cologne, near the Rhine River in now Germany. There, they discovered stone and terracotta base mounds, which suggest the beginning use of mold-blowing technique. There were also blown flagons, blown jars with ribbon, and perfume bottles with the initials CCAA or CCA. These initials stand for Colonia Claudia Agrippiniensis.

During the middle ages, the Franks found the way to manipulate glass by using simple corrugated molds and creating claw decoration technique. The mound-blowing technique was used by Venetian glassworkers to create fine glass ware, also known as cristallo. Glass blowing, using coupled cylinders and using "crow methods" **comment by Gay Wyn - I am not sure what you are meaning here with "crow methods" ... team blowing ie crew blowing had been inpractice for a long time and allowed larger and more complex pieces to be made ... however, I am not familiar with the term "crow methods"**, made sheets or flat glass that was used for windows during the late seventeenth century. By this time, glass blowing was spread all over the world. People were blowing glass in China, Japan and the Islamic territories. Glass workers, during the Byzantine Empire, made mound-blown glass with Jewish or Christian symbols between the sixth and seventh century.

During the 1960’s two men, Harvey Littleton, a ceramic professor, and Dominick Labino, a chemist, created a workshop at the Toledo Museum of Art, where they experimented with melting glass in a furnace and blowing it, creating the studio glass movement. This movement spread all over the world, where artist like Dale Chihuly, Dante Marioni, Fritz Driesbach, and Marvin lipofsky. **comment by Gay Wyn - you might want to explain the defining characteristics of the American Studio Glass Movement and how, as it spread to Europe, it introduced new ideas and approaches to glassblowing. After all, glassblowing in Europe considerably pre-dated the American Studio Glass Movement ... ! **

Process of Blown Glass: **question from Gay Wyn - I am presuming the following description is for modern glassblowing - so steel pipes are being used, as versus clay pipes ... my edits are based on this presumption**

The First step is they melt the glass in the furnace so it becomes completely molten. It will act like a vicious liquid.
The second step is to heat the end of the steel blowpipe in the furnace so it is glowing red hot. If the end of the pipe is not heated, the molten glass will not adhere to the pipe. The molten glass will shrink back from the cold steel of an unheated pipe.
The third steps to gather the glass on the end of the blow pipe. This is done by dipping the blowpipe into the molten glass and rotating the pipe in the molten glass to evenly coat the bottom 4 inches of the pipe with glass, then carefully withdrawing the pipe from the molten glass, with the 'gather' of glass now on the end of the pipe.
The fourth step is to shape the glass onto the marver into a cylinder, centered on the pipe. the apparent color does change, however the actual color of the glass (ie the color of the glass when it is is cold) does not change. As the heat goes out of the blow pipe, the red glow, indicating very hot steel, dissipates.**
The fifth step is to blow down the length of the blowpipe, through the mouthpiece. A bubble will begin to form in the molten glass (the 'gather') at the end of the pipe.
The sixth step is to pick up subsequent 'gathers' on top of the initial gather until there is enough glass on the end of the pipe to make the intended blown object. Shape it on the marver and inflating it until you’re close to the size you want for the finished piece.
The seventh step is to add a neckline and finalize the bottom of the piece using a jack or the marver. You will than smooth the glass until the vessel will be able to sit level.
The last and final step is to transfer to a punty ** comment from Gay Wyn - you might want to explain what a punty is ... and how the punty attaches to the bottom of the piece with only a fragile glass-to-glass join ... ** and finalize the shape of the top portion using the hand tools. You will than remove it from the punty and place in the cooler for slow safe cooling so the product does not crack. ** comment from Gay Wyn - you might want to talk about the coefficient of expansion of glass - that glass shrinks in size as it cools and that unless this cooling is done slowly enough, the accumulated stress causes by this shrinkage will cause stress cracking of the glass ... the glass needs to be cooled sufficiently slowly that the shrinkage stresses can equalize out. This is the purpose of annealing the glass pieces. **

Science of Blown Glass:

Glass is considered to be an amorphous solid or a vitreous substance. Both refer to a substance which lacks any real long-range order of atoms. This lack of arrangement is due to the rapid cooling of the glass. This rapid cooling and fragmented arrangement of atoms causes the formed glass to be weaker in strength than the compounds used to create it.

Manufacturing: The most commonly used and manufactured glass is called soda-lime glass. In this mixture Silica (Quartz) should consist of 65-75% of the mixture with roughly 10% of the mixture being Sodium Carbonate (soda ash), and another 10% of Lime. In this mixture soda ash is added and decomposes to Sodium Oxide and carbon dioxide, the carbon dioxide is an unused by-product and will just bubble out of the mixture while in production. The sodium oxide then reacts with the silica and breaks some of the Silicon-Oxygen bonds in the network. This then drops the atomic stability of the silica resulting in a much lower melting temperature (roughly 1450 degrees Celsius instead of 2300 degrees Celsius). This addition of soda ash causes the glass to be water soluble though so Lime is added to reinforce the chemical resistance of the glass.

Glass products include three types of materials:

Formers: Formers are the basic ingredient in glass, they can be almost anything as most materials can be melted down to a glass state. Most commercial glass is made with the former Silica

Examples: Silica, Anhydrous Boric Acid, Anhydrous Phosphoric Acid.

Fluxes: These are used to help formers melt at lower and easier to maintain temperatures.

Examples: Soda Ash, Potash, Lithium Carbonate.

Stabilizers: A stabilizer is added to the finished glass to help keep it from dissolving, crumbling or falling apart.

Examples: Limestone, Litharge, Aluminum Magnesia, Barium Carbonate, Strontium Carbonate, Zinc Oxide, Zirconia.

*edited* Coloring: The coloring of glass is done by adding various metallic compounds **comment from Gay Wyn - the 'raw' metal is not added ... metallic compounds are added , eg. Cobalt Oxide** to glass during its manufacture. Examples of such metals include: iron oxide, cobalt oxide, manganese oxide, chromic oxide/potassium dichromate, tin oxide, copper oxide, gold, selenium, sulphur.

*edited* Properties of modern glass:

The properties of glass will vary based on the formula that is being created, these are just general attributes of glass and may not apply to all formulae.

Strength: Glass actually has a great amount of strength which is only really diminished by surface imperfections and differences between molecular bonds within and on the outside of the glass.

Hard: Its surface resists scratches and abrasions.

Elastic: Glass will give under stress but, will rebound back to its original shape with the release of stress. This applies only to a certain breaking point. **comment by Gay Wyn - when talking about glass strength, it is a lengthy conversation ... strength characteristics include tensile strength, strength under compression, rupture point etc. Glass has a very high tensile strength, which is shown in its use for fiber optics. Heat treating glass changes its strength characteristics - improves them. Modern formula of glass, eg borosilicate glass, has a much lower coefficient of expansion and is 'stronger' (less fragile on temperature changes) in day to day use (rapid changes in temperature) than the older formula soda glass. **

Chemical Corrosion-resistant: It is affected by very few chemicals and it resists most industrial and food acids.

Thermal Shock-resistant: withstands intense heat or cold as well as sudden temperature changes. **only modern formula resist sudden temperature changes!!**

Heat-Absorbent: retains heat rather than conducting it.

Optical Properties:

Reflects

Bends

Transmits

Transmits light with great accuracy

Electrical Insulating: Strongly resists electrical current. As you look up at transmission towers, the wires are supported on the towers by glass insulators.

Hazards:

Some of the hazards of blown glass are short term, some are long term. You can get skin burns. Over time, you can also develop eye damage (cataracts) or lung damage (silicosis) over time if proper work safety practices are not observed. Proper eye protection (welding glasses) that cut out the damaging light from the glory hole and furnace are necessary to protect your corneas. Proper practices in handling the silica and raw glass is necessary to prevent inhaling small shards of glass. Our bodies have no way of dissolving glass shards, they stay imbedded in the lung tissue, causing longterm damage.

~~With a furnace that puts out almost 2000 degrees Fahrenheit of heat it can be very dangerous for a am mature to experience with blown glass.~~

~~When they work they make sure they wear gloves and to not get to close to the furnace.~~ They also make sure they do not cool the blown glass too fast because if it drops temperature to fast it will crack and destroy all the work and effort they put in to the blown glass.

Interview questions:

How long does it take to master blowing glass?

What skills/education are required to be considered a blown glass master?

What are the different kinds of glass and what are the advantages of each?

What kinds of materials are needed?

How do colorizing agents react with glass?

What chemicals are used to color glass?

How do you get the different colors of glass and what are the chemicals used for?

What happens to the glass as it is heated to allow it to be moldable?

Do the properties of glass change if melted more than once?

What are the affects of impurities on glass?

What is the optimal temperature to work with glass?