History of Glass
Glass is an inorganic solid material that is usually clear or translucent with different colors. It is hard, brittle, and stands up to the effects of wind, rain or sun.
Glass has been used for various kinds of bottles and utensils, mirrors, windows and more. It is thought to have been first created around 3000 BC, during the bronze age. Egyptian glass beads date back to about 2500 BC.
Mosaic Glass
Modern glass originated in Alexandria during the Ptolemaic period, artisans created "mosaic glass" in which slices of colored glass were used to create decorative patterns.
Glassblowing
Glassblowing was invented during the 1st century BC by the glassmakers of Syria.
Lead Crystal Glass
During the 15th century in Venice, the first clear glass called cristallo was invented and then heavily exported. In 1675, glassmaker George Ravenscroft invented lead crystal glass by adding lead oxide to Venetian glass.
Sheet Glass
On March 25, 1902, Irving W Colburn patented the sheet glass drawing machine, making the mass production of glass for windows possible.
Glass jars and Bottles
On August 2, 1904, a patent for a "glass shaping machine" was granted to Michael Owen. The immense production of bottles, jars, and other containers owes its inception to this invention.
Collection and Processing
Two common ways to collect glass are at the curbside and at drop-off locations. Glass collected at the curbside is usually commingled, meaning that different colors of glass, and sometimes different types of glass, are collected together. This glass might then be sorted by color, or other characteristics, at a materials recovery facility. Some municipal and commercial recycling programs require participants to separate clear, brown, and green glass. Often, glass collected at drop-off locations is separated by color. Generally local recycling offices or departments of public works instruct residents on the types of glass that the recycling program collects and how residents should set out materials at the curb or drop-off centers. Curbside collection requires less work on the part of residents, although contamination levels can be greater.
Although all glass is made of silica and soda, the type and quantity vary slightly with different types of glass. These differences frequently cause manufacturing problems due to different melting points and chemical incompatibility. In addition, since neither brown nor amber glass is used to manufacture clear glass, it is important to sort glass by color. Glass separated by color, whether this takes place at the curbside or drop-off facility or at a materials recovery facility, yield glass cullet of higher economic value.
Sorting also can help reduce common contaminants, such as ceramic cups, plates and pottery, clay garden pots, crystal and opaque drinking glasses, heat-resistant ovenware, lead collars from wine and champagne bottles, stones and dirt, light bulbs, metal caps, lids and neck rings, and mirrors. Finally, sorting can keep broken glass from contaminating other recyclables, like newspapers.
In the materials recovery facility, workers remove large contaminants by hand and sort the glass by color where possible. Then, glass is typically crushed and travels by conveyor belt through a series of refinements. Magnets pull out metal, and air currents remove lightweight material such as paper. Some cullet suppliers use sophisticated equipment such as lasers to sort colors of crushed glass and further remove small contaminants. Scientists continue to develop mechanisms to improve materials sorting, and, therefore, the quality of the cullet.
Facts about recycling:
- Glass containers are 100 percent recyclable, can be recycled endlessly and recovered glass is used as the majority ingredient in new glass containers.
- An estimated 80 percent of recovered glass containers are made into new glass bottles.
- According to the EPA, 34.5 percent of glass beer and soft drink bottles and 28.1 percent of all glass containers were recycled in 2007.
- In some states, like California, glass bottle recycling nears 79 percent.
- Americans recycle nearly 13 million glass jars and bottles every day.
- The glass container industry has an annual revenue of $5.5. billion, with almost 50 manufacturing plants located throughout the U.S.
- The typical glass processing facility can recycle up to 20 tons of glass per hour.
- Glass containers produced today are 40 percent lighter than when they were 20 years ago, making them much easier to recycle.
- Every ton of glass that is recycled results in one ton of raw materials saved to process new glass, including: 1,300 pounds of sand, 410 pounds of soda ash and 380 pounds of limestone.
- Glass containers come in four different colors: clear, blue, brown and green; glass must be separated by color to ensure that new glass is not created from a mix of colors.
- Most recycling programs will only accept glass containers, because other glass products such as drinking glasses, lightbulbs, mirrors and Pyrex are treated with contaminants when manufactured.
- A 2005 study by the Beverage Packaging Environmental Council found that 18 percent of glass bottles are consumed at bars or restaurants.
- Americans generated 13.6 million tons of glass in the municipal solid waste (MSW) stream in 2007.
- About 24 percent of the glass was recovered for recycling.
- Recovery increased from 750,000 tons in 1980 to more than 3.2 million tons in 2007.
- Soft drink, beer, food, wine, and liquor containers represent the largest source of glass generated and recovered for recycling.
- Glass in durable goods, such as furniture, appliances, and especially consumer electronics, round out the sources of postconsumer glass.
