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Glass and Ceramic

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Glass

Description:  We love glass. It's inert, non-leaching, and 100% recyclable. It is elegant and can be shaped and coloured as desired in a non-toxic way. It does not absorb smells or flavors, is easy to clean, and can be produced relatively inexpensively as the raw materials are plentiful and largely naturally-occurring.

Yes, there are the issues of it being fragile and heavy and somewhat energy intensive to produce and transport, but when balanced with the key negatives of plastic (leaching, toxicity, fossil-fuel derived, energy intensive to produce, huge waste and environmental issues), we feel glass is far superior for many everyday uses.

And glass is not new. It goes way back. Evidence of human-made glass has been found dating back as far as 4000 BC. 

So what is glass? Glass is an amorphous solid material that once hardened is usually transparent and potentially brittle. By amorphous, we mean that it's physical structure is not ordered and fixed like a crystalline substance, such as a natural crystal. Glass exhibits what is known as a glass transition, meaning that it can transform from its hard amorphous state into a molten rubbery, almost liquid state when heated sufficiently - and it can transform back into the solid amorphous state by cooling:  hence it's 100% recyclability.

What is glass made of? The main materials for most consumer glass, which is a type of glass called soda-lime glass, are:  silica or silicon dioxide (commonly known as "sand," yes, that same sand you find on a beach), sodium carbonate (or soda ash, which is both naturally-occurring and synthetically produced), and lime (calcium carbonate, which is found naturally as limestone, marble, or chalk). So the basic chemical composition and production process for most commercial glass is as follows: 

  • Silica is the base material (usually about 70-75%), but has a very high melting temperature (about 1700 Celsius). 
  • Soda ash (usually about 12-15%) lowers the melting point of silica (to around 800 Celsius), making it easier to work with, but simultaneously making it water soluble and soft.
  • Lime is then added to make the glass water insoluble and more stable. The lime contributes calcium oxide (about 5-10%) and magnesium oxide (about 1-3%). And aluminum oxide (about 1-3%) is also often added to increase the stability of the glass.   

Another common and more durable form of glass is borosilicate glass. In this type of glass the silica is slightly increased (70-80%), the soda ash is decreased and in part replaced with boric oxide (7-13%), which has the effect of increasing its durability and thermal shock resistance. Thus it it less prone to breakage with fast extreme temperature changes. Many of the glass products we carry are made of borosilicate glass, such as our airtight glass containers

One other form of glass we wish to highlight, given it's continued relatively common occurrence and its toxicity, is lead glass, also known as lead crystal. With lead glass, the lime-derived calcium oxide is replaced with lead oxide (anywhere from 25-60% depending on the application of the glass) and most of the soda ash is replaced with potassium oxide. The result is a glass that has a high refractive index - making it sparkle brightly - and a relatively soft surface so that it is easy to decorate by grinding, cutting and engraving. These properties highlight the crystals brilliance making it popular for glasses, decanters and other decorative objects. But it is not safe, and in our opinion should be avoided completely.  

Typical Use:  The uses of glass are many...containers, dishware and kitchenware of all types, windows, mirrors, laboratory equipment, optical equipment such as lenses, binoculars and telescopes, fibre optics used for telecommunications and in medicine, glass tubes and light bulbs. Borosilicate glass is regularly used for common household oven and cookwares, laboratory apparatus, various high intensity lighting applications, and glass fibres for textile and plastic reinforcement.

Toxicity:  One of the key reasons we love glass is because it is so safe. It is generally completely inert (i.e., non-reactive and non-leaching) and is impermeable to liquids and gases. These inert and impermeable qualities of glass make it completely safe for food and drink usage. The safety of glass has been demonstrated in numerous studies and is generally recognized as safe by governments and legislation

The exception is certain types of glass that may have toxic lead or cadmium in them.  We discussed lead glass above, and Health Canada explains how lead may be released from lead glass containers - such as lead crystalware - into food and drink. As well, lead glass or other glassware with glazes may have lead or cadmium in the glaze which may also release into food or drink. 

Most non-crystal glassware sold in North America is going to be safe - it is usually completely inert soda-lime or borosilicate or tempered glass. 

Recycling Rate: Glass is generally 100% recyclable and can be recycled endlessly without losing its properties (quality, strength, functionality). Recycled glass is almost always an ingredient (even up to 90%) in new glass containers.

According to the US Environmental Protection Agency (EPA):

  • There were 11.6 million tons of glass in the municipal solid waste (MSW) stream in 2012.
  • About 28 percent of the glass was recovered for recycling.
  • Glass recycling increased from 750,000 tons in 1980 to more than three million tons in 2012.

Our Suggestion:  SAFE, but AVOID LEAD GLASS AND LEAD CRYSTAL.

  

Ceramic

Description:  Ceramics can be broadly divided into two categories: traditional and advanced/technical. They are most often crystalline, but may also be semi-crystalline or - like glass - amorphous. Like glass, they are made by heating the raw materials and cooling them until hard. The traditional ceramics are most commonly earthenware pottery for dishes and artistic creations made with clay, kaolinite (or kaolin, often used for porcelain), quartz, feldspar, silica and/or cement. Advanced or technical ceramics exhibit enhanced properties and are usually made from carbides (such as silicon carbide), oxides (such as aluminum oxide, or alumina), nitrides (such as silicon nitride). Properties: hard (they can be harder than steel), wear-resistant, brittle (especially traditional ceramics), opaque or clear, temperature-chemical-acid resistant, corrosion resistant, low thermal and electrical conductivity (or some can have high thermal and electrical conductivity), insulating.

Typical Use:  Like glass, ceramics are extremely versatile and have many uses and applications...

Traditional: glassware, pottery, porcelain, dinnerware, tiles, bricks, sculpture and other artistic creations.

Advanced

  • Aerospace: space shuttle tiles, thermal barriers, high temperature glass windows, fuel cells
  • Consumer Uses: magnets, knives, ceramic tiles, lenses, home electronics, microwave transducers
  • Automotive: catalytic converters, ceramic filters, airbag sensors, ceramic rotors, valves, spark plugs, pressure sensors, thermistors, vibration sensors, oxygen sensors, safety glass windshields, piston rings
  • Medical (Bioceramics): orthopedic joint replacement, prosthesis, dental restoration, bone implants
  • Military: structural components for ground, air and naval vehicles, missiles, sensors
  • Computers: insulators, resistors, superconductors, capacitors, ferroelectric components, microelectronic packaging
  • Other Industries: bricks, cement, membranes and filters, lab equipment
  • Communications: fiber optic/laser communications, TV and radio components, microphones

Toxicity:  Like glass, ceramics are generally inert and safe. One concern could be the glazes used on a ceramic, as there is the possibility of the glaze containing toxic lead or cadmium. This is unlikely with ceramics made in Europe and North America for food use, but if unsure check with the manufacturer or artisan.  

Occupational inhalation exposure to raw materials used in ceramic production can be a problem, most likely due to the silica content in ceramic dust. Even short periods of exposure can be associated with respiratory symptoms, and chronic respiratory disease with long term exposure. This can be prevented easily through the use of proper personal protective respirators and appropriate ventilation systems to remove ceramic dust in the air. 

Recycling Rate: Very low. Ceramic recycling is minimal and ceramic is not accepted in most recycling municipal programs. Given the diversity of ceramics and the common use of glazes recycling is complicated. Re-use is more realistic - for example, broken pieces of ceramic are commonly used to create mosaics for artistic and home renovation projects.

Ceramic products such as paving and roof tiles are common waste products of the construction and demolition industry and they may be crushed and used as drainage material or rock base for driveways. 

Our Suggestion:  SAFE, as long as any glaze is free of lead or cadmium. 



IMPORTANT NOTES: While we strive to provide as accurate and balanced information as possible on our website, Life Without Plastic cannot guarantee its accuracy or completness because there is always more research to do, and more up-to-date research studies emerging -- and this is especially the case regarding research on the health and environmental effects of plastics. As indicated in our Terms & Conditions, none of the information presented on this website is intended to be professional advice or to constitute a professional service to the individual reader. All matters regarding health require medical supervision, and the information presented on this website is not intended as a substitute for consulting with your physician.

Throughout our website, some technical terminology is used. In the interest of making the articles accessible and not too long, dry, or complex, technical terms may be hyper-linked to more detailed explanations and relevant reference material provided in Wikipedia. Please keep in mind that Wikipedia articles are written collaboratively by volunteers from all over the world and thus may contain inaccuracies. Life Without Plastic makes no guarantee of the validity of the information presented in Wikipedia articles to which we provide links. We suggest you read the Wikipedia General Disclaimer before relying on any information presented in a Wikipedia article. 

 

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