In the age of growing ecological awareness and sustainability, you can find many sources attempting to inform you about what materials are the most “green” for your kitchen and bathroom counter surfaces. The majority point to recycled glass as one of the top choices [see related articles and sources list]. However, pure cast glass is almost always left out of these “green” discussions in favor of mixed composites.

First plate glass is broken into “cullet”.

The term “recycled glass” is broad and can be claimed by fundamentally different materials. Both cast and composite surfaces contain recycled glass, but composites also contain a binding agent like petroleum based epoxy resin, cement, or others to hold the glass bits together. Cast glass consists of essentially one ingredient… glass. This material is created by breaking new or recycled plate glass into tiny pieces, called “cullet”, then reheating these into a molten state in a mold, forming a new and thicker slab of pure and luminescent glass.

Some might consider the focus composites manufacturers place on their recycled glass “greenwashing”, or choosing to focus on the sustainable aspects of their product while ignoring the higher impact aspects to capture a larger share of the eco-aware market.

By comparing these hard surfaces by some essential criteria, we can demonstrate without greenwashing that pure glass is an option worth discussing when looking for a sustainable counter material. This assessment is based on four dimensions of sustainability: carbon footprint of productiondurability and useful lifetoxicity/hygiene while in use, and post-consumer impact on the environment.

DIMENSION 1: Carbon Footprint

One of the most commonly accepted measures of sustainability is the carbon footprint, or the net amount of CO2 added to the environment by the production and transportation of that material. Most measure what is called “from-cradle-to-gate”, encompassing the harvesting and collection the raw materials, transporting them to the various production and fabrication locations, and the manufacturing and fabrication processes that result in the final product. This method comes from the widely agreed upon idea that CO2, a greenhouse gas, is one of the most significant contributors to climate change.

Glass is made from a common and sustainably harvested raw material – silicon dioxide aka silica. Found worldwide in the form of sand or quartz, silica is the most abundant mineral on the Earth’s crust [1], requiring less energy and creating less CO2 to procure than petroleum used in epoxy, large stone slabs and cement. It can almost always be found locally, requiring less energy to transport. The process to produce new plate glass requires intense energy in the form of heat, with sheets formed on a bed of molten tin [3]. New plate glass production generates about 0.789 kg of CO2 per cubic meter of cradle-to-gate finished product, which is 17% less than Portland Cement, and a tiny fraction of what is produced by ready mixed concrete or epoxy resin[2]. Glass really shines when you look at the carbon footprint when it is recycled. If left in a pure state, glass can be recycled at lower temperatures, using clean materials on hand, while reducing future waste headed for landfill.

Glassworks, Inc. currently recycles what is called “post-industrial” waste in the form of unused shower doors. Post-industrial material is made into a product by a factory but is either flawed or was made in excess of consumer demand. Rather than throwing these away, we have found that this glass works very well in cast glass counters and other kiln-formed glass products.

The carbon footprint is a useful standard, giving us a defined and measurable method of comparison, but falls short in isolation when trying to establish sustainability.

DIMENSION 2: Useful Life

The next measure of sustainability is the expected useful life of the product. The longer the useful life of the product, the farther we can spread the required CO2 and energy costs of production. We can create a simple equation to measure this by dividing the carbon footprint to produce by the expected life. Those familiar with the basics of capital investment may recognize this concept. By standing up to wear and tear, a product can become more sustainable by simply outlasting competing options and eliminating maintenance and replacement costs in ecological as well as financial terms.

The 301 Monroe blog has a great article called “Greenwashing” from Nov. 16, 2009 that compares many so-called “green” counter surfaces by this two-dimensional method. Unfortunately, cast glass was not included in their analysis, but their work is relevant none the less. They conclude that compared to household appliances like water heaters and air conditioners, the difference between various green materials is negligible (check out 301 Monroe‘s fancy graph). We can make a far greater environmental impact by installing better insulation, windows and reducing household energy consumption.

Contrary to common beliefs, glass is considered a durable material. Many of us have been hoodwinked by Hollywood to think that glass is exceptionally fragile and prone to breakage. It is dramatic to see actors smash bottles over each other in bar fights or jump through windows. Did you know that this “glass” is often made of sugar [4]? The truth of glass is that it is exceptionally durable, leading to its widespread use as a building material for interior and exterior applications for hundreds of years.

We have been providing durable and functional architectural glass since 1968, but we often find this bias when working with new customers. Cast glass has a Mohs scale hardness rating of up to 7, which is close to steel and similar to granite (also largely composed of silica) [5]. Our 100% glass counters have passed the tests of time and regular use, remaining intact and stunningly beautiful for decades.

DIMENSION 3: Toxicity/Hygiene

Toxicity and hygiene are easy to overlook when getting excited about the look and feel of a new material. The important factors to consider here are the possible interactivity between the surface material and the substances it comes in contact with, the emissions of volatile organic compounds (VOCs) and radiation, and how porous the surface is.

The last in the list, porous surfaces, are perhaps the easiest to understand. Any tiny pockets in the surface of a counter can grab microscopic bits of organic matter left behind when wiping it down. These can feed entire populations of harmful pathogens like bacteria. On a microscopic level, all counter surfaces have some degree of surface irregularities. Some materials are more prone to being porous than others. Cement, stone, and composites are more course materials by nature and require polishing to eliminate the tiny pockets. Cast glass from cullet has slight irregularities from the devitrification of the glass as it is reheated, but maintains a slicker surface without needing to be polished. A top sheet can also be added, which virtually eliminates all pores.

VOC’s are gasses emitted by materials throughout their useful life, though these are typically at their peak levels just after materials are produced and decline over time. In recycled glass composites, the culprit of VOCs are the binders. Acrylics and epoxy are petroleum products which are prone to some degree of “off-gassing” and can contain a number of potentially harmful chemicals such as phthalates [6]. Hardened epoxy resin can also contain Bisphenol A (BPA), which has been proven to harm human reproductive cells, and was reported by the US Food and Drug Administration to be harmful to fetuses, infants and children. Canada recently designated this as a toxic substance [7]. Cement binders are less harmful when set, but if they break free of the composite they can be irritating to the skin, eyes, and lungs [8].

Not included in the classification of “VOC”, the colorless and odorless byproducts of radioactive decay are risk factors in counter materials containing stone. Granite is mined from the earth and often contains trace amounts of uranium, which emits radiation and lung cancer causing Radon gas. Scientists say that stone counters typically only emit trace amounts of radiation and pose no immediate health risk [9]The New York Times covered one story of a woman with a more exotic stone counter that turned out to be “hot” with uranium deposits. Materials for home use are generally tested for radiation and VOCs. With normal use, you could expect only trace amount of toxins to be released by most commercially available materials.

The interactivity of the surface is another important factor to consider. Any time you have a composite, the number of substances in the mix has increased, thereby increasing the potential interactions with common substances used in the kitchen or bath. Glass has been used for food and medical containers for hundreds of years, and is the favorite container for artisan brewers and wine makers for a reason. It does not interact with what it contains, preserving the peak flavor and integrity of its contents [10].

Fear not, cast glass surfaces are a great clean alternative. Glass emits no VOCs and is inert. Our cast glass is non-porous, making it easy to wipe clean with mild, non-abrasive cleansers. Pure and simple, glass is possibly the most hygienic and toxin-free surface available.

DIMENSION 4: Post-Use Impact

So, you engaged in exhaustive research to find the best material with the smallest carbon footprint to produce, the longest life, and you are not worried about trace amounts of toxins. So far there is no irrefutable reason to choose cast glass over other popular materials. Let’s look into our green crystal ball… peering years, decades, even centuries into the future. Eventually that shiny new counter surface will show some wear. Someone will drop a bowling ball on it, or you wake up one day realizing you went with a fad that is just so early 21st century. Or, maybe you sell your home to someone who then demolishes the whole thing to build a triplex. No matter the reason, eventually that new countertop will become someone’s trash.

Though possible, recycling cast glass is costly and is not currently viable. Barring advances in recycling methods, a cast glass counter would most likely be thrown into landfill like the rest. Fortunately, pure cast glass counters are essentially made of the same stuff that was found in or on the earth to produce it. Glass does not break down easily, but when it does, glass releases its pure elements and remains inert in the ground. Composites have a similar long life after trash, but when they do break down, they release all of their toxins and chemicals, increasing the toxicity of the fill and potentially any ground water if there are leaks. All ingredients of counter materials eventually find their way back to the earth, but pure cast glass decomposes into a more environmentally friendly material.

We prefer to be purists whenever possible, and with the exception of a few dollops of installation adhesive and the infrequent use of paint, we focus on creating stunning custom designs in pure glass. We do this because we appreciate the enduring properties of glass and the skill required to manipulate it. Nothing captures and reflects light like pure glass. It is not surprising to us that something so simple would also prove to be friendly to the environment in the long run.

– – –

The long overdue effort towards cleaning up our environment and taking care of the earth through sustainable products has encouraged companies like ours to develop architectural materials which attempt to meet the “green” criteria. This article was written to increase awareness of the sustainability of pure glass (both recycled and new) and to encourage the examination of cast glass alongside other recycled glass surface options that, although purport to be sustainable, may use glass as only one ingredient in a less sustainable and sometimes toxic mix. Forty years of working with glass for counter tops, room dividers, vanities and other architectural elements has deepened our expertise and appreciation for the clean and sustainable properties of glass. Its comparable carbon footprint, long useful life, non-toxicity and hygienic qualities, and low post-use impact make pure cast glass a viable and noteworthy option in sustainable counter materials. Next time you are looking for a new counter material that is both stunning and sustainable, please reflect on pure cast glass.


[1] Wikipedia: Silicon dioxide

[2] Korea LCI Database Information Network

[3] Wikipedia: Float Glass

[4] eHow: How to Make Sugar Glass

[5] Wikipedia: Mohs scale of mineral hardness

[6] USGBC Green Home Guide: “Choosing Kitchen Countertops: Our Top Picks”

[7] Wikipedia: Bisphenol A

[8] The dermal toxicity of cement

[9] New York Times: “What’s lurking in your countertop?”

[10] Glass Packaging Institute: Wine, Beer & Food

Other Sources & Related Articles:


GreenHome.com: Recycling Glass

The Green Building Center


Radiation in your own home?

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