Sensibly Green Building an Environmentally Friendly Kitchen
Eco--friendly is a term that gets thrown about a lot these days. Everything claims to be good for the environment. Some actually is, but much of it is not. It is made to seem green by emphasizing elements that are green while ignoring those that are not at all eco-friendly, a process known as "greenwashing".
Determining which products and materials are truly green and which merely greenwashed is a challenge. But, if your goal is to create a kitchen that is friendly to the environment, the difference is critical to your success.
We are designers and builders, not fanatic environmentalists. So we are not going to outline the golden path to green nirvana. We are going to look at materials and products from the viewpoint of pragmatic greening – things that can be made greener without a lot of trouble and expense.
The goal is not ultimate greenness, but sensible greenness, not the greenest kitchen in town, but the greenest practical kitchen in town.
What Makes a Material Green
There are all sorts of formal definitions of eco-friendliness. Merriam-Webster defines it as merely "not environmentally harmful." But when it comes to choosing materials for a kitchen, the process is more complex than this simple definition would suggest.
Two questions need answers when selecting components and materials. First, is it healthy, and second, is it harmful to the environment.
Lots of materials common in kitchens are not at all healthy or eco-friendly. Vinyl flooring is a good example.
The Healthy Building Network characterizes Polyvinyl chloride (PVC) as one of the "most environmentally hazardous consumer materials ever produced". It is a health hazard throughout its life-cycle from manufacturing to disposal.
PVC is actually a form of fossil fuel, essentially solidified natural gas. It has a large carbon footprint. A lot of energy is required to turn natural gas into a solid. By one estimate,Note 1 greenhouse gas emissions from the manufacture of PVC are many times greater than those from all of the coal-fired power plants in the U.S.
The material is derived from ethylene. produced from naptha or natural gas liquids, and chlorine obtained from salt through an electrolytic process. In addition to copious greenhouse gases, its manufacture releases toxins into the environment including chlorine, dioxin, vinyl chloride, and ethylene dichloride, all known carcinogens.
Once installed in your home it continues to release lead, cadmium, and phthalates. Lead and cadmium are known to cause mental defects, especially in children. Phthalates are linked to childhood asthma.
PVC does not decay in landfills, and at the moment there is no known safe way to destroy it except through high-temperature incineration.
We live in a plastic society from which there is no escape. We can't get away from PVC in our kitchens. It is a component of cookware, microwaves, refrigerators, dishwashers, even faucets. But, we can reduce its use and impact by choosing substitutes, where practical, that are a lot less harmful.
For practical greenness, an eco-friendly material has these four characteristics:
- Sustainable: A material is sustainable if is or both. Either there is so much of it that the little we use is not missed or it naturally regenerates.
- Minimally Processed: A material used as close to its natural state as possible with minimal processing is likely to be greener than a material that requires a manufacturing using a lot of energy and generating a lot of waste.
- Recyclable: A material that can be reused at the end of its useful life or converted to something new is greener than one that cannot be reused.
- Bio-degradable: A material that is degradable (returning to its constituent elements within a reasonable amount of time) is greener than a material that is not degradable or degrades only over a very long time.
Let's start our search for a green kitchen with cabinets.
Cabinets, more than any other item, determine the style of a kitchen. Flooring, fixtures, lights, appliances, and even countertops are important but the cabinets define the kitchen's look and largely determine how well it functions. They are also the most expensive part of a kitchen, making up as much as one-half of the total cost.
Most cabinets these days are made of wood and wood products. A few decades ago, steel cabinets were in vogue and very common in Post-War kitchens, but fell out of favor in the 1960s. Plastic cabinets have migrated from offices and garages to gain a small foothold in kitchens, although mostly overseas rather than in the U.S. or Canada, so we can ignore these for the time being and focus on the over 99% of North American kitchen cabinets made of wood.
Wood cabinets contain three basic materials: wood, wood panel stock, and some sort of finish to protect the wood elements. All of these have some ecological issues.
Wood is a sustainable material. It is produced by trees that are cut into lumber Note 2 at a mill. The processing required to turn trees into usable lumber is minimal. Lumber, however, is just one of the products produced by milling. In a modern mill, every part of a tree is used. Anything that cannot be turned into a useful product is burned to produce the heat used to kiln dry raw lumber and to heat the mill. Sawdust, wood scraps, even tree bark are all used for something.
The material is sustainable. Trees can be replaced with new trees but only if trees are not cut down faster than they can be regrown. Overcutting is still a problem. Less of a problem now, especially in managed forests growing the common wood species used in most cabinets: oak, maple, walnut, ash, cherry, and pine.
Imported exotic woods such as wenge, teak, Bubinga, and mahogany are less well controlled for sustainability. Much of the tropical wood imported into North America is a gray- or black-market product, much of which is harvested illegally. But, these woods are also grown in managed forests that use sustainable practices.
The key to finding out whether a cabinet company uses sustainable wood is to look for certification to one of the recognized sustainability standards.
The non-profit Forest Stewardship Council® (FSC), founded in 1993 after the failure of the UN-sponsored Rio de Janeiro Earth Summit to reach an agreement on combatting deforestation. Its founding members included the World Wildlife Fund, the Rainforest Alliance, and other conservation groups, forest owners, timber groups and business leaders. The FSC enforces what is widely considered the most rigorous of the international forestry management standards. To become certified, a lumber company must agree to sustainable harvest levels and prompt replanting while protecting water quality, biodiversity, wildlife habitat, and the rights of indigenous inhabitants.
The Forest Stewardship Council also recognizes other sustainability standards specifically tailored to managing forests in the U.S. and Canada, including
- The Sustainable Forestry Initiative, to enforce sustainability while "meeting industrial wood-production goals" from the American Forest and Paper Association.
- The sustainability standard of the American Tree Farm Systemfor smaller, family-owned woodlots.
- The Sustainable Forest Management Standard created by the Canadian Standards Association (now the CSA Group) to protect forests in Canada.
All of these standards have also been endorsed by the National Association of State Foresters. Conservationists favor the FSC standards. Growers prefer the other standards. But they all do the basic job of helping ensure sustainable forests.
Cabinet Panel Stock
In days gone by, panels used to make the sides, bottoms, and tops of cabinets were made of boards glued edge-to-edge. This practice began to give way immediately after the Second World War in favor of plywood panels developed to make war materiel.
Today, panels of glued-up boards are rare except where historical accuracy is required. Engineered panels are a better material – stronger, more rigid, more dimensionally stable, and much less prone to warp, bow, or twist.
Engineered panels used in cabinets are of three basic types: plywood, particleboard, and medium-density fiberboard (MDF).
Plywood is made up of thin veneers (or plies) glued together. The product in its modern form dates to at least 1797 when Samuel Bentham, a British naval engineer, patented several machines to produce veneers.
Industrial production began in the U.S. in 1928. During the Second World War from 1939 to 1945, industrial capacity expanded to produce plywood as a war material in large quantities. After the war, inexpensive, high-quality plywood was readily available to the building industry.
MDF and particleboard are panels usually made of the leftovers from wood milling such as sawdust, chips, bark, and offcuts too small to be turned into lumber. They may also include agricultural waste such as bagasse (sugar cane stalks) and corn stalks and post-consumer waste that otherwise would end up in the landfill. Anything containing cellulose fibers will do.
The major difference between MDF and particleboard is the size of the wood particles used in their construction. To make particleboard, wood waste is ground into small particles (the "particle" in particleboard). To make MDF, the particles are steam-heated until they fall apart into cellulose fibers (the "fiber" in fiberboard).
For more information on plywood, fiberboard, and particleboard used in cabinet-making, go to An Introduction to Cabinets.
Engineered panels are good for the environment in several ways.
First, they use much less hardwood than panels built up from boards. Veneers stretch the availability of quality hardwood by using much less of it to make a cabinet. A full 3/4" of lumber is needed to make a 3/4" lumber panel. A 3/4" engineered panel uses a 1/32" veneer of hardwood. So the same 3/4" of hardwood makes 24 panels. The result is far fewer felled trees.
Second, waste wood and sawdust are the usual materials used to make MDF and particleboard panels – materials that would otherwise be thrown away. This again translates into fewer felled trees, with more of the available wood being used productively rather than discarded.
The trade-off, however, is energy use.
Panels are not minimally processed. Their manufacture requires a lot of energy to glue the panels under pressure (up to 280 pounds per square inch (psi)) while baking them at 284°F. But, considering that without engineered panels, the amount of wood used to make cabinets would be many times the current usage, requiring the harvesting of many more trees at a rate that probably would not be sustainable, we think the trade-off is acceptable.
There is the also issue of used in the manufacture of panels.
The usual adhesive is either urea-formaldehyde or phenol formaldehyde Note 3, synthetic resins that create a very strong bond. In the curing process, they release formaldehyde into the air.
Formaldehyde is a naturally occurring chemical found in very low concentrations in air and slightly higher concentrations in trees and some fruits and vegetables. In low concentrations, it is harmless, but in concentrations of greater than 0.1 parts per million, it is an irritant that causes mild to moderate irritation to the eyes, nose, and throat, and prolonged exposure to high concentrations can be dangerous. The EPA lists concentrated formaldehyde as a "probable human carcinogen".
To reduce any health risk to acceptable levels in the manufacture of wood panels, Congress passed a law entitled Formaldehyde Standards for Composite Wood Products, in effect as of December 2017. The rule caps the amount of formaldehyde that engineered panel stock may off-gas to 0.05 parts per million, one-half the amount that is considered dangerous.
Manufacturers are meeting this requirement by capturing and neutralizing formaldehyde emissions with chemical "scavengers" that convert the formaldehyde to a benign substance that has no know health or environmental effects. Note 4
The highest levels of emission occur during and immediately after manufacturing. Once the stock leaves the factory, emissions drop off rapidly. For a few weeks, the panels emit low levels of formaldehyde, but by the time they get to the cabinet shop, the emissions are usually too low to detect. (Having worked with panel stock for over 40 years, the author can confirm that, in all of that time, he has never detected even a whiff of formaldehyde from any engineered panel.) And, by the time finished cabinets are installed in your home, volatile formaldehyde from engineer panels is almost entirely gone.
But, if you are particularly sensitive to formaldehyde, there are options. Manufacturers are increasingly switching to other adhesives including soy-based binders and those based on polyvinyl acetate (also knows as Elmer's glue, white glue, or carpenter's glue) or methylene diisocyanate, which do not emit harmful VOCs. Panels using these adhesives are permitted to be labeled "No added formaldehyde".
But this is not the whole story. Even if the material does not off-gas formaldehyde, it may emit something equally obnoxious. To be certain that a panel is truly free of harmful VOCs of any kind, look for a Greenguard certification from Underwriters Laboratory (UL). Greenguard products meet the very strict low-emission standards of UL 2818 Greenguard Standard for Building Materials, Finishes and Furnishings. Greenguard Gold certified products comply with the even stricter requirements of California's Department of Public Health.
Cabinets are infinitely reusable. When you are tired of your old cabinets and replace them with new ones, you can still make use of them in the basement, garage, or workshop. And, if you can't, someone else can. One man's trash is another man's treasure, so donate them to your local ReStore to help out Habitat for Humanity. Also consider Goodwill Industries.
Many local charities also accept used cabinets to sell or use. In our town (Lincoln, Nebraska), the Marine Corps League looks after formerly active Marines down on their luck and will accept cabinet and furniture donations. Catholic Social Services helps folks find and afford suitable housing and is delighted to get used cabinets in good shape that can be reused.
If non-profits don't work out, try an architectural salvage company. Some will pay you a small sum for the cabinets, but if not, almost all will arrange to uninstall them for you.
There are a few donation rules. Doors and drawers should be in good working order, even if not pretty. Pretty can be added with a new coat of paint or varnish but missing and or non-working doors and drawers are a much harder problem to solve. Many charities will not accept cabinets with doors or drawers that are missing or do not work. Most charities will pick up cabinet donations, and some will uninstall them for you, which saves you the trouble of doing it yourself or the expense of hiring someone to do it for you.
Be sure to ask for a receipt. Your donation to any 403(b) charity is tax-deductible. To get an idea of the value of used kitchen cabinets, see the Restore Donation Valuation Guide. (Is this link broken? Please report this link as broken.)
For much more about cabinets, including styles, construction, and manufacturing, go to Cabinet Basics
Green Cabinetry Checklist
To ensure that your cabinets are sensibly green, follow this checklist.
- ☑ All wood used in the cabinet, including wood used in engineer panels is certified by the FSC or a similar organization to be from a sustainable source.
- ☑ Engineered panels are certified toxin-free by Greenguard or a similar program.
- ☑ The finish used on the cabinets is water-based or, if oil-based, is certified zero-VOC by Greenguard, GreenSeal or a similar program.
Countertops are the second most important visual element in your kitchen. They follow cabinets as the component that contributes the most to the look of the kitchen. They also need to be very functional. Countertops are, after all, the primary works surfaces in any modern kitchen and need to be durable and long-lasting, able to retain their good looks year after year.
In a green kitchen, we also want them to be as friendly as possible to the environment without sacrificing any of their critical functionality or durability. Fortunately, materials that beautiful, functional, durable, eco-friendly, and suitable for countertops do exist.
The rules for green countertops are fairly simple.
A material that …
- sustinable and
- used in or very close to its natural state,
- requiring only minimal fabrication
is likely to be green. Whereas, a material that …
- is not sustainable, and/or
- requires extensive manufacturing
- using lots of energy and eco-unfriendly chemicals
is very unlikely to be green.
Engineered Composite Countertops - Greenwashed, but Not Green
With these two rules in mind, let's look at a material often promoted as being green that really is not very eco-friendly: engineered composite or "quartz" countertops.
Composite countertops include Silestone from the Spanish company, Cosentino and Zodiaq by Dupont. They are a manufactured product made from from a filler material of some kind and a a plastic resin binder to hold the together.
The filler, which may be anything from crushed stone to bamboo fiber, makes up about 2/3rds of the material and gives the countertop its character. The rest is a chemical binder, a hard-setting plastic resin used to bind the filler particles together and make the product waterproof.
Not too many years ago, there was only filler material: quartz, hence the name "quartz countertops". Over time other stones and then non-stone fillers have been added. Filler materials used today, in addition to crushed stone and stone dust, include broken glass, metal shavings, sheets of paper, wood fibers, and bamboo.
The object of using all these new fillers is to get greener. Many fillers are either environmentally sustainable or contain a high percentage of post-consumer waste, or both, giving some composite countertops at least the patina of being a "green" material.
Engineered composites are all made much the same way: a filler material is mixed with a thermosetting resin and compressed under high heat and tremendous pressure in a large press while the resin cures. The most commonly used binder is a phenolic resin, a combination of phenol and formaldehyde with just a soupcon of methane that cures to a hard plastic.
The typical engineered composite is an example of the questionable practice of promoting a product as "green" because they contain some environmentally friendly components while ignoring others that are not-so-friendly. In total, the product may be about as earth-friendly as acid rain despite its green content. The practice is called "greenwashing."
Most composites are not green, just greenwashed. But, some are greener than others. The composite countertops that come closest to being friendly to the environment are Alkemi by Renewed Materials, Inc. and ECO by Cosentino.
Alkemi uses scrylic resin as a binder with a filler composed of scrap aluminum and copper flakes. The U.S. company has been certified for sustainability by SCS Global Services (formerly Scientific Certification Services) based on its use of up to 97% recycled materials in its made-in-USA countertops and an Advantage Gold certification for being VOC-free.
ECO is a composite material that uses 75% recycled scrap (salvaged mirrors, window and bottle glass, porcelain, and industrial furnace slag) as a filler. We don't know what the other 25% of the filler is made of, but presumably, it is not very eco-friendly, or the manufacturer surely would have mentioned it.
The binder, composed of 22% corn oil, is likewise promoted as a boon to the environment and heavily advertised by Consentino. The other 78% of the binder, which is the usual petroleum-based phenolic resin, is never mentioned. Still, the material is perhaps as eco-friendly as can be achieved with the high pressure and heat processes that require an enormous amount of energy. But, while greenish, it falls a few yards short of actually being green.
Natural Stone Countertops
At the other end of the green spectrum are natural stone countertops, probably the best choice for the eco-conscious kitchen.
Not every type of stone makes a good countertop. The stones commonly used include granite, limestone, marble, slate, and soapstone.
Stone processing varies slightly depending on the type of stone, but in general, stone is quarried in large blocks that are sliced into standard 2 cm (3/4") or 3 cm (1-1/8") slabs using a diamond saw. The rough slabs are honed or polished on one side to create a smooth surface, then shipped to local stone yards.
Stone that is quarried far away is less green than stone quarried locally. Transportation of heavy stone, particularly stone originating outside of North America, requires a lot of fossil-fuel energy and adds to the greenhouse gases accelerating climate change. So, the best choice for a green kitchen is a stone originating as close to where it will be used as possible. Note 5
When a countertop is ordered, the stone yard custom cuts the stone slabs into the sizes and shapes needed to make the countertop and smooths or shapes the cut edges. Energy use in this process is minimal and the only chemical involved is water.
The only health danger from stone is in its processing. Cutting and smoothing create stone dust that can cause silicosis, a lung disease caused by inhaling the silica in stone dust over a long period. The prevention is the standard particulate mask worn by stone workers. After processing, stone poses no environmental or health hazard.
Some stones, such as slate, are hard and resist scratches and heat. Others, like marble, are more delicate and require a lot of care and maintenance. Stone has no "give" at all so that a plate, cup, or glass dropped on it is likely to shatter rather than bounce.
Any stone can be scratched, but hard stones like granite and slate require quite a bit of effort to produce even a small scratch. Soapstone is very soft and is easily scratched. However, all but the deepest scratches can be buffed out with a ScotchBrite® pad.
Most stones are porous and need to be sealed to prevent staining. Stone processors can seal countertops using a resin applied to seal the stone and fill micro-fissures and indentations that can collect moisture, dirt, and bacteria. By filling in minor imperfections, the resin gives the stone a more flawless look. Factory sealants offer more lasting protection that does not need renewal for up to fifteen years.
Soapstone is a Little Different – In a Good Way
Soapstone is so chemically inert that it is often used as countertops in chemical laboratories. Even strong acids and ammonia do not affect it. It is an amazing conductor of heat, dissipating heat so rapidly that it can easily withstand the hottest pots and pans. Before a pan could get hot enough to harm soapstone, it would melt.
Soapstone is non-porous so it does not stain. Spills do not penetrate the material. Water spilled in it will show up as a dark spot, but that spot disappears when the water dries. Oil, however, does not dry, so an oil spot permanently dark.
The usual way of beating the oil-spot problem is preemptive oiling. Oiling darkens the stone so any accidentally spilled oily substances do not show. It also dramatically highlights the grain in the material.
Soapstone "sealers" and specialty soapstone oils are widely sold, but Madisyn Watson, installation manager for Vermont Soapstone maintains that a good-quality mineral oil applied once a week for the first few months is all that is needed. After this initial period, re-apply the oil whenever you see that water has stopped beading on the countertop.
Soapstone is extremely soft. Its main ingredient is talc (50-75%), one of the softest minerals known. The countertops will scratch, and there is not much to be done about it. Minor scratches can usually be removed with a green Scotchbrite® pad or 220 grit sandpaper. Closed coat wet or dry sandpaper made for metal is best.
Most soapstone fans, however, just leave the scratches, considering them a welcome part of the patina of the stone.
Stones that are not factory sealed need to be sealed by the countertop installer and the sealant re-applied every six months.
Natural sealants such as those used on wood are not very effective in protecting stone. The best and most durable stone sealants are synthetic products that are specifically formulated to shield stone surfaces from water and stains while allowing the stone to breathe and release moisture vapors. Sealants made for countertops are food safe, containing no ammonia, phosphates, or other harmful substances. But, to be sure, look for sealants that are identified as for countertops, food-safe or non-toxic.
Calcium-based stones (marble, travertine, and limestone) are very susceptible to damage by even mild acids in food and liquids such as vinegar or citrus juice. No amount of sealing will protect these stones from potential acid damage. They are better used in bathrooms rather than kitchens.
Stone is not renewable. We cannot grow stone. So, its claim to being a sustainable green material is not based on renewability but on inexhaustibility. We are unlikely to ever run out of rock.
Granite, for example, is so abundant that we cannot possibly use enough of it to make a difference before the sun explodes. It is 70-80% of the earth's continental crust.
The 375 million metric tons that are excavated each year will never make even a tiny dent in the 1.6 sextillion tons Note 6 of granite in the earth's crust. After a thousand years, we will have removed just 0.000000025% of the available granite, an amount so tiny that it won't be noticed.
Additionally, stone never changes its nature. Unlike wood which is produced from trees and once turned into wood cannot be remade as a tree, stone never changes. It starts out as stone. Throughout its lifetime as a countertop, it remains stone, and when it is finally discarded it is still stone. We never use up stone. We merely move it around – borrowing it for a time then returning it to the earth when we are done with it. It may be returned in a different shape and size, and in a different place from whence it came, but it is still, unarguably, stone.
Most discarded stone countertops are broken up and end up in landfills. Stone countertops are recyclable, but at this time are rarely recycled. There is no nationwide network for recycling stone countertops as there is for plastic, paper, and some metals.
The main problems with recycling countertops are weight and fit. Countertops are heavy and require special devices to move safely. They can be reused if the right fit can be found. But fit is almost always a problem. Countertops custom cut to fit one kitchen will rarely fit seamlessly into another, and countertop fabricators have little interest in re-cutting used countertops. Their interest is in selling new countertops.
Old stone countertops could be made into other products. Recycled Granite, for example, uses waste and cut-offs from countertops fabrication to make stone tile and paving stones, but no one as far as we can determine uses discarded countertops for such purposes.
So, at this moment, we have to reluctantly conclude that natural stone countertops, although theoretically recyclable, as a practical matter, usually cannot be recycled.
Despite its recycling limitations, however, we rank stone is the most eco-friendly of the countertop materials. It is a natural material turned into a countertop with minimal processing. No harmful chemicals are used or produced during its processing, and it is so common that the supply of stone can never be exhausted. Since the material is already in a natural state, the issue of degradation in a landfill does not arise.
Eco-Friendly Wood Countertops
Wood is a close second in environmental friendliness.
Despite the frequent warnings about the sanitation issues of wood countertops for food preparation, serious cooks often prefer wood countertops. And, as it turns out, the danger of wood countertops has been somewhat overstated.
Recent studies, such as the one by Deal Oliver at the University of California at Davis, have found that while bacteria tend to accumulate on both wood and plastic countertop surfaces in roughly the same concentrations, wood has natural antimicrobial qualities that help keep bacteria in check, while man-made materials do not. As a result, wood harbors much less live bacterial than most other kitchen countertop materials.
The types of wood used in countertops have expanded over the past few years. The varieties of wood available are no longer limited to just the traditional hard maple. Mahogany, ash, cherry, oak, mesquite, walnut, beech, and alder are all used in countertops.
Custom wood countertops are mostly a local industry, made to order in the exact sizes required by independent woodshops in the locality where they are to be used. But, the number of dedicated countertop manufacturers providing countertops nationally has greatly increased. Some of these will make custom sizes, but most limit their products to standard-size slabs intended to be cut to size by the countertop installer.
Local shops tend to be less expensive because they do not have to add long-distance shipping to their price. National manufacturers, however, often offer a wider choice of wood varieties.
Wood is a medium maintenance material. It is porous and will stain readily unless sealed. Typical hard coatings such as varnish do not work well on countertops because they are too readily damaged by routine food preparation activities.
The better sealants are oils and natural organic waxes, but which sealant is best depends on how you intend to use the countertop.
We recommend that you not cut or chop directly on a wood countertop. Use a chopping block instead. But, if you intend to cut or chop directly on the countertop, use a non-setting oil or wax. Examples are mineral oil, that is specifically formulated to use with food.
Non-drying finishes do not cure hard, so they offer only limited stain protection. They penetrate the surface of the wood to keep it from drying out and cracking, but stain protection is purely incidental.
Of the three, butcher block wax offers the most protection as the wax in the mix repels liquids. We use an initial two or three coats of mineral oil followed by butcher-block wax. Renew the wax every two or three months.
Countertops that will not be used as cutting or chopping surfaces should have a drying sealer like These oils contain resins that penetrate and soak into the wood before they dry. Once the resins have hardened, they provide a stain-resistant seal. An additional application is needed once or twice a year depending on how heavily the countertop is used.
Tung oil is more expensive but cures faster. Be certain that it is 100% tung oil, however. Some sealants labeled tung oil are actually blends of tung oil and varnish.
Linseed oil is easier to use and more forgiving of mistakes. Curing time depends on whether the linseed oil is "raw" or "boiled." It can take several weeks for each coat of raw linseed oil to cure.
Boiled linseed oil cures faster and is the better sealant. But, be careful to select an oil that is actually boiled. Many are not. Heavy metal driers like cobalt or manganese salts are added to accelerate the curing process.
For a true boiled linseed oil without the added chemicals, look for oil that is labeled "polymerized", "solvent free" or "FDA approved" for direct food contact.Note 7
Clean wood countertops with a few drops of dish detergent on a wet rag. Once clean, spray undiluted white vinegar on the countertop and let it sit for five minutes, then wipe it up with a clean, damp sponge or dishcloth. The vinegar safely sanitizes the countertop.
Never use chemical cleansers, especially those that contain ammonia (Windex, Forumla 409) or chlorine bleach. They will dry out the wood over time, making it easier for permanent stains to set in.
Countertop woods should be either locally sourced or certified sustainable. We cover what makes wood sustainable in the section on cabinets, above. (Click here to go back to that section. When you are finished, use your browser's back button to return here.)
Certification of sustainability is particularly important if you select an exotic wood produced outside of Europe or North America. Much of the tropical lumber from Africa, Asia, and South America is still taken from rain forests without regard to sustainability. So, you should ensure that the company you buy from is the final link in the chain of certified businesses that deal in responsibly harvested lumber. These are identified by an FSC "chain of custody" certification that ensures that every step of the process of turning trees into lumber complies with FSC standards.
Green Countertop Checklist
To ensure that your countertops are sensibly green, follow this checklist.
- ☑ All wood used in the countertop is certified by the FSC or a similar organization to be from a sustainable source.
- ☑ Stone used in countertops is quarried as close to the locality in which the countertop is to be installed as possible.
- ☑ The finish used on countertops is one of the natural oils or waxes such as linseed oil, tung oil or butcher block wax. If a hard finish such as varnish is used, it is water-based or, if oil-based, is certified zero-VOC by Greenguard, GreenSeal or a similar program.
Stone and wood may be the most eco-friendly of the common countertop materials, but are they the best material for your particular lifestyle. Find out about other countertop options at New & Traditional Countertop Choices where we rate countertop materials
Sensibly Sustainable Flooring
You have many options for your kitchen's flooring. These are reviewed in detail at Flooring Options for Kitchens and Baths. Many are intensively manufactured, using synthetic, primarily petroleum-based materials, and cannot be considered even remotely friendly to the environment. The materials that meet the criteria for environmental friendliness are stone, bamboo, cork, and wood.
The advantages of stone for flooring are the same as those for countertops. Since these have already been covered in detail above in this article, we will not restate them here (except to say that some types of stone used for countertops are rarely used for flooring. Soapstone is an example. It is much too soft).
In this section, we will consider the pros and cons of bamboo, cork, and, to a limited extent, hardwood.
Admittedly cork is not the first material that comes to mind when you think of kitchen flooring. Yet, it is about as close as we can come today to the perfect material for a kitchen floor. Durable but resilient, water-resistant, fire-resistant, sound-absorbing, and one of the most sustainable and renewable of green materials, cork's unique properties make it an excellent choice for a green kitchen floor.
Cork is the bark of the Cork Oak tree (Quercus Suber) an evergreen tree native to Southern Europe and North Africa. Most cork-producing trees are grown on plantations where the trees have a lifespan of 200 years and longer.
The bark is harvested by hand using methods that have remained essentially unchanged over the centuries. Once the tree has reached maturity (typically 25 years), the first harvest of cork bark is removed from the tree. The process is repeated at intervals of nine years (the minimum interval required by law in Spain and Portugal). During each harvest, no more than 50% of the bark is removed, allowing the tree to protect itself using its natural defenses. Each tree can be harvested multiple times during its lifetime.
The primary use of cork is to produce stoppers for wine bottles. Flooring is made from the waste material left over from making wine corks and increasingly from recycled corks. The cork scrap is ground into small granules. The granules are baked under pressure and steam in molds. Some cork is dyed, but more commonly the color in cork is the result of variations in baking time or temperature. The cork is then cut into tiles, planks, or strips, smoothed, and finished with several applications of a durable coating, commonly a urethane.
The binders typically used in manufacturing cork are urea melamine and phenol-formaldehyde. However, with the growing awareness of the problems of these synthetic chemicals, manufacturers have begun switching to natural, plant-based, resins such as suberin.
Cork contains micro-cells filled with air, about 2.4 million of them in each cubic inch of cork. This is what gives cork its resilience and buoyancy. Cork has a little "give" to it when it is walked on. but immediately springs back to its original shape. While cork can be dented if enough pressure is applied and the micro-cells are ruptured, ordinary use causes no damage. Damaged cork can be easily replaced.
Cork absorbs sound waves rather than reflecting them, resulting in a quieter kitchen. Cork does not burn. It is used as fire-resistant insulation. Hold it over a flame, and it will scorch, but it never catches fire.
Cork is also very water-resistant due to its cellular structure. One of its early uses was to make life preservers and fishing bobbers. But, allowing water to stand for long periods on cork floors should be avoided. It will probably not damage the cork, but it is likely to damage the subfloor under the cork as it trickles down between the cork tiles.
Cork can be installed on a subfloor with adhesive or allowed to float, interlocked but not attached to the subfloor. It is available in a variety of shapes including the traditional cork tiles and the newer cork planks and strip designed to roughly emulate wood planks and strips.
Properly installed, cork is a long-lasting floor, lending a warm, natural look and feel to a kitchen. It will retain its functional beauty for decades. Some cork floors have been in use for over 100 years. Cork floors in the reading room of the library of the U. S. Department of the Interior in Washington, for example, have been heavily trafficked since the 1890s.
The floor of the foyer of the U. S. Department of Commerce building in Washington, installed in 1930 by the Depression-era Works Projects Administration (WPA), is still in daily use.
Maintenance is simple. Damp mopping with a mild detergent is all that is needed to maintain the flooring. Cork does not stain easily or require scrubbing or cleaning with harsh chemicals. Periodic reapplication of finish is recommended. but never sand a cork floor.
If cork comes from Southern Europe, especially Spain or Portugal, it is well regulated by law to be sustainable. In Portugal, for example, it is illegal to cut down a cork tree without a government permit, and violators face jail time. However, to be doubly sure of its sustainability look for an FSC certification or one from the Programme for the Endorsement of Forest Certification (EFC). If the material originates in North Africa, sustainability is more loosely regulated, and an FSC Certification is a must.
Some cork is finished with low-VOC coatings, but VOC is not usually an issue. Even if the coating is high in VOCs, they will have long-evaporated by the time the product arrives on our shores from Europe or Africa after a three- or four-week sea voyage. However, if zero--VOC is the goal, look for Greenguard Certified by Underwriters Laboratory (UL). Greenguard products meet the very strict low-emission standards of UL 2818 Greenguard Standard for Building Materials, Finishes and Furnishings.
Hardwood is a traditional flooring choice for kitchens. Long before there was linoleum, laminates, or vinyl, there was wood.
Oak, either red or white, is the most commonly used wood for flooring in the United States because it's the most readily available. Other domestic species that are growing in popularity include maple, beech, birch, cherry, hickory, pecan, and walnut. Ash, like oak a ring-porous hardwood, which is dying at a rapid rate from the invasion of the Emerald Ash Borer, is starting to rival oak in price and availability.
Many of these woods are produced right here in Nebraska. See Guide to Nebraska Hardwoods for Cabinetmakers and Woodworkers, and are milled into flooring locally at a very reasonable cost. Local woods include some rather rare species seldom found commercially such as Hornbeam (Ironwood), Mulberry, and Kentucky Coffeewood.
Wood floors are available in both solid and engineered wood. Engineered wood is a manufactured floor in which a thin veneer of hardwood veneer on a substrate made of plywood.
Engineered flooring is a manufactured product that, like all plywood, requires a lot of energy to glue the panels under pressure while baking them to set the adhesive. The tradeoff, however, is that by using just a veneer of hardwood, it saves trees. Most engineer floors today are made with eco-friendly glues, but to be sure, look for a certification that the material is VOC--free.
Solid wood, on the other hand, is minimally processed but uses wood with more abandon. A typical 12' x 15' kitchen uses over eight board feet of hardwood. An engineered wood floor in the same kitchen uses about 1/3rd of a board foot, a significant saving.
One difficulty with engineered floors is that they cannot easily be refinished. So in about 10 years, when the flooring is showing substantial signs of wear, it can only be replaced. A solid floor, by contrast, is a 200-year investment that can be refinished over and over.
To ensure sustainability, be certain that the flooring complies with the Forest Stewardship Council® "chain of custody" standard which is particularly important if your preferred floor is a tropical hardwood.
Green Flooring Checklist
To ensure that your floors are sensibly green, follow this checklist.
- ☑ All wood, cork, or bamboo used in the flooring is certified by the FSC or a similar organization to be from a sustainable source.
- ☑ The finish used on the flooring is water-based or, if oil-based, is certified zero-VOC by Greenguard, GreenSeal or a similar program.
For more information on flooring of all types for both kitchens and bathrooms, go to Flooring Options for Kitchens & Baths (With Ratings)
Healthy Paints and Varnishes
There is a surprising amount of paint and varnish needed to finish a kitchen, about 12 gallons for an average 12' x 15' kitchen. Cabinets are painted or varnished inside and out. If you have a wood, cork, or bamboo floor, it too is finished in some sort of coating, usually a varnish. Walls are normally painted. Wood trim around doors and windows and wood baseboards are either painted or stained and varnished.
Paint and varnish are two types of what our friends in that industry call . Paint and varnish are liquid coatings – applied as a liquid that dries to a thin film by evaporation or curing.
There are other types of coatings. Much of industry uses what are called . These are sprayed on in powder form then heated in an oven to melt and bond the powder. The bonding changes the structure of the coating into long, cross-linked molecular chains that give the finish its durability.
Know it or not, you probably have powder-coated finishes in your kitchen. Most appliances finishes use this method.
The basic components of liquid coatings are some form of a binder and a solvent.
The type of solvent used determines the coating's classification. In water-based coatings, the solvent is water while the solvent in oil-based paints or varnishes is some synthetic version of the original natural solvent: .
The job of solvents is to keep the coating liquid until it is exposed to air. Once the paint or varnish is applied, the solvents begin to evaporate and as they evaporate a chemical reaction takes place that hardens the resins in the binderNote 8. When all of the solvents have evaporated, the solids in the cured resin remain behind as a thin but hard shell-like film.
If the coating is a varnish, the solids that remain are transparent resins that allow the grain of the cabinet wood to show through. If it is a paint, the solids also include pigments, usually inorganic compounds, that make it opaque and give it color.
The original binders were natural oils such as
Water used as a solvent in water-based paint and varnish does not off-gas any VOCs simply because water, while volatile, is not an organic compound. Any VOCs off-gassed by water-based coatings are from chemical dryers and hardeners that may have been added to the basic paint formula. These are usually very minor.
Oil-based coatings are a very different story. The chemical solvents in oil paints are themselves VOCs intended to evaporate into the air. It is this evaporation that hardens the paint. If they did not evaporate, the finish would never dry.
Evaporating solvents in oil paints are the source of the distinctive new paint smell. Solvents may include formaldehyde, aliphatic hydrocarbons, glycol ethers, acetone, and ethyl acetate, none of which is particularly good for you eye-, ear-, nose-, or throat-wise.
The key advantage of these synthetic solvents is that drying time is greatly reduced. In former days, paint and varnish could take months and sometimes years to fully cure. Today, most paints and varnishes dry to the touch in a few hours, although they may need several weeks to dry completely.
Two-part catalyzing coatings called conversion varnishes dry even faster and are the preferred finish of most large cabinet manufacturers.
Conversion varnishes contain a high concentration (40-60%) of solids that virtually ensure a two-coat application (a sealer coat then a finish coat). It cures through a chemical reaction rather than through evaporation. The hardening agent (catalyst) is kept separate until just before use when it is mixed with the varnish. Chemical curing reduces drying time, which in assembly-line manufacturing is an important consideration.
Most conversion varnishes off-gas formaldehyde for up to four weeks until fully cured.
The federal government imposes strict limits on VOC content in paint or varnish. The Architectural Coating Rule limits oil-based varnishes 450 grams per liter (450 g/l) or 3.75 pounds per gallon (3.75 lb/gal), low-gloss paint to 250 g/l (2.1 lb/gal), and all other paints (low-luster, semi-gloss, glossy, etc.) 380 g/l (3.2 lb/gal).
The good news is that by the time cabinets are delivered to your house, the coating is dry, and most VOCs have already evaporated. The other good news is that for most people, the VOCs, while obnoxious, have no ill effects. But, for those who are sensitive or allergic to even trace amounts of the chemicals, there are low- and no-VOC alternatives.
The most obvious low-VOC option is a water-based coating. A few years ago water-based paints were considerably less durable than their oil-based counterparts, dried more slowly, and did not provide as much coverage, so more coats were required.
Through better paint chemistry, these differences have now largely disappeared. Today there is no particular advantage to oil-based paints over water-based paints used indoors. So, no reason to prefer oil over water.
In varnishes, however, there are still differences. Water-based varnishes do not penetrate the wood to enhance the wood grain like oil-based varnishes. Nor are they as durable. For these reasons, oil-based varnishes are usually preferred by cabinetmakers.
If an oil-based varnish is your choice, there are low- and zero-VOC options, but be prepared to pay a few dollars more per gallon. For a coating to be considered a low-VOC finish, VOCs may not exceed 200 g/l (1.7 lb/gal), and zero-VOC coatings must be below 5 g/l (0.04 lb/gal).
Early low- and zero-VOC paints and varnishes were bad news. Manufacturer's simply removed a lot of the solvent to lower the VOC levels or changed the solvents to chemicals not considered to be VOCs by the EPA, including ammonia. One result is that the paint did not cover well, often requiring two or even three coats for complete coverage. They also omitted the fungicides commonly added to paint to combat mold and mildew, but which can off-gas VOC chemicals.
These products are now very much improved through new chemical formulations that allow reduced solvents without affecting the performance of the paint or varnish. In consequence, there is no longer a functional penalty for choosing low- or zero-VOC varnishes or paints and no reason not to do so if you are bothered by the idea of VOCs even in small concentrations in your new kitchen.
Choose wisely, however. There are some low- and zero-VOC paint and varnishes on the market that are not particularly low in VOC or which have substituted chemicals that, while not on the EPA list of regulated VOCs, are still very suspect. To ensure that a coating is truly low- or no-VOC, look for a product
- Certified compliant with Rule 1113: Architectural Coatings of the South Coast Air Quality Management District,
- Greenguard Certified by Underwriters Laboratory (UL). Greenguard products meet the very strict low-emission standards of UL 2818 Greenguard Standard for Building Materials, Finishes and Furnishings,
- GreenSeal certified to comply with the GS-11 standard for paints, coatings, stains, and sealers.
- GS-11 is the strictest standard. It not only limits VOCs but prohibits a comprehensive list of potentially harmful chemicals, including heavy metals, certain phthalates, triclosan, formaldehyde donors, known carcinogens, mutagens, reproductive toxins, hazardous air pollutants, and ozone depleting compounds.
Unused oil-based paint, stain, and varnish cannot be recycled. Before it is completely dry, it is considered by the EPA to be "hazardous Household Waste" and special disposal procedures must be followed. If completely dry, however, it is no longer hazardous and may be discarded with ordinary trash.
Water-based paints, stains, and varnishes can be recycled. Your city may have a paint recycling program. Many localities have transfer stations where these finishes can be dropped off. National recycling programs such as PaintCare, Inc., a program set up by paint manufacturers to recycle unused paint, operate in many states. New water-based paint can be made from recycled paint, or the paint mixed with other water-based paints for use where color does not matter, like over-painting graffiti and the interiors of most federal buildings. (Just kidding!)
If you cannot find a way to recycle, then, just like oil paint, let it dry completely and discard it in ordinary trash.
Green Paint, Stain and Varnish Checklist
To ensure that your finishes are sensibly green, follow this checklist.
- ☑ The finishes used in your kitchen are water-based or, if oil-based, are certified zero-VOC by Greenguard, GreenSeal or a similar program.
- ☑ Recycle unused water-based paints, stains, and varnishes. If thy cannot be recycled, dispose of them responsibly. Never put wet paint or varnish in ordinary trash. Let it dry completely first.
Almost Green, But Not Quite
Some materials are almost green but not quite, usually due to the extensive processing required to turn eco-friendly materials into a useful product. The best of these are bamboo flooring and ceramic tile. Both are made from sustainable materials, but undergo multi-step processing and require a lot of energy to produce. They are worth consideration for a sensibly green kitchen, however, if the greener materials do not suit your needs.
Raw bamboo in its natural state is one of the world's most environmentally friendly materials, used in Asia for many thousands of years as a building material. Bamboo flooring, however, is not in its natural state. It is highly processed and not truly green.
Although often classed with wood and frequently treated like wood, bamboo is not wood. It is the stalk of a grass, specifically Phyllostachys heterocycla var. Pubescens (commonly known as Moso bamboo). It grows very fast, about 1" each hour – so fast that the human eye can actually watch it grow. It also grows very tall, as tall as a three-story building before it is harvested.
There is little danger of exhausting the material. Its harvest cycle is 4-6 years compared to a harvest cycle of 80-100 years in managed timber forests. It is harvested without the need to replant because the root system remains intact, so the plant simply regrows, very much like the grass in your lawn after your mow it. In a certified sustainable forest, only 20% of the bamboo is harvested annually.
Flooring made of bamboo is a manufactured material. Fabrication requires a lot of heat and pressure and typically uses unfriendly chemicals such as urea-formaldehyde as a binder.
Whereas wood flooring is a board minimally milled to create tongue-and-groove flooring. Bamboo does not naturally occur in a rectangular shape and must first be turned into a board before it can be used to manufacture flooring. There are two basic processes in use.
The "solid board" method of turning round, hollow stalks of bamboo into solid, rectangular flooring planks starts with ripping bamboo stalks into strands. The waxy outer skin and any nodes are removed. The strands are soaked in boric acid or a lime solution to dissolve starches and sugars. After drying in a kiln, the strands are glued and pressed together to form a board.
The pattern in which the bamboo strands are glued together affects the appearance of the flooring. The two common patterns are horizontal and vertical. Vertical grain flooring has more figure and can be given interesting variety by using different colored strips to simulate strong grained material. Horizontal grain flooring looks more like low-figured wood such as birch or maple.
In a second method called the "woven strand process," the bamboo is sliced into thin strips. The strands are soaked in boric acid or a lime solution. Multiple layers or plies of strips are laid criss-cross until the desired thickness is reached, then compressed under heat with a binder to form a block of bamboo "lumber" about the size of a railroad tie. The block is sliced into boards of the designed flooring width (typically 1-1/2" to 12") and thickness (3/8" to 3/4").
The final step in either process is to mill the tongue and grove that characterizes traditional strip and plank flooring.
Stranded bamboo is much harder than boards produced by the solid process, up to 2.5 times harder than red oak – the standard for North American wood flooring. Sold bamboo has more of a traditional wood look. Stranded bamboo is closer to plywood in both composition and appearance.
The majority of bamboo flooring is made in China where suitable bamboo grows in abundance. Most of the flooring imported into the U.S. and Canada at present is certified sustainable by the Forest Stewardship Council® or by the Sustainable Agriculture Network. By "most", we mean that there is still some uncertified flooring being imported, so look specifically for the appropriate certification when you buy the material.
Bamboo floors can be refinished, but it is not a job for an amateur. Bamboo is not wood and does not sand like wood. Sanding the floor in preparation for refinishing can result in a fuzzy surface as individual fibers are torn off by the sanding process. Sanding may also release undesirable chemicals, like formaldehyde. Be certain that that the flooring is not what is called "engineered bamboo" which is a thin veneer of bamboo over a plywood backing. These cannot usually be sanded without sanding through the veneer.
Like hardwood flooring, bamboo is rarely removed and replaced. It is a 200-year flooring material with proper care and occasional refinishing. If in good condition, however, it can be reused as flooring and is usually a welcome donation by ReStore or Habitat for Humanity.
Flooring that cannot be reused is bio-degradable in a landfill.
Even though bamboo is not a wood, it is a forest product and the FSC certifies it for sustainability. VOCs can be a problem with the product. Since most bamboo flooring is sold in North America and Europe, and both continents are increasingly concerned with VOCs, manufacturers have started switching to low- and zero-VOC binders. Look for certification to the Greenguard program by Underwriters Laboratory (UL). Greenguard products meet the very strict low-emission standards of UL 2818 Greenguard Standard for Building Materials, Finishes and Furnishings.
Ceramic and Porcelain File
Ceramic and porcelain tiles are made out of dirt – literally. The main component of the tile is clay. Not just any clay, however. Clay used to produce ceramics contains a high proportion of a mineral called kaolinite, and, for that reason is often called kaolin clay or just kaolin. Kaolin results from the chemical decay of silica minerals, mostly feldspar.
The clay and additives are mixed with water to produce a
slip) which is formed into a
bisque) – the body of the tile – and heated to a very high temperature (usually between 2,000° and 2,500° Fahrenheit) in a kiln using a process first discovered by early humans about 10,000 years ago.
Firing drives out water, hardens the clay and fuses the clay particles together through a process known as sintering. Note 9
It also changes the silica in the mix to a crude glass which flows into the gaps between the clay particles, sealing them up. This process is known as vitrification. Note 10 If all of the gaps in the tile are filled with glass, the tile is considered highly vitrified and becomes essentially waterproof.
How much of the mix is vitrified depends on how long and how hot the bisque is fired. If fired for a long time at a high temperature more water is driven out and more sintering and vitrification occurs resulting in a denser, harder tile more resistant to water absorption.
All clay tiles are made the same way. There is no particularly noteworthy difference between porcelain tile and ceramic tile, although the marketing machinery of the major tile producers has tried very hard to convince consumers otherwise in order to justify the higher price of porcelain tile.
Porcelain vs Ceramic Tile For more information on the difference between porcelain and other ceramic tiles, see Porcelain vs. Ceramic Tile Is There a difference?.
The material used to make clay tiles is green enough. We cannot replace the clay we use to make tile, but we are unlikely to ever rung out of it.
The process of producing tile, however, is very energy-intensive. It includes the energy expended in mining the clay, the fuel consumed in transporting it to the manufacturing site, the manufacturing process, and the energy required to transport the tile to your kitchen. Most of the energy used to manufacture the tile, about 90%, is natural gas used to produce the heat required to dry tile bisques before firing and kiln firing. Some tiles are fired twice, once to cure the tile, and a second firing to set the glaze.
Some estimates put the total energy cost of one installed tile measuring 12" x 12" at about 6,750 kilowatts – enough energy to keep a 100 watt light bulb burning continuously for 1,875 hours.
As ceramic tile is one of our favorite flooring and countertop materials, finding that it is not as environmentally friendly as we would like is a disappointment. We will continue to use it and even recommend it for its favorable qualities, Glazed ceramic is durable, heat resistant, cannot stain, cut, or mar, and is very hard to break. In many ways, it is the ideal countertop material and one of our favorites (with cork) for kitchen and bathroom floors. IF it were only a little bit greener …
- See Plastic & Health: The Hidden Costs of a Plastic Planet, Center for International Environmental Law, 2019.
- Lumber is often referred to by environmentalists as "natural wood" to distinguish it from engineered wood products such as plywood. Lumber, however, is not natural. No tree grows lumber. Trees grow wood that has to be processed in a sawmill to become lumber.
- Urea-formaldehyde is the preferred binder due to its low cost and fast curing time which speeds production. Phenol formaldehyde, however, is more moisture resistant and preferred for exterior grade panels. It also produces less formaldehyde off-gassing.
- Manufacturers reduce the amount of off-gassing by using scavenger chemicals that capture the formaldehyde and turn it into a benign substance that has no harmful effects. The usual scavenger chemical is ammonia which reacts with the formaldehyde to produce hexamethylenetetramine, a crystalline compound used in industrial production and in medicine in the form of mandelic acid salt to treat urinary tract infections.
- According to the Directory of Nebraska Quarries, Pits, and Mines, Nebraska has 88 quarries, most of which produce limestone, a stone that underlies most of Nebraska. The quarries produce riprap (a loose stone for foundations and ballast), agri-lime (a soil amendment used in agriculture), road ballast, limestone used to make concrete, and decorative wall stone used to build retaining walls and in facings on buildings. Not one quarry, however, mines slabs for countertops.
- 1,600,000,000,000,000,000,000 metric tons.
- Tung and linseed oils are not actually approved by the FDA. They are "sanctioned" for use in food preparation per 21CFR181.26. The two terms are quite different. An approved substance requires extensive testing to prove that it is not only harmless but actually beneficial. A sanctioned substance is assumed to be harmless because it is (1) traditionally used and (2) no harmful effects have been noticed. However, it has not been tested to show that it is beneficial and harmless, an expensive and time-consuming process.
- The chemical reaction that occurs in varnish as and after the solvent evaporates prevents the varnish from being redissolved by its solvent. Other clear finishes such as shellac and lacquer cure solely through evaporation. No chemical process occurs. In consequence, even once fully cured, they can be redissolved by their respective solvents.
- Sintering is normally defined as a process of making a powdered material coalesce into a solid mass by heating it but not liquifying it. The clay particles in the bisque do not melt but do get hot enough to stick together. In metallurgy, it is a cheap and fast way of forming metal without having to cast it in liquid form. The resulting product is not nearly as strong but so-called "clinker casting" is suitable for things that do not have to be particularly strong such as cabinet knobs and light-duty hinges.
- The process of transforming a clay paste into ceramic tile through firing is one of the most complex in industrial chemistry, involving several what chemists call "structural transformations" of kaolinite and silica materials. Kaolin becomes metakaolin at about 1,100° F begins to form a material called mullite at about 2,000°. As the temperature continues to rise, silica in the paste is transformed into molten glass. Mullite and glass in its various forms are the major constituents of fired ceramics. The Kaolin clay transformed into mullite gives the tile its characteristic strength, structure, and shape while the glass helps it resist water penetration. M/li>
- "Embodied" energy is an accounting method that calculates the total energy necessary to produce a product. Embodied energy for ceramic tile includes the energy required for kaolin extraction and transportation to the manufacturing facility, the manufacturing process itself, transportation to the site where the tile is to be installed, and installation. The most widely accepted measure of embodied energy is MJ/kg (megajoules of energy needed to produce one kilogram of tile).
Translated from Junzia Peng et al.,
CO2 Emission Calculation and Reduction Options in Ceramic Tile Manufacture, Energy Procedia Vol 16, pp 467-476 (2012). Other sources estimate carbon emissions as high as 0.75 lbs. per square foot of tile produced.