Focus on the Countertop: Corian versus Silestone

…or Zodiaq, Cesarstone, Granyte, Granirex, Zylstone, Hi-Macs, Volcanics…

So what is the difference between Corian and Silestone? Well, very little — or quite a bit — depends on who you ask. We’ll just give you the facts, and let you decide.

Backgrounder: Solid Resin Countertops

In the 1960s the E.I. du Pont de Nemours company — commonly called Dupont — was attempting to find a solid surface countertop material to market to hospitals and homeowners. It needed to resemble marble, be damage and stain resistant, and moldable in a few basic colors. Something that would “out-marble” marble. They introduced “synthetic marble” made of polymethyl methacrylate in 1967. It was offered in three basic shades of white and beige, and Dupont called itĀ Corian.

So what is Polymethyl methacrylate? (You may want to skip to the next paragraph unless you are a bonafide egghead) “PMMA” is an acrylic based thermoplastic. A chemical reaction between acetone and hydrogen cyanide results in acetone cyanohydrin. This is heated with methanol and sulfuric acid and becomes a monomer called methyl methacrylate monomer or “MMA.” It becomes a polymer via free radical process using peroxides. It may be modified with things like butadiene, vinyl, and whatnot, but Dupont ain’t about to give away the recipe for a cash cow like Corian.

The resulting resin — resin is simply what the trade calls unprocessed plastic — is in the form of small beads or pellets. It then must be processed; either cast, extruded, or injection molded. As the raw plastic is processed, colorants are added, and DuPont states that “minerals” are added to Corian as well. Most solid surface countertops are cast in sheet form, a process in which the MMA is polymerized with peroxide between two glass forms under heat and pressure.

In short, solid surface countertops like CorianĀ® are plastic — as plastic as that keyboard in front of you, or the shampoo bottle you use, or your cel phone. Other solid surfaces, such as Hi-Mac, Volcanic, etc. are similar. Virtually anything called a “resin” countertop is based on polymethyl methacrylate; each manufacturer varies the recipe, heating and reaction times, and additives to achieve whatever their blend happens to be. It is a difficult process to do correctly; too much heat creates air pockets in the casting process and ruins color.

In the early days, Dupont used a two-step process to form Corian. Technological advances now enable it to be made in a single casting, which is why the pricing has actually decreased when compared to the rate of inflation. Color availability has increased through the years; what started as 3 became 18 and is now over 80. According to the company, white remains the most popular. Competitors have entered the field as well, and that probably has something to do with the pricing. The fact that neither granite nor engineered stone are available in a true “white” color partially explains why white Corian sells so well. If you want a white, solid, stone-like countertop, you need to look to the acrylic type.

Regardless of the manufacturer, solid resin countertops require precise chemical processing and tightly controlled casting. It is not something you’ll see on every street corner. Oddly enough, many of the large plastics processors who produce solid resin countertops also produce the laminates for laminated “Formica” type countertops.

Backgrounder: Engineered Stone Countertops

The increased popularity and availability of solid stone countertops has put a bit of a dent into the business that was virtually monopolized by giant plastics companies for decades. It only makes sense that the plastics companies would want to fight back, and indeed they are: Engineered Stone. Almost every company that sells solid resin countertops now offers engineered stone countertops as well. Dupont’s Zodiaq (once known as Granirex) is offered as an alternative to Corian for consumers who want a “real” stone surface.

But engineered stone wasn’t created by the plastics people. Imagine if you owned a quarry full of quartz. Nice looking stuff, but you can’t cut it in slabs like you can cut other rocks, such as granite or gneiss or marble. Or perhaps you have a quarry full of very brittle granite. You try to mine it, but you just wind up with crumbly bits of feldspar, quartz, mica, or whatever happens to be in your local version of granite.

Your quarry just won’t produce slab, but over the years you’ve found creative ways to sell your grit and chips just the same. Surely you can figure out a way to make it solid…

A man named Marcello Toncelli of Treviso, Italy did just that in 1977. His company, Breton Spa, developed a way to make solid block out of the crumbly rock found throughout Italy’s Dolomite Mountain region. By mixing 94% stone particulate and 6% plastic (usually polyester) to hold it together — plus some undisclosed additives — then using a patented ?vacuum vibrocompression process,? Toncelli successfully developed plastic rock. Or, more appropriately, rock plastic. The resulting product was offered as a kitchen countertop material under the brand name Bretonstone.

The technology was quickly embraced by Grupo Cosentino, a large minerals firm in Spain. They too had a lot of semi-useless crumbly rock in some of their operations, and began aggressively marketing their Silestone product around the world. A host of other brands have popped up; Cesarstone, Granyte, Avanza, and so on. Zodiaq is the engineered stone countertop Dupont offers as an alternative to Corian.

Breton Spa’s process is not nearly as complex as the chemical processing required to make Corian, and they’ll sell their vacuum vibro whatever-it-is to any interested quarry or mineral processor. So virtually all of the engineered stone countertops are made the same way, except for the German brand Cristalite, which is granite chips cast in acrylic.

The idea of mixing semi-useless material with plastic to make a useful surface isn’t limited to stone. If you do a little more shopping, you’ll find kitchen countertops made of recycled aluminum chips bonded with plastic, and who knows what else. Whether it’s granite chips, quartz chips (a component of many granites), dolomite, gneiss (a lot of granite countertops are actually gneiss, but it really doesn’t matter), feldspar (a component of many granites), marble, silicates, igneous stone, or recycled aluminum, Engineered Stone is particulate matter held together with resin.

Plastics — The Common Thread

“Resin”…that magic word that sounds so wonderful…remember that it simply means “plastic.” Ask anyone in the plastics industry to explain the difference between resin and plastic and they’ll probably look at you a little strangely, and say something like, “resin is plastic, it’s the plastic pellets we put in the molding machine.” And whether you zero in on Corian or Silestone or some derivative thereof, plastics are the key.

Plastics are so pervasive in our lives, yet most of us are unaware of it. Whether molded as a solid, foam, sheet, fabric, or elastomer, you live in a plastic world. By volume, most of your car is plastics. Your computer, your desk at work, digital camera, television, telephone, pen, hair dryer, clothing, pen, furniture cushions, electrical sockets, billiard balls, the vinyl on a loose-leaf binder, contact lenses, boats, even the Teflon (Dupont) coating on your cookware, all plastics. Yet for some reason, we balk at the concept of plastic kitchen countertops. Your sales representative may not even know that the material in Corian or the binder in Silestone is plastic. Ask, and you’ll likely be told, “no, it’s resin,” or “it’s engineered acrylic.” You can safely assume that they aren’t intentionally trying to mislead you — just that they are unaware of precisely how their product is made. On the other hand, your salesman may openly agree that it is indeed plastic, which indicates that their overall product knowledge is probably fairly reliable.

The point is, both types of materials derive their formability, strength, ease of cutting and fabricating, stain resistance, and other mechanical properties from the “plastic” aspect of the mix. So when you boil it all down, even though the primary component of Silestone is indeed stone, the fact is that Corian and Silestone are very similar solid surface materials.

A Few Differences

Solid resin like Corian has a bit more versatility in terms of how it can be formed, the sorts of inlays that can easily be added, etc. It is also supposedly easier to repair. And although both can be fabricated easily, at the end of the day it is likely that solid resin materials will be more “seamless.”

Engineered stone like Silestone is obviously more “stone-like,” simply because it is 94% stone or mineral product. It is possibly more heat resistant, and somewhat more scratch-resistant.

Understand that in whatever areas one material offers superior performance, it is not by a wide margin. And in every case, you can find experienced installers who will disagree with these statements. So the differences, whatever they may be, are largely ones of perception.

When you get to the bottom of it all, the primary difference is visual…

Visual Differences

Visually, both materials have their proponents. Probably the best way to “contrast” the two is to say that, by nature of how it is made, engineered stone looks more like granite and solid resin looks more like marble.

Why engineered stone looks like granite: Natural granite is a few types of stone (usually quartz, feldspar, maybe mica) and a stone binder, all “glued” together by pressure and heat. Engineered stone simply uses smaller bits of rock, and replaces the stone binder with plastic. Granite is made by heat and pressure deep in the earth; engineered stone is made by heat and pressure via the “vacuum vibrocompression process.” Thus engineered stone resembles the natural granite it emulates.

Why solid resins look like marble: Marble begins as limestone that “recrystallizes” due to heat and pressure. Other minerals present in the limestone during recrystallization affects the appearance and color of the marble that forms. Solid surface begins as a monomer that melts and “recrystallizes” due to heat and pressure. Other materials present in the plastic during recystallization affects the appearance and color of the acrylic that forms. Marble is made by heat and pressure deep in the earth; acrylic is made by heat and pressure via the plastic casting process. Thus solid surface resembles the natural marble it emulates.

Which “look” do you prefer?

— Rick Bolger

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Some Concepts to Keep in Mind…

Have nothing in your house that you do not know to be useful or believe to be beautiful.

— William Morris, circa 1870

We have planned houses from the first that are based on the big fundamental principles of honesty, simplicity, and usefulness — the kind of houses that children will rejoice all their lives to remember as “home,” and that give a sense of peace and comfort to the tired men who go back to them when the day’s work is done.

— Gustav Stickley, circa 1910

…of all reforms needed in the life of the home, that of the relation of the man to his family is most pressing. Modern materialism demands of far too many men an unworthy sacrifice…A simpler standard of living will give him more time for art and culture, more time for his family, more time to live.

— Charles Keeler, circa 1905

Do not think that simplicity means something like the side of a barn, but rather something with a graceful sense of beauty in its utility from which discord and all that is meaningless has been eliminated.

— Frank Lloyd Wright, circa 1908

Our preoccupation with material success threatens to blind us to the value of the patient, honest cultivation of mind and character.

–David Saville Muzzey, Prof. of History, Columbia University, circa 1929