Are natural stone counters still natural by the time they reach your kitchen?

Published by Ben on May 02, 2012

Tags: countertops, home improvements, natural stone, Sustainability

'Natural stone' and created by ‘Mother Nature’ are just two of the ways I’ve heard granite and marble counters described.

As explained in excerpts from an article in the magazine Stone World, it goes through a considerable process before it is prepared for use in your kitchen or bathrooms.

Natural stone comes in many different colors, shapes and textures. A lot of these materials unfortunately have natural defects, mostly fractures and superficial holes and pits.

In marble polishing, the use of polyester resin to fill and reinforce the slabs has been an accepted solution for over 50 years.

Nowadays there are many different kinds of polyester resins, with different viscosity, color and hardening times. Some resins have even the capability of UV hardening, allowing a very fast curing time.

Generally, the systems commonly used in marble processing are not satisfactory for granite processing lines. The main reasons for this lie in the different chemical structures of the two materials. Granite is much harder, with microscopic fissures and a different absorption rate. The very thin cracks represent an additional problem, since no polyester resin would have the capability to deeply penetrate in the stone, harden up and give a sufficient strength to the material.

About 20 years ago, after some unsuccessful trials with polyester and acrylic products, a new family of products was tested. Using materials with optimum adhesion (epoxy systems) on granite, the typical problems were resolved and a new technology was developed.

The epoxy resin has shown the capability to run into each of the cracks and fill all of the pits and micro-fissures present in the granite. Additionally, its long hardening time allows the glue to penetrate deeply into the stone before the complete curing will occur.

Before being treated, the surface of a granite slab has to be honed; to allow the surface of the material to evenly absorb the resin. The material also needs to be completely clean and dry, so the resin can deeply penetrate in the smallest cracks of the surface.

This process requires special convection ovens or two to three days in favorable dry working conditions. After being mixed in the right ratio (either using a scale or an automatic mixing dispenser), the resin is then spread on the whole surface.

Nowadays, there are hundreds of different epoxy systems for granite, with different physical characteristics. The right system is always chosen in relation to the color of the granite, the machinery available and the desired results to be obtained.

After the system is completely cured (usually it takes up to 24 hours, depending on the system and the equipment used) the slab is ready to be polished.

One of the first noticeable effects of the resin is a darkening effect on the whole surface of the slab. This is due to the effect of the resin on the quartz itself. This by-product enhances the color of the slab and allows for a better polishing effect as a final result.

One of the first questions that come with a resin-cured granite slab is how to match the color between the "darkened" surface of the slab and the subsequent polished edge of a finished product (like a kitchen countertop).

There are special products on the market for enhancing the color of granite and marble. Applying these products will allow you to permanently match the two colors with one application. Beware, though, of easy solutions such as mineral oil or a cheap color enhancer. These products will solve the problem only momentary, eventually leaving the customers dissatisfied in the long run.

Another issue is the durability of the process. The epoxy resin was invented in the early 1940s to develop a strong and durable product in the aeronautical engineering. The historical data available today refers only to that particular branch of the industry, while in the stone industry there are only laboratory tests to support the long-term effect and durability. So far, none of these tests have proven that the system cannot last for a long time.

Another question is whether the epoxy resin is safe for kitchen countertop surfaces, and whether they will be damaged if a homeowner were to place a hot item on the surface. The answer is that the resin materials used must comply with the latest FDA rules for food contact. As far as high temperature goes, the epoxy system has the tendency to soften up in presence of high temperatures. However, unless there is a particularly large hole that was repaired with the epoxy system, the small fractures are not affected by the local application of heat. Even if there is a large patch of epoxy glue visible, it will go back to its original status as soon as the temperature goes back down to a normal level.

Although the epoxy resining of the granite slabs has been scrutinized by the "purists" in this business, it has grown now to a point where it is not only accepted by the majority of the operators, but often required in a lot of materials. The resin has the double effect of assuring the strength of the slabs and providing a clean feeling of touch to the homeowners and other end final users.

Technology has recently improved the quality of these systems, ensuring a better natural product at a marginal cost in the final outcome. And as a result, some of the world's most beautiful granites are available on a larger scale and at a reduced cost, allowing the stone industry to deal with quality products virtually free of defect.

This is according to Stone World the leading news source serving the international stone industry since its inception in 1984.

Anything that touches food (or touches something that touches food) may be an Indirect Food Additive. The U.S. FDA requirements regarding the use of Indirect Food Additives are known as "Food Contact Substance" (FCS) regulations. Examples of FCS products may include:

  • Food Packaging, Cookware, Tableware, etc.

  • Food Processing Equipment, Production Aids, Sanitizers, etc.

  • Chemicals used as Adhesives, Lubricants, Coatings, etc.

Calling a product ‘natural’ has certain inferences also, likening it to being ‘green’ or 'sustainable' or even 'Healthy'. These terms having a difficult job being understood, these days.

Andrew Pace is the Creator of 'Degree of Green' and the 'Green Design Center' and as he explains, there are over 40 reasons why a product or service can be called green. Natural, biodegradable, recycled, energy efficient, healthy, and on. All of these fall into one of three categories: Human Friendly, Sustainable, and Environmentally Friendly. It is my belief that no single product in the building industry is perfect in all three categories. For every pro, there is a con. So, when choosing materials for customers, we must decide which of these three Degree's is most important. Essentially, that's what the Degree of Green® is all about. We educate the dealers, contractors and design professionals about this, and then they can provide assistance to the customers, without prejudice or green washing. 

My opinion about the other tops mentioned are: 

Quartz. No sealer required, easy maintenance, essentially non-toxic itself (except the versions treated with Microban). 

Solid Surfaces (Corian, Gibraltar etc)...same as above, although, the useful lifespan can far exceed hundreds of years, thus we can make a great argument for sustainability. 

Granite shouldn't be used in commercial kitchens because it’s a porous stone that can harbor bacteria. Sealers that are used for residential granite tops can either be a penetrating silicone/silicate product or a surface cured top coat. Both have their pros and cons...There is no perfect product. 

The green building industry is all about doing the right thing, unless it goes against our design tastes or aesthetic intent. When push comes to shove, we usually lean to the side of looks, rather than health or environment. Sometimes, we need to choose materials that may not be the best looking, but may better meet the customer's demands and their personal Degree of Green®.

Summing up, without question granite is varied, beautiful and has the most wow factor of any kitchen counter top material. But by the time it reaches your kitchen counter it is far removed from being natural. Considering the mining, logistics, processing, fabricating and the very thing that brings out the final polish, it’s about as natural as a hunters trophy (preserved with resins) and hung on the wall.  


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