Thursday, November 30, 2006

Grades of Granite

I hear and read so much garbage about 'grades' of Granite.

Let me expound a bit on this subject. There is no universal grading system for Granite. Each individual factory makes their own determinations about what is First, Second, or in some cases 'Commercial' grade. Ideally, when a factory owner cuts a block of say Santa Cecelia, they know what they expect it to look like. These people are very sophisticated at what they do. This is not happenstance. I had factory owners showing me blocks that they knew were going to yield 2nd choice or commercial grade. Sometimes, they are surprised, but not usually.

Virtually all Brazilian factories 'resinate' their slabs. This is a different, yet related, subject. If the Santa Cecelia, which is supposed to be pale yellow with black and gray, with garnets and a gentle flow, somehow has a football sized black spot in the middle of it, it will be termed 2nd choice, or perhaps even commercial. Structurally, is it inferior? No. It is a color flaw only. It will 'perform' no differently. As a fabricator, I'll cut around that spot. As a distributor, they can't buy materials like that because the normal fabricator will jump up and down about the spot.

Now, I'm not saying that all US distributors ignore 2nd and 3rd choice stones. Because, I know first hand that they buy 2nds and 3rds all day long. There are some materials, like Boreal or Key West Gold, that are infamous for having blue spots in them. Depending on the size and location, they may be graded from 1-3. Is there any structural problem? No. The problem I have with some distributors is that they'll buy what I know are clearly second choice stones and then charge A grade prices. There are four that service this area that are famous for that.

To summarize, there are about 4 primary reasons why a slab may be downgraded. Spots, coloration, fissures or cracks, and pocked surfaces. Fissures and filled cracks [with epoxy resin by the factory] are a part of some stones. You know they are going to be there. Most factories are good at filling voids, but some are not. These can certainly downgrade a stone. But, frankly, we can fix even a bad patch job by the factory.

Now, pocked surfaces are a problem. Can we fix them? It depends. It is a function of time. Do you want to devote one employee for 8 hours to try and salvage a slab of Tropical Brown? The math is not favorable for that. When we or our agents examine stone, one of the first things we'll do is look at the surface 'down light'. That is where the pits or pocks will be noticable. Tropical Brown and Baltic Brown are two to examine closely.

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This is Golden Shadow, 2nd choice. In all likelyhood, this is probably New Lapidus. Different factories use different names. Note the color change from the top portion to the bottom section. That is why this was a '2nd choice' stone.

Therefore, 'grades' are in the eye of the beholder. If it is pleasing to your eye, and some little Brazilian inspector deemed it 2nd choice, so what? If you like it, that's the bottom line.

9 comments:

rod said...

I have considerable experience as a production quarryman,scaler,grader, and granite exploration consultant. I currently own and operate a marble & granite fabrication shop and stone restoration business. Granite quarries do have a grading system which differs somewhat from primary processors, distributors, and fabricators. There are 4 grades at the quarry level.
A- Monumental/Sculpture grade. Homogenous in color or consistently variegated. Grain will be ideally exposed when processed and surface polishing will close up well. Larger block yields,free of embedded fractures or surface fissures. Rift & Grain are ideally factored. Structurally sound.
B- Building grade. No consistencies in grain and coloring. Blocks are large but may contain fractures which are considered workable within processing machinery tolerances. Stone may be quarried with alternative grain structure.
Structurally sound when processed.
C- Utility grade. Usually smaller blocks with numerous fractures and fissures. Can be split or sawn dimensionally. Surface finishing limitations as well as structural limitations.
D- Waste/Landscape grade. Generally used in the quarry for road building or sold as landscaping material.

Chris Amstutz said...

You have a great blog for granite and I've linked to this post which I find very educational. Hope you don't mind I post a back link..

Chris

www.WeNeedRehab.com

Elaine said...

I have just had a piece of granite put in my bathroom which looks fantastic, but I can't believe how much water it is soaking up. If I put a cloth down or a container, or if there are splashes from the basin they leave a dark spot within a minute or 2. Have the suppliers given me marble instead of granite, or is this a lower grade of granite? Any info would be appreciated.

rod said...

Elaine, most granites and marbles require either a penetrating sealer, a top-coat sealer or both, depending on the stone's minerology. There are thousands of varieties of granites and marbles available not including the differences between each slab of stone from the same origin. I recommend a fundamental approach which when properly applied will for most stone countertops cause water to bead on the surface instead of penetrating and forming dark spots. Not only will this prevent water absorption but also staining from generic household cleaners, cosmetics, organic compounds, etc. Home Depot and most tile suppliers carry a few product brands such as: "Stone Specific", "Tile Lab", "Stone Tech". They all produce a penetrating sealer for polished granite which is also very effective on polished marble. Penetrating sealers soak into the stone and work below the surface. This provides long lasting protection and differs from top coat sealers which are more susceptible to wear factors. Let's begin... It is important to clean the granite surface and dry it completely before applying the penetrating sealer. Home Depot carries cleaning solutions for granite and marble to be used prior to sealing. These are usually mild to neutral ph cleaners that do not contain additives such as waxes which would prevent the sealer from penetrating. Alternatively, a strong solution of water with either pickling vinegar or baking soda will also work effectively. Rinse well and allow the granite to dry completely. I sometimes facilitate this with a strong hair dryer or heat gun. Wear gloves and eye protection and apply the sealer using a thickly folded paper towel or a disposable clean white cloth. Make sure to saturate the towel well so that a generous amount of sealer is applied. Try to avoid depositing sealer on mirrors, sinks faucets, and wall areas. The stone's surface should look completely wet and will dry fairly quickly as the sealer penetrates and evaporates. This process usually takes between 10 to 15 minutes. Apply a second coat and allow this to dry for the same amount of time. Be ready to buff the surface with a dry terry or microfibre cloth as it is easiest to remove within this time frame. The amount of residue left on the surface will depend on the porosity of the stone its absorption rate. In either scenario your stone will be adequately sealed. Stubborn residue is easily removed using a piece of extra fine steel wool which may also be used periodically to maintain your granite's luster. Steel wool leaves small filings behind which wipe up easily with a slightly damp cloth. Home Depot carries a cleaning products brand called "ZEP" which produces a spray-on wax based cleaner for granite countertops. This or a similar product designed for granite will provide an additional protective barrier, enhance your granite's luster, and make day to day cleaning streak- free and almost enjoyable. I re-seal my granite countertops every 1-2 years. Sink and cooktop areas; 6 month-1 year intervals for maximum protection. Best of luck!

royalandcrowned said...

hello rob, we are about to have granite countertops installed and the slab that we have chosen is silver cream. In my tedious search, i finally found a site that stated silver cream is a high grade granite, i was also told by a sales person that it is also an exotic slab. First question, is all of this true, and if so, what would be a fair asking price per sq foot. thanks for all of your help. I am located in Florida, if that makes a difference.

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Gexton said...

Thanks, you guys that is a great explanation. keep up the good work in your blog.
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Unknown said...

Thank you for your information on the various grades of granite. I just got a solid granite shower pan that is grade A but I could not find a clear description of what grade A means until I came across your blog post.