Facts about Granite Slab Quality Variables

8 years ago

I am a fabricator with many years experience. I see a lot of mis-information about stone on the website so I wanted to offer some facts:

Note most of the following applies to any natural stone.

0. there are many different kinds of stone which are used in countertops. some are only slightly harder than jello and roughly as adsorbent as a sponge. Others are practically impervious to stains and only slightly softer than diamond. A good fabricator will make certain you understand the material properties of the stone you selected. (Note: Interior designers are notorious for specifying stone based on the "look" with no consideration for the stones material characteristics in the application.)

1. Slab suppliers are NOT all alike. At the quarry (in Brazil, Saudi Arabia, Russia, Denmark, or many, many other places) slabs are graded based on color, lack of fissures, lack of cracks, lack of (or presence of desirable) inclusions.
Some slab suppliers buy only 1 grade material, some buy cheaper.

2. Many stones are treated in the polishing process with a resin which is applied before polishing. This resin process fills the small pits (too small to feel with your fingertips but visible with the right lighting). This is done because the stone is more commercially valuable with the pits eliminated. The resin treatment process also makes the stone much more stain resistant.

3. the resin treatment does change the color of the slab slightly and on light colors this color difference will be evident on the edges. a quality fabricator treats the edge during the finishing process (before final polish) to make the edge color match the top.

4. Dyed stones are becoming more prevalent. The fabricator has to treat the edges during the finishing process so the edge color matches the top.

5. crappy stone is full of fissures and/or fill. fissures can be considered a natural feature of the stone but they do present challenges and limitations for the fabricator.
Fill is epoxy filler applied at the quarry to fill blowouts that occur during poliishing or sawing the slabs from the block. small fills (maybe the size of a quarter) can be tolerated in an otherwise beautiful stone. some slabs have much more fill. often the fabricator can work around fill. A good fabricator will make sure you know there is fill and where it will be in your countertops as it could easily be much more conspicious in your countertop than as part of the slab.

6. Many stones used in countertops are very stain resistant. Others, like the various limestones and marble colors, are very easily stained even when properly sealed. These stone are so porous and hydrophillic that when placed on a wet saw table the top of the stone will start showing wet spots from water wicked up thru the stone after only a few minutes.

7. some stones have material properties which preclude certain edge profiles. Others are so easily chipped that only a moderately rounded edge is advisable. Also, some stones can be rock pitched easily and on others it's almost impossible. If a fabricator calls you and says a particular edge isn't working on your stone it'snot because he doesn't want to do it; it's because the stone won't let him.

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