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Expert Answers
Is it normal for Granite Slabs to be Impregnated with Resin?
QUESTION
Is it normal for Granite Slabs to be Impregnated with Resin? - We are replacing our counter tops with granite and I was hoping I could impose upon you with a quick question. After lot of searching, we picked a granite called Golden Noir, which we had not seen elsewhere. The fabricator (whom we trust) called to say he had just done an install of the same granite and an issue had arisen because the edges are much lighter than the top. I looked at a sample that the supplier had busted off the corner of the Golden Noir slab we eventually selected. The top is definitely a different color than the sides except where it looks like lacquer or resin or something has flowed onto the side. I'm sending you three pictures that show this. Is this legit? Our fabricator seems mystified about this which strikes me as odd (why has he not seen this before?). we love the color of the granite but I'm not sure how I should feel about this particularly where we paid extra for this granite because it is "rare". I did some looking on line and it looks like dyes and stains are not ok but resin may be. Any thoughts/guidance would be appreciated.ANSWER
ANSWER - Golden Noir appears to be a Brazilian granite from what I can tell. Keep in mind that different names are sometimes given to stones to disguise it so you can't easily shop it from other suppliers. Also keep in mind that some stones may be sold as a granite, but they may not be a true granite. The only way for sure to tell is to perform a petrographic examination by a qualified geologist and to test its physical properties per ASTM C615 to see if it meets the respective minimum/maximum requirements.Many of the more colorful granites with a lot of movement in the color of the slab are more fragile. So to somewhat reinforce the slab and to enhance the color of the slab they will impregnate the slabs with a resin before they polish it. This causes the slab to be darker and more colorful. A drawback is that the edges of slab tend to be lighter. There are some products available for darkening the edges during the fabrication process, but they aren't known to be very successful in matching the surface. There is no standardized process or materials used for resin impregnation so you never know what will be compatible and what won't in terms of darkening the edge and in terms of sealing the stone afterwards.
The resin process can hide cracks or other blemishes which maybe structural flaws.
The resins are known to be vulnerable to UV light exposure and can cause color change or surface degradation.
All that said, it is very common today to have slabs of stone impregnated with resin. It doesn't really affect the life of the material. You do want to make sure the granite doesn't absorb or is sensitive to acidic foods and drinks or doesn't scratch easily. True granites do not.
If the supplier is saying it is a true granite then ask them for supporting documentation and a letter that says it meets the ASTM C615 physical properties for Granite, and that it is suitable for your intended use.
If it were practical for you situation, we could provide the testing of the material to help you determine if it is suitable for the intended application. Click on CTaSC Testing for more information.
