This is happening to me with Thunder White! I have new build I've been in less than 3 months. The stone contractors are coming this week. I will post photos later.

Some lighter natural stones are notorious for staining. Try some Tenax Pro Seal and hope for the best please.

Thank you Joseph. My fabricator is coming Thursday to 'dry it out' and reseal. I've noted on reviews online that Tenax seems to be the best. Which version do you recommend? Note that this Thunder White stone also seems to be sensitive to oil stains.

Great question Mary P. and one we hear often. Granite is a natural stone which is great choice for countertops. However, being natural there are no two stones exactly alike. Some granite is more porous than others. When natural stone turns dark, it is usually from a liquid penetrating into the stone. It could be water, which will evaporate or it could be a liquid or substance with color which when dried, leaves a stain. The staining is why it is preferable to be proactive on stones that darken with water by applying a sealer. But what is a sealer and how do know what kind or how to apply, you may ask?

Sealers are confusing as most people view sealers as a topical barrier which when cured produces barrier preventing anything from entering the stone. Topical sealers actually cures as a film on the surface of the stone producing a topical protection. We do not recommend this type of sealer, for many reasons. Topical sealers, are softer than the stone which shows scratches and wear and more importantly affects the beautiful luster of the stones finish.

So we highly recommend an impregnating sealer or often referred to as a penetrating sealer. These sealers penetrate into the stone soaking into the porous spaces between the minerals making up the stone. Depending on the density of the stone will determine how far the sealer will penetrate and how much sealer will be needed to produce the desired result. This type of sealer is actually designed as a repellant thus the confusion. The impregnating sealer (depending on the make up of the sealer) either repels water (hydrophobic) or water and oil (oleophobic) which is preferred for countertops. This type of sealer cures below the surface of the stone minimizing the ability for liquids to penetrate. This type of sealer "helps" prevent staining. Notice the word helps. Since it is not a barrier, it is not a 100% stain proof. Many reasons for this including the level of care given after application. See link at bottom of page.

With all that said, somewhere between the quarry and fabricator some impregnating sealer has likely been applied. Not always but usually. The question is how well? Based on your observation that the stone darkens when wet, I would expect that the stone needs additional applications of sealer. This can easily be done by applying a quality impregnating/penetrating sealer to rejection. Follow directions on the product is best but we apply the product on the surface, gently agitating the sealer to help break surface tension and allow to sit on the surface until no more sealer penetrates. As is soaks into the stone, add more until it is allowed to sit on the surface as long as indicated on the product label. Then wipe of the remaining sealer and using a microfiber towel, hand buff the counters. It may be necessary to reapply per directions on the product or by determining the need based on the darkening on the stone a day or two later. Eventually the pores in the stone will be filled with product and you will then find you have maximum repellency.

I will not get into the discussion of what sealer is best as my testing is that there are many quality brands and actual results may vary based on the nature of the stone as well as quality of application. Just make sure the countertop is clean and dry before applying sealer. Make sure there are no stains and if there are, remove before applying sealer. Refer to article link below.

For care of your stone, perhaps the Natural Stone Institute information here will be of value: Care of Stone

I hope this helps!

I am a fabricator. Natural stone is porous to varying degrees depending on the type of stone. Sealer greatly reduces the absorption rate of stone but it does not make it waterproof. A wetting or staining agent left in place over time will still get into the stone. A good sealer gives you time to remove the liquid before it gets into the stone. (I once came home from a day at the lake and left a soft pack cooler full of melting ice on the countertop overnite. Had a huge dark spot the next morning but as expected it disappeared over several days as the stone dried out.) You can reseal but if your expectation is waterproof stone you are likely to be disappointed.

My fabricators just left after sealing my Thunder White granite with Tenax Proseal. Let's see how this goes.