So what choices do I have for a concrete sealer for concrete countertops, and why do I even have to think about it? Because concrete is naturally porous, it'll darken when it gets wet. Anything liquid will be sucked right into it unless a sealer blocks it. Water isn't so much of a problem; when it dries, the concrete reverts to its original state. The problem is when other liquids like vinegar, lime juice, or mustard are spilled on an unsealed surface. These can actually "etch" the surface of the concrete and damage it. Sealing the concrete can help to prevent this problem, depending on what type of sealer you choose.
A Concrete sealer for concrete countertops can be broken down into two camps: water based and solvent based. They're pretty easy to tell apart just from appearance and smell. Water based sealers tend to be milky white and have a low odor. Solvent based concrete sealers are almost always completely transparent or have a slight yellowish tint and have a strong odor. To make things more confusing, sealers can also be categorized as topical or penetrating. Topical sealers form a "skin" on top of the concrete, sealing it from liquids, while penetrating sealers are absorbed into the concrete and try to do the same by sealing the small concrete pores internally.
So is one better than the other? As always, it really depends on what you are planning to do with your countertops. If stain resistance is your number one priority, the best concrete sealer for concrete countertops is going to be a topical sealer. As these are applied over the concrete, they tend to prevent liquids from penetrating into the concrete, though different types of sealers offer different levels of protection (more on that on the next page). Depending on the type you select (epoxy, polyurethane, or acrylic), it can change the final appearance of the countertop, as it will if you choose between a water based sealer, which tends to have a more matte, satin finish versus a solvent based sealer, which generally has a high gloss finish that darkens the concrete color (think of it like pouring water on a concrete floor; it gets a glossy, darker look).
If a more natural appearance is your number one concern and you want complete liberty to cut and put extremely hot pans on them, then the best concrete sealer for concrete countertops is going to be a penetrating sealer. These do not leave any kind of film on the surface; they work by penetrating into the concrete and sealing the capillaries and pores in the concrete itself. That means hot objects, knives, etc. won't damage the sealer, as it is not on top (that doesn't mean you can't scratch the concrete itself, but that takes a little more work). Penetrating sealers have almost no effect on color or appearance, but they are not as effective at stain resistance as the topical sealers. That means that wine, lemon juice, milk, and other foods can stain the countertops pretty fast if you are not diligent in wiping them up when spills happen.
There is no perfect sealer, but when given a choice, most clients prefer to go with the topical sealer as it offers the best of both worlds-good stain resistance and good resistance to heat and other normal situations found in a kitchen or bathroom environment. Let's talk a little more about which type of concrete sealer for concrete countertops you should consider in the next page. Keep in mind that no countertop made of granite, marble, Corian, Silestone, or Formica is 100% stain proof.