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How to Reseal Concrete Countertops

If you want to reseal concrete countertops or refurbish old concrete countertops, it is important to understand the difference between applying concrete countertop sealer to bare concrete and applying it to previously sealed concrete.

Like all concrete countertop sealers, CCI’s sealers Omega and Ovation are designed for application to clean, previously unsealed concrete that has been sufficiently cured and has a properly prepared surface. Surface preparation is critical to success with concrete countertop sealers.

Applying sealer over existing concrete that has already been sealed with an unknown product and that may have been stained can be risky. In some cases, the existing concrete may have been sealed with a product that can prevent Omega/Ovation from achieving a good bond with the concrete.

While concrete countertop sealer adheres very well to clean, unsealed, and properly prepared concrete, it may not adhere to a surface that has been treated with a stone or tile repellant, a penetrating sealer/treatment, wax, a concrete hardener, or to concrete that is stained with oil or grease. Such surfaces are effectively contamination that will prevent good adhesion with a new sealer. 

The most problematic old “sealers” are wax and stone/tile sealer (which is a repellant). They are difficult to remove because they penetrate into the surface of the concrete.

Commercial wax removers will strip the surface wax, but what remains in the surface micro texture can only be removed by abrasive means. Do not use solvent to dissolve the wax, as this can push the wax even deeper into the concrete. Stone and tile sealers are penetrating treatments that also can be very difficult to remove.  

The most effective means to removing wax and stone and tile sealers is to physically remove the contaminated layer concrete to reveal clean, bare concrete.Later in this article, we detail exactly how to do this. First, it is important to perform a detailed assessment of your existing concrete.

Assessing Your Old Concrete Countertop

The first step is to determine what your old concrete countertops were originally sealed with.

  • If you do not know what they were sealed with, assume the worst and use Technique 1 below, grinding down to bare concrete.
  • If the countertops were “sealed” with wax or a stone and tile sealer, you must use Technique 1.
  • If the countertops were sealed with a coating concrete countertop sealer, then proceed to step 2.

Step 2 in determining how to reseal your concrete countertops is to evaluate the condition of a previously applied coating concrete countertop sealer.

If ALL of the following are true, you can use Technique 2 below. If not, you need to use Technique 1.

  • There no signs of peeling, bubbling or delamination.
  • The sealer has not yellowed from sunlight exposure.
  • The underlying concrete is not stained.  

Techniques to Reseal Concrete Countertops

Technique 1: Get back to bare concrete.

Used for: Concrete that has been treated with a penetrating sealer, wax, repellants, or where an existing coating has been scratched, is peeling off, or otherwise damaged.

Grinding Down to Bare Concrete

The best way to ensure Omega/Ovation will adhere to your concrete is to remove all traces of any existing sealer and to mechanically remove all surface contamination by diamond honing/grinding the concrete to 100 or 200 grit. (You must wet grind – see this article to understand why.)

(This grinding technique MUST be used for wax/repellants. If you have a damaged previous coating, you can instead use chemical stripper as explained below.)

Physically grinding away the top layer of concrete removes all traces of contamination that will affect Omega/Ovation’s bond to the concrete, and it creates the optimal surface profile to ensure good adhesion.

Bear in mind that abrasive honing will change the appearance of the concrete. Polished concrete, cement-cream finishes, troweled surfaces, acid stained, dyed, or glazed concrete will no longer look the same.

Also, honing the surface will very likely open up pinholes in your concrete, and these should be filled in with cement grout before applying Omega/Ovation. See this article for how to grout to fill pinholes.

Be aware also that some penetrating treatments that react with the concrete may affect the concrete at unknown depths, so you may need to remove quite a bit of the surface in order to ensure you have eliminated all traces of the treatment.

Even then, we cannot guarantee that this technique will work. Failure to remove all traces of the previous treatment will ensure the high likelihood of any new coating peeling, Omega/Ovation included. The outcome is highly dependent upon your effort, care and diligence, and that even with good surface preparation there are no guarantees of success.

That said, removing existing sealer is not difficult or messy. You can simply damp hone the existing concrete countertop in the kitchen or bathroom using a palm sander, rolled up towels and a minimum of water.

This video shows how:

Chemically Stripping to Bare Concrete

Chemical stripping uses commercial paint stripper. Avoid citrus based strippers, because the citrus oil in the stripper can leave residue in the concrete that compromises the bond between the new sealer and the bare concrete.

Ensuring You Have Bare Concrete

Make sure that the entire surface is thoroughly ground or stripped and all traces of wax/repellant/etc. or coating sealer are completely removed. An easy test to ensure the concrete is completely bare is to apply water to the surface.

Wax, repellants and coatings will keep water from fully wetting out the concrete. Bare, uncontaminated concrete will look dark when wet with water, and any traces of old sealer remaining on the surface may cause water to bead up or keep the concrete looking lighter than when it’s free of contamination.

Technique 2: Apply over an existing, undamaged sealer

Used for: A few popular urethane-based concrete countertop sealers that have not been stained, damaged or scratched, nor have any existing adhesion failure.

Omega/Ovation have been successfully applied on top of a few popular existing urethane-based concrete countertop sealers. Some but not all finishes may be successfully overcoated, as the surface chemistry of every sealer is different and may affect the surface bond. In the cases where Omega/Ovation was successfully applied, the existing sealer had not been stained, damaged or scratched, nor did it have any existing adhesion failure.

After cleaning, the surface of the existing sealer was sanded with 320 grit sandpaper to achieve a uniform dull finish without sanding through to the base concrete. Sanding down to bare concrete would affect the appearance of the concrete, as Omega/Ovation may darken the concrete (or not) differently from the existing sealer.

Only undamaged, clean and thoroughly-sanded finishes may be considered for overcoating. All other conditions will require the existing sealer first be completely removed and then the underlying bare concrete roughened to accept Omega or Ovation, as explained in Technique 1.

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