Note: Do not attempt to polish concrete that has cured for less than 12 days.
Polishing your concrete countertop is no different than grinding it. Polishing uses diamond grinding pads that are finer than 800 grit, and finishing with 1,500 grit or even finer.
Use the same techniques as described in the aforementioned grinding section. Namely grind, squeegee the water and grit off the concrete countertop until you are satisfied with the finished product.
Note: A piece of concrete polished with a 1,500 grit diamond pad will feel smooth to the touch and still provide ample roughness to hold a topical sealer. Many professional countertop manufacturers will use much finer pads and polishing compounds to produce a very shiny surface. You can continue on with finer pads, if you so desire, however we do not think that it is necessary.
Note: Use diamond hand pads to get into the inside corners of the hole for the sink.
Sealing your concrete countertop
Warning: The following information is applicable to residential countertops. If you are building a concrete countertop for a restaurant or other commercial food processing facility check with your local building department as there may be specific codes applicable to what finishes and sealants can be used.
Concrete is actually a porous material and will stain, especially if citrus juice, vinegar or wine is spilled on the surface. Because it is porous it should be sealed to protect the surface and to prevent bacteria from growing in the pores of the concrete.
First, we will discuss the different types of concrete countertop sealers then we will give you are sealing recommendation.
Note: The entire sealing process which includes using a sealer, mineral oil and wax can all be accomplished in the workshop prior to installing the countertop on the kitchen base cabinets and that is the way it is explained. However, you can do part of the process in the workshop, applying the sealer and then apply the mineral oil and wax after installation in the kitchen. We prefer to apply the mineral oil and wax after the countertop is installed in the kitchen because the piece of concrete is not as slippery without the mineral oil and wax applied, which we feel, makes it easier to carry the pieces to their final resting spots.
There are two categories of concrete sealers that can be used:
- Topical sealers
- Penetrating sealers
A topical sealer is the category of sealers that place a film over the countertop; similar to placing a sheet of plastic wrap on the countertop to protect it from staining if liquids are spilled on it. However, there are some disadvantages in using topical sealers. A hot pan or pot placed on the surface will leave a scorch mark, as well, topical sealers have a tendency to lift off the counter and if there is a lot of countertop activity the topical sealer will have to be removed and replaced every few years, which in itself is a complex project. For those reasons, in our point of view, is the primary negative to using a topical sealer, it makes the countertop appear to be encased in plastic.
Topical sealers include most of the acrylic and lacquer based products including urethane and epoxy resins.
If staining is a major concern for you or your better half, then the use of a topical sealer is probably the sealing product you should choose. If this is for a kitchen countertop, you should choose a sealer such as Glaze 'N Seal, as it can be used in food preparation areas without concern that the product will contaminate food.
Penetrating sealers, both solvent and water based, do not sit on the surface of the concrete countertop they penetrate the top layer of the concrete to provide the protection and are invisible to the naked eye. Citrus juice and wine spills, if not wiped up very quickly will etch the surface of the concrete countertop; making it rough to the touch. However, the advantage is that hot pots and pans placed on a concrete surface with a penetrating sealer will not leave a scorch mark and because there is no apparent covering on the surface of the concrete, it will not scratch.
Note: Penetrating sealers are much easier to apply and maintain than topical sealers.
Concrete countertop sealing recommendation
We recommend that you use a water based penetrating sealer for a concrete countertop that will be used in a kitchen with a top coating of carnauba wax.
Continued - How to apply sealer to concrete countertops
How to Make Concrete Countertops - Index