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I am in the process of grinding and polishing a pour-in-place concrete countertop. When I am done, I want to seal with a penetrating sealer. I don't want a surface epoxy or wax sealer. I like the look of the exposed aggregate and it looks great when I am wet-polishing it. but when it dries, it's all a very flat light-grey and the aggregate does not stand out well. I would like to darken the color of the concrete to give it that damp-wet look. Perhaps further polishing with finer-grit pads will give it more shine, but I'm curious if someone with experience here can help me decide if I need a stain or if a penetrating sealer will suffice.

The dry look I dont want (dry after 50-grit polish): enter image description here

The look I am after (slightly damp after 50-grit polish): enter image description here

If anyone is curious, the dark spots are portland cement I used to fill pits and low spots. Part of my motivation to darken the color is to make them less noticeable.

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There is a method that can solve both of your problems. I’m not sure how to translate it in English but it is called something like "polishing up to a point of black gloss“. This method makes the concrete waterproof and also brings up the color like you wanted. Back in the past this is the way people made their floors waterproof. Basically you polish concrete with something like fine sand stone till your hands start to bleed and then some more. Today you can use machines called "helicopters" which are rotating steel blades and high speed producing same effect.

  • Polishing up to 6000 grit polishing pads got me 50% there. I finally used a sealer to give me the shine I was after. – Paul May 3 '15 at 14:38

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