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I recently cast a concrete countertop using melamine moulds. Overall, I'm happy with the cast slab but the colour turned out different than what I was aiming for. I was using white cement, aiming for a white-ish finish but the sand I used caused more discoloration than I expected so it ended up looking brown-ish.

I'm thinking of trying to make it much darker now and am going to try and make it a black colour. Can I use a water-based paint and let it soak into the concrete before sealing it?

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    Look into concrete stains from a masonry supplier.
    – Ecnerwal
    Jan 5 at 14:45
  • Paint may hold-up for awhile, but will eventually peal and flake off. Use an acid etching stain.
    – ojait
    Jan 5 at 15:27
  • I would use one of the fancy (expensive) epoxy-based finishes like StoneCoat or Giani; a permanent durable finish without staining or sealing. If it sucks, you can always paint over it, and it still provides a heck of a seal...
    – dandavis
    Jan 5 at 21:34
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Can you paint it? - Yes. Will you regret painting it? - Probably.

A concrete stain will get into the material and darken it, and then a concrete/stone sealer will reduce the porosity of the surface.

Paint sits on top, and in countertop service will almost certainly get scarred, scraped and generally dinged up - so repainting may be a frequent task. It's not impossible (painted countertops are not unheard of) but it is annoying (painted countertops are not common these days.)

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For longevity, you must use a concrete stain to apply color to the counter top. This usually involves acid to etch the surface followed by the stain color. It is a fairly straight forward process that can be accomplished by most DIY-ers with moderate skill levels.

The problem that you should consider pertains to health issues. This staining process is used mostly for floors not kitchen surfaces where food is prepared. There is a possibility that once the stain has been applied it (ie any chemicals in the stain) may be transferred to any food placed on the counter.

Some manufacturer's state their stain is "bio-friendly" which sounds safe, but on closer inspection of the warning label it also claims "not safe in food preparation areas". Not all stains will be unsafe. Here is one link to such a product hat uses etching.

Also take note that wear and tear will make it necessary to re-finish the surface over time. Try to find a product that is the most simple to get the color you desire, will endure in it's environment and is safe to use.

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If you're going to paint it then coat it with clear epoxy afterwards so that the finish can withstand abuse.

Since you're painting it black then it should help to mitigate the yellow tint which some reviewers are mentioning at https://www.amazon.com/Countertop-Epoxy-Resistant-Resin-Gallons/dp/B00866QSLK

I have no experience with these products so if it's tintable then I would opt for tinting the epoxy and skip the painting step.

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