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Make a template of the counter using 1/4" sheets of luan.
Once you get the right shape, you can trim the luan with a utility knife and a straight edge. Once they're cut, carefully glue the pieces together with hot glue, and write notes on the template to indicate the walls and finished edges.
Cut the forms out of a piece of 3/4" Melamine and screw them together. Lay steel mesh into the form to add strength to the concrete.
Note: Melamine is made from plastic resin, which gets heated to form a tough, impervious surface similar to laminate. This smooth surface will release the concrete easily.
Pour a bag of the concrete mix into a wheelbarrow. To mix the color, pour a half gallon of water into a bucket along with a pint of the color, then add one gallon of water and stir.
Add the color mix (Image 1 -- ash was used for this particular project) to the dry powder a little at a time. When the mix is ready, add it into the form.
Smooth it out with your hands and be sure to work out any large air bubbles.
Clip the wires off the form and then begin "screeding" (a smoothing process) the mixture, by sawing a board back and forth over the top (Image 2). Take a palm sander and vibrate the sides of the mold to get rid of air bubbles.
Take a magnesium float and go across the top of the mold to seal it and get rid of any bumps. Let the mold sit for 45 minutes to an hour for it to harden.
Note: It takes a full 28 days for concrete countertops to cure.
To begin installation, if you've created the concrete countertop yourself and it has cured for 28 days, remove the Melamine mold and apply a penetrating sealer using a foam brush (Image 1). Top this off with a coat of beeswax using a soft cloth.
Note: Sealant dries to the touch in about one hour, but it should be left for 24 hours to dry completely.
Apply a bead of silicone to the top of each cabinet and slide the concrete into place (Image 2).
For the seams, apply a gray sealant (Image 3) made from black and white silicone.
Note: To maintain the countertops, simply apply beeswax every one to three months (according to how much you use your counters) and buff with a soft cloth.