How to Use Concrete Sink Molds

Set a piece of cardboard over the cabinet opening where you plan to install the concrete countertop with the concrete sink to create a platform over the open cabinet top. Set the template of the sink onto the cardboard located where you wish to install the sink. Check the cabinets beneath to ensure that placement of the sink will not overlap any of the cabinet’s structural elements. If the sink is clear, measure the location of the template in reference to the rear and sides of the cabinet.

Place the template upside down in the body of the concrete countertop form. Use the measurements taken to position the template within the form. Trace the outline of the template onto the form with a pencil, and then remove the template from the form.

Place a bead of silicone caulk around the rim along the top of the rubber sink mold. Place the mold upside-down onto the form, with the edges aligned with the outlined template. The bottom of the form will create the top of the counter, and so you want to place the sink so that the opening of the sink is pressed to the bottom of the form. Press down on the mold to seal it into place against the countertop form.

Combine concrete mix with water in a large bucket to form a concrete that just holds together when formed in the hand. Add any colorants to the concrete during the mixing process. Put on a pair of rubber gloves and then press this concrete into the form by hand, building it up to a 1/2-inch layer over both the form and the sink mold. Make sure you do not cover the tops of any of the drain or faucet holes in the sink mold.

Cover the concrete with a layer of steel mesh, cut to fit the form’s shape with tin snips, less 1 inch on each side. Before placing the mesh into the form, dip it in acetone and scrub it on both sides with a steel brush to clean the material. You don’t need the mesh over the bowl section. Fill the form above the mesh with concrete to the rim, pressing it through the mesh as you go along. Let the concrete cure for about two weeks.

Take off the sides of the countertop form. Flip the form over onto a pair of boards spaced widely enough to accept the sink between them. Pull off the base of the form. The sink mold should come off along with it.