How to Make Concrete Bath Sinks

Make the Form

• 1

  Measure the diameter of the bowl or shape you are using as a mold. Cut two square pieces of non-stick Melamine board slightly larger than the diameter of the form, using a circular saw.

• 2

  Set the mold face down on one of the Melamine boards. Trace the shape of the mold onto the Melamine board. Drill a hole large enough to fit a jigsaw blade inside the line. Place the jigsaw blade in the hole and start the jigsaw. Cut out the shape of the mold.

• 3

  Place the mold face down on the uncut Melamine board. Seal around the edges of the mold with modeling clay.

• 4

  Set the cut out Melamine piece over the form and align the two boards. Mark on each side where the two boards line up. Seal the edges around the mold with modeling clay. Place a bead of modeling clay around the drain opening in the bottom of the model at this time as well.

• 5

  Glue two acorn nuts diagonally 1 inch from each of the four corners of the Melamine piece with the hole cut in it, using a hot melt glue gun. Placement doesn’t have to be exact. Glue a third acorn nut to one of the corners. When removed, the impressions from these nuts serve as posts to help align the pieces of the mold.

• 6

  Measure how deep you need to make the mold. Measure from the Melamine board on the bottom of the stack past the mold and allow at least another 2 inches. Cut four pieces of Melamine board to that thickness to create walls for the form box. Attach the walls to the base and to each other with drywall screws.

• 7

  Run a bead of hot melt glue along all seams. Spray mold release product over the entire mold and form box.

• 8

  Mix one part mold rubber with one part catalyst for at least three minutes, using a stirring stick or a paddle attachment for a drill. Scrape the bottoms and sides of the mixing container frequently.

• 9

  Pour the mold rubber into the form box. Only add enough rubber to come to within an inch of the bottom of the model. Allow the rubber to cure for 16 hours at 72 degrees Fahrenheit.

• 10

  Measure the inside dimensions of the top of the form box. Cut a piece of Melamine board to those dimensions. Hold the board in place on the form box with drywall screws.

• 11

  Flip the mold box over. Unscrew the screws holding the bottom of the box in place. Set it aside as well as the board with the center cut out of it. Take all of the clay off the mold. Wipe the mold to remove any traces of clay. Remove the acorn nuts.

• 12

  Insert modeling clay into the screw holes in the form box. Seal all seams with a bead of hot melt glue. Spray mold release product over the cavity.

• 13

  Mix another batch of equal parts mold rubber and catalyst. Pour the rubber mixture into the form box. Fill the box completely. Allow the rubber to cure for 16 hours at room temperature, or 72 degrees Fahrenheit.

• 14

  Unscrew all screws holding the form box together. Pry off the sides and the bottom piece. Gently remove the top section of the mold from the bottom piece. Take out the model.

Pouring the Concrete Sink

• 15

  Cut a Melamine board the same dimension as the original base board. Cut a 4-inch hole in the center of the board using a hole saw.

• 16

  Wipe mold release product on all surfaces of the mold. Put the mold together, aligning the indentations made by the acorn nuts. Set the full size Melamine board under the larger portion of the form and the board with the hole in it on top. Secure the mold and boards together with packing straps. Set the mold on a vibrating machine.

• 17

  Mix ready-mix concrete according to package directions. Pour concrete into the opening in the mold while the vibrating machine is operating. This helps settle the concrete into all the nooks of the mold as well as disperse any bubbles in the concrete. Allow the concrete curing time, following package recommendations.

• 18

  Remove the straps holding the mold pieces together. Pry the concrete out of the mold carefully. The sink is now ready to install.