Concrete Casting: Moldmaking for a Concrete Sink





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Published on Feb 11, 2008

How to cast a reproduction concrete sink basin by making a 2-part Vytaflex urethane production rubber mold.

Step One: Construct Mold Box
Measure original sink basin. Use melamine board (formica coated) to make mold box segments, which will ensure easier separation from mold rubber.

Step Two: Create Spacer Board
Center model on board to use as a spacer board. Create perimeter outline for cutting. Center model on baseboard. Position spacer board and align with baseboard. Mark alignment point on baseboard and spacer board. Use modeling clay to create a gasket. Use non-sulfur based clay only. This will prevent rubber from going underneath model. Modeling clay will fill negative space between original model and spacer board. Remove excess clay.

Step Three: Acorn Nuts will be Used to Create Registration Keys
Hot melt glue will be used to secute acorn nuts. Place extra key for mold orientation.

Step Four: Assemble and Seal Mold Box
Screw melamine boards together with dray wall screws. Seal seams with hot melt glue.

Step Five: Release Mold Box and Model
Apply Universal Mold Release to all surfaces.

Step Six: Measure, Mix and Pour VytaFlex 40 Mold Rubber
VytaFlex 40 mix ratio: 1 part A to 1 part B by volume. Measure, mix, and pour the liquid rubber. Do not pour beyond sink hole. Let rubber cure for 16 hours at room temperature.

Step Seven: Prepare to Make Second Half of Mold
Use non-sulfur clay to fill in surface irregularities. Measure and cut reverse side baseboard. Secure reverse side baseboard. Turn over mold box. Remove original baseboard to expose concave half of model. Remove spacer board. Remove acorn nuts from rubber mold. Remove clay gasket. Remove clay residue.

Step Eight: Seal Drill Holes and Release Mold Box
Fill drill holes with non-sulfur clay. Seal seams with hot melt glue. Apply Universal Mold Release to all surfaces.

Step Nine: Measure, Mix and Pour VytaFlex 40 Mold Rubber
Let rubber cure for 16 hours at room temperature.

Step Ten: Demold Original Model
Remove mold box side walls. Gently pry original model to expose mold cavity. Concrete mold ready for casting.

Step Eleven: Casting Concrete
Apply In and Out II release agent to all surfaces. Secure 2-part mold with straps and baseboards. Place mold on vibration table. Fill mold with concrete and vibrate. Let concrete cure 24 hours.

Step Twelve: Demold Concrete Casting
A perfect concrete reproduction of the original. Concrete mold is ready to be cast again.

Make It Now! with Smooth-On

Adult Supervision Required
Keep Out Of Reach Of Children


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