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- How to use a Mold to create a custom sink
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How to Use a Mold to Create a Custom Sink
Once you have your mold, how do you turn that into an integral sink in your countertop? First fasten it into position in your countertop mold. Buddy Rhodes' molds have plywood inset into the top of the sink mold. The mold is then placed onto the melamine and attached with screws from below. "You have to remember to back out those screws before you flip the counter over," said Rhodes. "The sink mold comes off with the countertop then we pull the sink mold out. Otherwise you would be putting forces on the sink that you probably don't want."
There are three basic ways to cast the concrete for the sink:
- Use very stiff concrete and simply hand apply it to the mold—this is the Buddy Rhodes hand-pressed method. You then come back and fill the honeycombing with the same or a contrasting color.
- Use concrete that is somewhat flowable but that can still be built up over the sink mold.
- Use a double mold (both inside and outside faces of the sink) and pour concrete inside and vibrate to get a smooth finish.
With the Buddy Rhodes method, the concrete is applied in two layers, each ¾ to 1 inch thick. Between layers, he places the reinforcement and the overflow. Rhodes has devised a clever but simple technique for incorporating an overflow into a concrete sink. "Take a piece of half-inch foam and cut a strip 1 inch wide to go from the top of the sink where the overflow hole would be to the drain," he says. "We pack the concrete around the mold then place the foam so it will be in the middle of the sink wall. Then the next day we take a 3/8 inch drill bit and drill through the concrete and into the foam to create the overflow hole. Then we take a funnel and pour lacquer thinner into the hole and it melts the foam out. Once the lacquer thinner flows out the bottom you know that the void is empty."
To use the double mold method, Karmody uses a sink mold and what he calls a top hat—essentially a bottom mold for the sink. "It's a collar that goes over the sink area and spreads out a few feet in each direction to makes sure the hydraulic head pressure does not push the concrete through. We place the concrete and vibrate normally and by the time any concrete reaches the end of that top hat it takes so much pressure that very little escapes."