Newbold Stone: Making a custom 1-off sink

This one is more of a technical "how-to" post, as well as an explanation of why one must charge a lot for custom cast sinks. Standard cast sinks are less expensive to do, because although you have to buy the mold, it can be used over and over, and that cost eventually amortized over the life of the mold.

This technique may not be the best method for this, but it is reasonably simple and requires low investment. It does, however, require an artists touch.

Step 1: Determine the client needs. Seems like a it would go without saying, but too many out there go without doing this important step. If you make that rudimentary mistake, then you have wasted a lot of time and earned an unhappy client. This client wanted a round sink, but not one that was perfectly round....she wanted it hand hewn looking.....the actual term was "hewny".

Step 2: Styrofoam Core. I use simple EPS sheets, which I laminate together with spray adhesive when necessary. Its the same stuff they make

coolers out of and I get it at Ace Contractor supply. It cuts easily with a hand saw and I shape it with a disk sander and some 150 grit paper. Once I get it close to size I smooth it with 220 grit by hand. Its best to have a good shop vac around at this point because you are going to look like you came out of a snowstorm.

Step 3: Plaster. The mold would kind of work at this point, but regardless of how much you sand it, the styrofoam would always leave a rough finish inside your sink. Hence, the foam gets coated with a sandable layer. I use curing joint compound, which comes as a powder, and prefer the 20 minute mud. I would imagine that straightforward plaster of paris would work for this, or premixed joint compound, but I am a big fan of the curing kind for speed and sandability.

Step 4: Repeat. Sand and replaster a few times, till you get it almost perfect, and then I fill in any final holes or bubbles with a layer of premixed joint compound (spackle) and let that dry. Final sand with 400 grit.

Step 5: Primer with Kilz. This seals the plaster coat. It dries fast, so it typically gets 3-4 coats.

Step 6: Gloss Oil Based Paint. Again, 3-4 Coats. I like to alternate colors....it makes it easy to see how much you are getting down.

Step 7: Make a drain. Foam with some tape around it is quick and dirty, or the appropriate PVC. Reusable rubber ones are available as well.

Step 8: Place and Cast. Definitely use mold release of some sort, otherwise the next step is going to be a real drag.

Step 9: Ta-Da, a sink. Acetone is your friend, as it will dissolve the foam and soften the plaster. some digging and scraping is going to be required, but then you are ready to sand the concrete.