How To
Make a Concrete Bookend, With Chen Chen

“It’s not like it’s a science,” says Brooklyn designer Chen Chen as he’s mixing up a batch of cement in the Brooklyn studio he shares with collaborator Kai Tsien Williams, attempting to explain why he can’t offer an exact set of measurements for replicating his concrete bookends. They’re fitting words to have chosen, though, coming from him: The Shanghai-born, Wyoming-raised designer had two chemists for parents, and yet it seems like his entire practice has revolved around losing control during the design process rather than maintaining it. Since he joined forces earlier this year with Williams — a fellow Pratt grad who also runs the design fabrication business Three Phase Studio — the pair have spent most of their time together choosing offbeat materials like expanding foam and studio scraps and experimenting for weeks to see what kinds of unexpected effects they can elicit from them. Their breakout project this past May, designed for Sight Unseen’s Noho Design District pop-up shop, was a set of drink coasters made by wrapping bits of neon resin–soaked rope, animal bones, and offcuts around a wooden core, then slicing the whole mess open to see what might lay inside, with the results being different every single time. Granted the pair now profess to be working on an extremely functional storage system that, while modular and customizable, otherwise has the exact opposite ethos, but so far, it’s their work’s freewheeling and slightly bizarre quality that has so captivated the New York design scene. While the Metamorphic Rock Bookends you see here are technically a design of Chen’s, from just before he teamed up with Williams, we still thought they were a great example of the typical Chen-Williams methodology, so we asked for a lesson in how to make them, and Chen kindly obliged.

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Chen's Metamorphic Rock bookends, currently for sale through Phillips de Pury, are made from fine-grain concrete and stone-yard reject scraps. Their complete and utter randomness is part of their appeal — each one is entirely one of a kind, and even Chen himself doesn't really follow a set recipe when he's fabricating them.

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The ingredients are always the same, however: stones, Rockite cement mix (don't use anything else), cement sealer, and a three-sided mold. Chen constructs his molds from wood lined with aluminum flashing — which gives the bookends a smooth surface texture — then seals the seams with Plasticine to keep them watertight. "You could probably use a plastic bin that had relatively sharp corners," he says. "That would probably work too, and you might not even need the flashing."

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Chen's made bookends peppered with bricks and bits of chain, but the main ingredient is always stone — hence there are boxes filled with chunks of the stuff all over he and Williams's studio. They find them at a nearby stone yard, where they're basically considered garbage. "It's all stuff no one could use," Chen says. "If you even just walk around a stone yard, you'll normally find little chunks like these on the street."

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Depending on the size and shape of the stones he selects, “I’ll sometimes drill a few holes into the surface so there’s something extra for the cement to grab onto,” Chen notes. “It really helps. You just want to be careful if it’s a thinner piece, because a drill might shatter it.”

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Today Chen decided to keep his design simple, and opted for three pieces of stone in contrasting shapes and colors — one for each visible surface of the bookend. For the back two walls of the box, it's best to select stones with a flat side, which you should place completely flush against the aluminum so there's no gap for the concrete to seep into. The bottom surface of the box will be the bottom of the bookend, and doesn't need to be as considered, while the top will have the marble hunk in the foreground emerging from it.

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When it comes to mixing up the Rockite, "there's no real measurement to it," Chen says. He used 1.5 spray-paint caps–full of cement and added water very slowly and carefully until the mixture had the consistency of cake batter, or yogurt. "You want to keep it thick just to keep it from getting between the stone and the mold," he says. One important note: While working with the cement, keep a bucket of water nearby for washing any mixing cups or stirring sticks. After you finish, you can dump the sediment from the bucket into the garbage. "It's not harmful, you just don't want it clogging up your sink," Chen says.

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This is what the mold looks like once the mixture has been poured in, and the shape of the bookend is now visible. Any cement that splashes up onto the stones can be wiped off later, once the piece has set; it's so thin and easily re-hydrated that even after it dries, a wet cloth will suffice to remove it.

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Chen likes to keep extra pieces of wood or stone handy while he's making the bookends to shim up the mold, in case he wants to alter the angle of the cement (and thus the shape of the final object) immediately after it's poured in. In this case, he lifted the back legs up a bit to make the bookend a little wider at the base. It takes 15-20 minutes for everything to dry, and at that point the bookend should slide right out of the mold.

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Voila — our finished bookend. "Afterwards I file down the edges a bit with sandpaper to give them a little bit of a radius, so they don't chip," Chen says. He also coats the concrete surfaces with a cement sealer to protect them from water damage. If you try this at home, be sure to post photos of the finished results on our Facebook page!