Subtitles section Play video Print subtitles comes in these huge sacks dry and absolutely pitch. Black powder reaches a smooth consistency. They mix it with water to create a slurry. The amount of black carbon in the mix determines the shade of the cement. Too much water and the tile won't hold together too little can ruin the pattern. Every design has its own metal stencil. Workers pour the slurry into the voids. One of the hardest parts is to get crisp lines and then they add the backing layer that also has carbon. The first layer is more for the aesthetics and the pattern that really comes out. The back layer is frustrating the factories. Only hydraulic press squeezes the tile into shape and helps it set the firmed up tiles still need to strengthen through a process called water curing. That means they get hosed down every day for nearly a month, cement tiles require a lot of extra polishing even after they're put in place.