His materials are little more than smoke and water vapor, and the results vary with the size and temperature of the location. The space must be cold and damp, with no air circulation. Smilde creates a wall of water vapor with the type of spritzer you might use on houseplants. A smoke machine then sends a puff of faux fog on a collision course. He likes to keep the clouds no bigger than six feet so they don’t fall apart too quickly. “I really like my clouds concentrated, with a lot of texture,” he says.