Cold porcelain and other air-dry clays can be flattened into thin sheets using a pasta machine, but sometimes you need a larger sheet or even something thicker than you can get with the pasta machine. The following video from Marisol Romero shows how to roll and flatten cold porcelain paste using a roller and thickness guides. While
rolling is a common practice in modeling with cold porcelain, there are some issues to take into account at the time of stretching the paste such as spreading it evenly & keeping the same thickness throughout the extended area.
Video narration is in Spanish, but even if you don't understand the language you should be able to follow along. Marisol clearly and carefully shows each step, demonstrating with different thickness sticks and a smooth roller.
We've previously featured a few other videos from Marisol showing the proper way to wrap Styrofoam shapes with cold porcelain (without getting cracks or trapped air)...see Labels "Styrofoam" to view those videos. Her videos are very educational for those just getting started with cold porcelain. She also offers classes on her website (about $20 each course).