As a ceramics teacher in a high school, I am always looking for new ways to help with studio processes and clean-up. One way that I have found to cut down on the usage of studio bowls is to create our own reusable slip bowls.
This is done by first creating a simple pinch pot out of a small amount of clay. The pinch pot is then flattened on the bottom to allow it to sit on the table without rolling over. It is then filled with water. As you work, the clay will begin to dissolve and slip can easily be made by rubbing the inside of the pot with a brush. The slip can be controlled and used in a variety of desired thicknesses from thin to thick. When you are finished working, reuse the clay container for less mess and no waste.