Marble (toy) conventions. Additionally, many glass artisans produce art marbles for the collectors' market only, with some selling for thousands of dollars. Marbles are made using many techniques. They can be categorized into two general types: hand-made and machine-made. Marbles were originally made by hand. Stone or ivory marbles can be fashioned by grinding. Clay, pottery, ceramic, or porcelain marbles can be made by rolling the material into a ball, and then letting dry, or firing, and then can be left natural, painted, or glazed. Clay marbles, also known as "crock marbles" or "commies" ("common"), are made of slightly porous clay, traditionally
Liquid marbles at the solid-air interface, the interfacial liquid marbles are constructed on the hexane/water interface using water droplets with a surface coating composed of nanoscale materials with special wettability (Figure 2). To realize interfacial water marbles at hexane/water interface, the individual particle size of the surface coating layer should be as small as possible, so that the contact line between the particles and the water reservoir can be minimized; special wettability with mixed hydrophobicity and hydrophilicity is also preferred for the interfacial water marble formation. The interfacial water marble can be fabricated by firstly coating a water droplet with nanomaterials with