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Marbles were originally made by hand.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. Glass marbles can be fashioned through the production of glass rods which are stacked together to form the desired pattern, cutting the rod into marble-sized pieces using marble scissors, and rounding the still-malleable glass.
One mechanical technique is dropping globules of molten glass into a groove made by two interlocking parallel screws. As the screws rotate, the marble travels along them, gradually being shaped into a sphere as it cools. Color is added to the main batch glass and/or to additional glass streams that are combined with the main stream in a variety of ways.