During the 19th century, dolls' heads were often made of porcelain and combined with a body of leather, cloth, wood, or composite materials, such as papier-mâché or composition, a mix of pulp, sawdust, glue and similar materials. With the advent of polymer and plastic materials in the 20th century, doll making largely shifted to these materials. The low cost, ease of manufacture, and durability of plastic materials meant new types of dolls could be mass-produced at a lower price. The earliest materials were rubber and celluloid. From the mid-20th century, soft vinyl became the dominant material, in particular for children's dolls. Beginning in the 20th century, both porcelain and plastic dolls are made directly for the adult collectors market. Synthetic resins such as polyurethane resemble porcelain in texture and are used for collectible dolls.