Milk glass is a relatively recent name for opaque, milky white or colore glass, that is blown or pressed into a wide variety of shapes. Animal-shaped covered dishes are popular collectibles. First made in Venice in the 16th century, the white color is achieved through the addition of tin oxide. 19th-century glassmakers called milky white opaque glass "Opal". Other milk glass colors include blue, pink, yellow, brown, and black.