Opaque antique white glass attained its greatest popularity at the end of the 19th century. American glass manufacturers made antique milk glass tablewares as a substitute for more costly European china and glass. By adding ash or oxides to clear glass, opacity was achieved to create this ware. The addition of various coloring agents turned milk glass into blue, pink, yellow, green and even slag glass colors. Antique milk glass has been made in numerous forms and shapes in this country and overseas and continues to be made at present. Some vintage products are reissues and reproductions of earlier forms, but collectors favor antique milk glass from the pre-World War I era especially, animal-covered dishes by makers such as Atterbury, Challinor-Taylor, Flaccus, Westmoreland, and McKee.