The Romans and Egyptians used a mixture of sand and sea shells for silica, with lime and hardwood ash as the source of soda Small differences in oxide content can drastically affect the final color of a glass; yet colors and tints were reproduced many times with consistency.Copper was used to make green and ruby-red glass; iron produced black, brown, and green; antimony, yellow; and manganese was employed to make purple and amethyst glass. An opaque white glass, made by using tin, was important in glass cameo work.