Filigree is a elegant piece of jewellery metalwork made with twisted threads (gold and silver usually) or combining of the same curving motifs. It looks like the lace made of metal, and in recent centuries remains popular in Indian and other Asian metalwork, and French from 17th to the late 19th century. It should not be confused with ajoure jewellery work; filigree is made of threads being soldered together to form an object and ajoure involves holes being punched, drilled, or cut through an existing piece of metal.
Enamel was first applied commercially to sheet iron and steel in Austria and Germany in about 1850. Industrialization increased as the purity of raw materials increased and costs decreased. The wet application process started with the discovery of the use of clay to suspend frit in water. Developments that followed during the twentieth century include enameling-grade steel, cleaned-only surface preparation, automation, and ongoing improvements in efficiency, performance, and quality.