In art, several important "bronze" sculptures created in the 19th century are actually electrotyped copper, and not bronze at all; sculptures were executed using electrotyping at least into the 1930s. In printing, electrotyping had become a standard method for producing plates for letterpress printing by the late 1800s. It complemented the older technology of stereotyping, which involved metal casting. By 1901, stereotypers and electrotypers in several countries had formed labor unions around these crafts. The unions persisted into the 1970s, but by the late 20th century, after more than a century in widespread use for preparing plates, the two technologies had been bypassed by the transitions to offset printing and to new techniques for the preparation of printing plates.