For several centuries glassmakers made use of lead in glass in a wide range of concentrations to achieve glass that was highly suitable for handworking. During the 1990s the use of such toxic, heavy metals in glass as lead and barium became a controversial issue because of environmental considerations, and the possibility of lead leaching out of the glass container into its contents. The benefits derived from the use of lead are that it imparts a very long working-range to the glass, especially when it completely replaces lime, and that lead, being a heavy metal, increases the density of the glass, which in turn raises the refractive index of the glass, thereby making the glass far more brilliant.