Milk glass

Milk glass is an opaque or translucent, milk white or colored glass, blown or pressed into a wide variety of shapes. First made in Venice in the 16th century, colors include blue, pink, yellow, brown, black, and the white that led to its popular name.

Milk glass contains dispersion of particles with refractive index significantly different from the glass matrix, which scatter light by the Tyndall scattering mechanism. The size distribution and density of the particles control the overall effect, which may range from mild opalization to opaque white. Some glasses are somewhat more blue from the side, and somewhat red-orange in pass-through light.

The particles are produced via addition of opacifiers to the melt. Some opacifiers can be insoluble and only dispersed in the melt. Others are added as precursors and react in the melt, or dissolve in the molten glass and then precipitate as crystals on cooling; this is similar to color production in striking glasses, but the particles are much bigger.

The opacifiers can be e.g. bone ash, or tin dioxide and arsenic and antimony compounds. They are also added to ceramic glazes, which can be chemically considered to be a specific kind of milk glass.

First made in Venice in the 16th century, colors include blue, pink, yellow, brown, black, and white. Some 19th-century glass makers called milky white opaque glass "opal glass". The name milk glass is relatively recent.

Made into decorative dinnerware, lamps, vases, and costume jewelry, milk glass was highly popular during the fin de siècle. Pieces made for the wealthy of the Gilded Age are known for their delicacy and beauty in color and design, while Depression glass pieces of the 1930s and 1940s are less so.

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