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.

Principle

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.