opalite
Opal glass, formed into tiles or bricks.
opalite: white or cream glass brick that diffuses light evenly
Opalite is a opaque or milky glass unit, typically 190mm to 240mm square and 80mm to 100mm thick, cast into tiles or interlocking bricks for use in interior partitions, windows, and decorative panels. The material consists of soda-lime glass with added bone ash or similar opacifiers that scatter light internally, creating a frosted or opalescent appearance rather than true transparency. It does not transmit a clear image through its thickness, but rather spreads illumination diffusely across its surface and beyond.
The primary trade advantage of opalite is light transmission without visual privacy loss. A partition of opalite bricks allows daylight or artificial light to pass through interior walls, reducing reliance on supplementary lighting in connecting spaces, while preventing occupants on either side from seeing distinct shapes or movement. This made it popular in mid-twentieth-century commercial and institutional buildings for washrooms, stairwells, and office divisions.
Material and construction variants
Opalite units are usually supplied as dry-stack interlocking bricks or as tiles bedded in mortar. The glass itself runs 6mm to 12mm in wall thickness. Some formulations include a faint tint, pale green or blue, though cream or white is standard. Load-bearing opalite walls require a steel or concrete frame, as the glass provides no structural capacity; the units are non-load-bearing infill only. Grout joints are typically 10mm wide and finished flush or recessed.
Common problems include cracking under thermal stress, settling of the supporting frame causing shear failure at joints, and discoloration or clouding from water ingress into edge seals. The material is brittle and difficult to cut or drill on site; any opening must be planned at the manufacturing stage. Cleaning is straightforward but must avoid abrasive pads, which scratch the surface.
The name derives from opal, the gemstone, because the milky, light-scattering quality of the glass resembles opalescence. In some markets it is called opal glass block or structural glass tile. It remains in use for bathroom partitions, stairwells, and accent panels in contemporary buildings, though tempered glass and polycarbonate have captured much of the market for new construction.