Glass Block also known as Glass Brick, is an architectural element made from glass. The appearance of glass blocks can vary in color, size, texture and form. Glass blocks provide visual obscuration while admitting light. The modern glass block was developed from pre-existing prism lighting principles in the early 1900's to provide natural light in manufacturing plants. Today glass blocks are used in walls, skylights, and sidewalk lights.
The texture and color of Glass Blocks can vary in order to provide a range of transparency. Patterns can be pressed into either the inner void or the outside surface of the glass when it is cooling in order to provide differing effects. Glazes or inserts may also be added in order to create a desired private or decorative effect.
Glass Blocks provides natural and unnatural light to be utilized while serving as a decorative addition to an architectural structure. Hollow glass wall blocks are manufactured as two separate halves and, whilst the glass is still molten, the two pieces are pressed together and annealed. The resulting glass blocks will have a partial vacuum at the hollow center which contains Argon Gas giving it a desirable thermal insulation value. Due to the hollow center however, wall Glass Blocks do not have the load-bearing capacity of masonry bricks and therefore are utilized in curtain walls in showers, offices, windows, out doors and other architectural locations.
Older manufactured Glass blocks have an R-Value between 1.75 and 1.96, close to that of thermopane windows. Modern manufactured Glass Blocks are injected with Argon gas and having a layer of low-emissivity glass between the halves, which increases the insulative (U) value to 1.5 W/m²·K, which is between triple glazed windows (1.8 W/m²·K) and specialty double glazed windows with advanced frame and coatings(1.2 W/m²·K).
Glass blocks used in flooring are normally manufactured as a single solid piece and are typically referred to as glass block pavers. These blocks are normally cast into a reinforced concrete grid work or set into a metal frame, allowing multiple units to be combined to span over openings in basements and roofs to create skylights. Again, Glass wall blocks should not be used in flooring applications due to the process in which they are manufactured does not allow them to be load bearing.
Some hollow glass wall blocks are available in colored variants. These colored variants fall into two categories.