Glass blocks have been used for many years to create transparent walls and decorative features. More recently, acrylic substitutes have come onto the market that offer a similar look but have different physical characteristics.
Glass and acrylic blocks are transparent, allowing plenty of illumination to pass through. They're often square in shape and can be textured for decoration or privacy. Windows and walls, such as shower walls, can be made from these blocks.
Glass is a traditional material with a proven track record. Its properties and limitations are well-understood. Glass blocks are durable and attractive. Glass blocks, which have a greater compressive strength, can also withstand far higher temperatures than acrylic blocks.
Acrylic blocks are cheaper and lighter than glass. They can be moulded in different shapes, such as triangles and octagons, that weren't available with glass blocks. Glass block windows are too heavy to be made to open in most cases, where acrylic block windows are not. Acrylic block units can be bought all in one piece and installed like ordinary windows, unlike glass blocks which must be laid individually.