Designer interest in glass block has revived and continues to grow. Manufacturers have responded by adding new colors, surface patterns, and shapes to their product lines. Just as new patterns and colors have given designers a way to alter the look of glass block walls and panels, new block shapes have made possible new ways of using the material. Block designs that incorporate 90-, 45-, and 22 1/2-degree angles allow contractors to build cleaner corners, smoother curves, and tighter radiuses than ever before. SPECIALTY BLOCK TYPES There are three categories of specialty block: angled (90 and 45 degrees), radius (22 1/2 degrees), and smooth end. Corner block, roughly square in plan, are used to form sharp corners in partitions, walls, and panels. Another specialty unit is standard in all ways except for its 45-degree bullnose edge. DESIGN CONSIDERATIONS There are three key design considerations for specialty glass block walls: proper perimeter support, adequate joint reinforcement, and compatible mortar. Glass block is not a loadbearing material; rather, it is always used as infill within a structural frame. It cannot bear compressive loads and offers limited resistance to lateral loads. Reinforcement wire is used in all glass block panels or walls, but some additional reinforcement is required for specialty block. Because glass block is not porous and does not absorb water, mortar should be stiffer than that used with brick and block. The general recommendation for glass block is to use mortar that meets ASTM C 270 requirements for Type S.