Straight, curved, and serpentine walls and partitions are being built entirely of glass block. Architects are using patterned, textured, and tinted units and units that reflect or diffuse light. NONLOAD-BEARING ONLY Glass block usually is used in stack bond single-wythe construction--but only in nonload-bearing applications. LIGHT TRANSMISSION Most glass blocks are made of clear, colorless glass that admits the full tone of natural light. Hollow blocks with patterns pressed into their interior faces partly or totally distort images, creating visual privacy. Other units diffuse or reflect light. LESS HEAT GAIN Glass blocks can increase or reduce solar heat gain. Due to the large air cavity, hollow glass blocks also have greater thermal resistance than flat glass. SOUND, FIRE, AND CONDENSATION The high mass of glass block reduces sound transmission. In the same way that they reduce heat gain, the air cavities in hollow glass blocks increase fire resistance. Because of the glass block's insulating properties, moisture does not normally condense on it. DURABILITY Glass block is by far the strongest and most durable glazing material made. Compressive strengths for hollow units range from 400 to 800 psi. LOW MAINTENANCE Glass block panels require virtually no maintenance. The block doesn't deteriorate, doesn't need painting, and doesn't rot.