Most applications of glass block need the strength and permanence of mortar, which creates a strong gridded joint pattern. But a new silicone installation system that creates glass block panels with less prominent joints is gaining favor for some jobs. The system uses rigid plastic framing channels, flexible plastic spacer strips, and clear silicone sealant to achieve an almost seamless look. SILICONE BENEFITS Besides yielding a difference in appearance, silicone installation reduces mess and simplifies cleanup. LIMITATIONS Silicone-jointed panels currently are limited to smaller sizes than mortared panels. Silicone joints are only 1/8 inch, leaving little room for adjustment. TOOLS AND MATERIALS All materials for silicone installation-plastic channels, spacer strips, and a proprietary silicone sealant-are available from the system manufacturer. Required tools include a fine-toothed hacksaw, electric drill and 1/8-inch drill bits, screwdriver, screws, razor knife or heavy shears, string, putty knife, shims, finishing tool, glass cleaner, single-edge razor blades, cloth rags, and a 2-foot level. A high-quality, quick-release caulking gun also is essential.