The goal of this portion of the borate glass lab is to experience the glass transition through observing the temperature dependence of viscosity. Students work in teams of two, drawing sodium borate glass fibers from prepared melts.
Crucibles containing the prepared borate glass, ready for reheating. The glass is heated to 900°C in a box furnace. TA Dilan Seneviratne demonstrates the procedure. A student removes a heated crucible with tongs. A student removes a heated crucible with tongs. The crucible, and its melted glass contents, glow orange for several seconds after removal from the oven. A student pours the molten glass to prepare for a draw (note the glass continues to glow). A student draws a long glass fiber, using a silica rod dipped in the molten glass. Drawing a second glass fiber directly from the crucible.