Experimental #21 Opaque is a UV reactive glass with a white base. These rods present a smooth minty green color with a bright green UV reaction caused by NS-137 Ill-uminati content in the glass. This color luminesces best with a 365nm-395nm LED flashlight. As with many opaque colors, this glass can suffer from boiling issues if pushed too fast or hot, so let the heat sink in for best working results. This glass does contain uranium.