Traditional assembly line manufacturing is speculative, costly and environmentally unsustainable. It is speculative because it commits substantial resources—energy, materials, shipping, handling, stocking and displaying—without a guaranteed sale. It is costly because each of these resources—material, process, people and place—involves expense not encountered when a product is manufactured at the time of sale. It is environmentally unsustainable because, no matter how much recycling is done, not using the resources unless actually needed is always a better path.As part of the RAGNAROK (Research on Advancing Glass & Nonorganic Applications to Recreate Objects & Kinetics) project in HP Labs, we identified glass as a promising candidate for additive manufacturing based on 3-D printing methods. Glass is a silica-based material. With 90% of the earth's crust composed of silicate minerals, there will be no shortage of silica resources. Glass is easy to recycle and is environmentally friendly. Glass is inexpensive but looks precious, is pleasant to the touch and is so familiar that customers will not be disappointed by its fragility—under certain conditions.A major need, and concomitantly a major challenge, for 3D printed glass is transparency. We will discuss several methods how to achieve it.