With the recent rapid development and interest in 3D-printing, the technology is greatly improving, however, challenges such as expanding the material palette available and producing prints with controllable and reproducible properties still remain. For glass 3D-printing, optical properties are key to a print's usefulness and success. Herein we provide a brief overview to direct and indirect methods for glass 3D-printing, describe how printing paste composition influences the opacity of the resulting print and report our efforts to use X-ray micro CT and thermogravimetric analysis to better understand how changes in paste composition lead to the changes in microstructure that are believed to control the bulk glass properties.