I do not know much about opaque glass but according to Wiki:
"TiO2 is also an effective opacifier in powder form, where it is employed as a pigment to provide whiteness and opacity to products such as paints, coatings, plastics, papers, inks, foods, medicines (i.e. pills and tablets) as well as most toothpastes. Opacity is improved by optimal sizing of the titanium dioxide particles."
"Titanium dioxide, particularly in the anatase form, is a photocatalyst under ultraviolet light. Recently it has been found that titanium dioxide, when spiked with nitrogen ions, or doped with metal oxide like tungsten trioxide, is also a photocatalyst under visible and UV light."
The opacity of the vase and how the whole thing looks under UV could be linked to the possible use of Titanium Oxide fibres .... may be worth a UV photo... just a thought ......