Translucent cast glass is explored as an alternative restoration material for marble monuments, addressing the gap between imitative replacement and contrasting modern insertions. Using the Parthenon as a reference case, the thesis asks whether glass can reveal absence without pretending to be marble, while remaining visually compatible with the original fabric. Its novelty lies in combining three separate questions: the optical design of translucent veined cast glass, expert perception of glass within a conservation narrative and reversible interface strategies through sacrificial mortar recipes. The methodology combined conservation theory, kiln-cast glass experiments, optical characterisation against Pentelic marble, daylight and night-time renderings, expert surveys, and mortar/interface tests. The results show that moderated translucency, warm colour behaviour, gloss and internal veining can create a marble-like yet distinguishable intervention. The thesis concludes with a feasibility-level design guideline, defining glass not as a replacement for marble, but as a material capable of making loss legible.