Antique glass knobs crafted between the mid -19th and early 20th centuries hold a fascinating secret. These seemingly ordinary pieces of hardware often concealed a surprising transformation. To achieve the coveted crystal clarity, glassmakers of the era incorporated manganese dioxide into the molten glass. However, this additive possessed an unexpected characteristic: over time, when exposed to sunlight, the glass would develop a captivating purple hue, a phenomenon known as solarization.
It’s a quirk of history that has delighted and puzzled collectors for generations. We often encounter customers who present a curious pair: one knob clear as crystal, the other bathed in a mysterious purple glow. This subtle color disparity offers a intriguing clue to the knob’s history: the clear knob likely adorned an interior hallway shielded from sunlight, while its counterpart basked in the radiant embrace of a sunny room.
Interestingly, modern glass knobs are immune to this enchanting transformation. While advancements in glassmaking technology undoubtedly play a role, the real turning point came during World War I when manganese was diverted for munitions production. As a result, the practice of using manganese dioxide as a decolorizer was curtailed, marking the end of this captivating chapter in glassmaking history.
How's that for a fun fact?
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