We compared how much energy is transmitted through a
soda lime glass
vs.
sapphire. In a nutshell, soda lime glass is better than sapphire, transmitting more of visible light in the 475 – 590 nanometers spectrum. This spectrum covers the range of colors from blue to orange. Starting from longer wavelength such as red, sapphire transmits more light than soda lime glass. In the infrared, sapphire clearly shows its optical advantage over soda lime glass. The same advantage of sapphire is evident in shorter wavelength, such as violet color.
Soda Lime Glass vs. Sapphire Transmission Curves
For the purposes of our test we used a NPT sight glass, Part Number 410s11, and a 5 mm thick C-axis sapphire bonded to a 316 stainless steel housing.
Sight Glass, Soda Lime Glass fused to NPT-1 inch
Zero distortion of the sight glass in the right side of the image.
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