Specific Gravity


Definition of Specific Gravity


Specific gravity is a measure of the density of a mineral or in this case optical lens material.  It is derived from the density of the lens material divided by the density of water.  Since water's density equals 1 gram per cubic centimeter (at specific conditions), then a mineral's specific gravity (SG) would also correspond to a mineral's density as expressed in grams per cubic centimeter (g/cm3).  Since a glass lens has a specific gravity of 2.54, then it is nearly three times as dense as water as well as Trivex.



Table Of Various Materials by Wieght

Index of Refraction

Specific Gravity

Trivex (1.53)
1.11
Hoya (1.56)
1.20
Polycarbonate (1.59)
1.21
Sola (1.53)
1.21
Plastic (1.50)
1.32
Essilor (1.60)
1.34
Nikon (1.60)
1.34
Signet (1.60)
1.34
Sola (1.60)
1.34
Varilux (1.60)
1.34
Pentax (1.66)
1.35
Essilor (1.67)
1.35
Hoya (1.67)
1.35
Nikon (1.67)
1.35
Kodak (1.67)
1.35
Varilux (1.67)
1.35
Essilor (1.56)
1.36
Nikon (1.56)
1.36
Varilux (1.56)
1.36
Seiko (1.67)
1.36
Optima (1.66)
1.36
Hoya (1.70)
1.41
Essilor (1.74)
1.46
Crown Glass (1.52)
2.54
Glass (1.60)
2.60
Glass (1.70)
3.20
Glass (1.80)
3.66








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