Glass Fiber Composition

(By Weight)

  E-Glass S-Glass
Silicone Dioxide 52 – 56% 64 – 66%
Calcium Oxide 16 – 25% 0 – .3%
Aluminum Oxide 12 – 16% 24- 26%
Boron Oxide 5 -10%  
Sodium Oxide & Potassium Oxide 0 – 2% 0 – .3%
Magnesium Oxide 0 – 5% 9 – 11%
Iron Oxide  .05 – .4% 0 – .3%
Titanium Oxide 0 – .8%  
Fluorides 0 -1.0%