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%