What are the key differences between fumed and precipitated silica, and why does the distinction matter for pricing?

What are the key differences between fumed and precipitated silica, and why does the distinction matter for pricing?
Fumed silica is produced by flame hydrolysis of silicon tetrachloride, yielding extremely fine primary particles with only external surface area, while precipitated silica is made by acidifying sodium silicate in water, creating porous particles with large internal surface area. This structural difference drives performance and cost. Fumed silica commands a significant price premium due to higher energy input and specialized equipment, and it is favored in silicone rubber, adhesives, and coatings where rheology control and purity are critical. Precipitated silica is cheaper and dominates rubber, footwear, and toothpaste applications. In China, over 90% of silica consumption goes to rubber, with about 60% of that into shoe soles, making precipitated silica's price highly sensitive to downstream footwear demand and sodium silicate feedstock costs.