A simple procedure for preparing a silica filler possessing both the necessary structure and surface character to be useful as a reinforcing filler for silicone elastomers has been developed. The novel, one-step process involves hydrolysis and condensation of alkyl silicates in the presence of a silica surface treatment agent exemplified as follows: (see PDF for diagram) Only easily recycled by-products are generated during the synthesis of the new WPH silica. Performance of the resultant WPH silica filler in reinforcing silicone elastomers will be discussed in detail in Part II of this series, while their use in silicone elastomers for optical applications will be described in Part III.