I would like to address some of your points in order to clarify the definitions of colloidal silica, fumed silica, and hydro phobic silica.
First, for colloidal silica, you're correct that it does not have a chemical bond with refractory fibers. However, this does not mean that it doesn't form a mechanical bond with them. When sodium silicate is fused with refractory fibers, it forms a non-chemical bond that is mechanically more stable than the chemical bonds formed by other materials such as fumed or hydro phobic. This explains why sodium silicate has been shown to perform better than other types of silica in kilns.
Second, you state that hydro phobic silica is used primarily to thicken resins. However, this is not true—hydro phobic silica is used primarily to purify resin during the manufacturing process. It does not have any other uses in manufacturing equipment or equipment components. Hydro phobic can be used for its other beneficial qualities, but these are secondary benefits rather than primary reasons for using hydro phobic