cabosil for a filler ?
 

A friend told me that cabosil is made of glass and is very hard and brittle. So why would it make a good bonding agent?

Re: cabosil for a filler ?
 

"Glass" is a mixture of silicates (from sand) and a metallic oxide.

Cabosil is fumed Silica made by Cabot Industries. It is a very low density fluffy powder when mixed into epoxy, makes it thicker, less dense, and easier to sand when cured.

While both are silicas, they have completely different properties and structures. Cabosil isn't "Glass".