You guys ever use this stuff as a thickener? It works awesome and is lightweight as air. Cheap too… i paid $7 for a one gallon container today. I had to do some bondo-ish filler work but polyester would have been too brittle so I mixed the fumed silica with a shore D-80 epoxy. I’ll sand down the fill work tomorrow but it should be very good as I’ve used this stuff before.
Good cheap filler and filleting compound.
It is good for making a custom viscosity filling/fairing compound. But one must keep in mind that resin pot life will be significantly shortened from the insulating properties of the filler.
is that the white dust like thingy, very light, and the resin turns foggy when you put it in? if so, i’m using it too 
yeah it’s like a jar of white dust bunnies 
I did notice that TET… the gel time of the resin was cut in half.
fine chopped fiberglass makes a good filler too, adds strength to the filler. I used to chop up carbon fiber cloth into very tiny pieces and mix that in also.
i had an air bubble in a mold, where the fiberglass just wouldnt sit down, and i filled it up with epoxy and that dust, i thought about milled fiberglass, but this you can use a syringe (without the needle) to pour it in tight spots
fumed silica can be quite brittle on its own. we tend to use a blended glue powder from west systems, it is a bit more forgiving and contains cotton flocking and i believe q cells aswell.