: Usually one adds the hardener to the resin, mixes it well, and then
: adds filler material to suit one's purpose. Perhaps adding the
: filler before the hardener caused an imperfect mix.

: Et

Et: that seems unlikely with microballoons, although more absorbent filler might perhaps soak up much of the resin and upset the mix ratio of the remainder. In that case adding more hardener would have upset the ratio even more.

At my age Senior Moments, as they are called, occur more frequently with every passing year. When I have to mix something I put all the ingredients in oder of use on the workbench, and move them elsewhere as I use them. Even then . . .

Which is why I prefer to use one-part glues and paints!