Fabri-Cast 50: Always really brittle?

I got some Fabri-Cast 50 from Specialty Resins, and it is super brittle. I mix it in the described 1:1 ration, stir well, and let it cure. It turns white, I wait the allotted time, and de-mold. It is brittle and fragile. Thin bits have no flexibility at all, they just snap. There's no bending to it at all.

Is this normal for this type of resin? It's much weaker than Alumilite.