I've been using glass & epoxy to effect some repairs. One surface was very irregular so the plan was to trowel on thickened epoxy, smooth on the glass squeezing out any thickened epoxy then add unthickened epoxy if necessary to wet out the glass.
I normally use Cab-o-Sil to thicken but this time I used micro balloons. After I finished there was maybe 1/4 - 1/2" of both thickened and unthickened in little pot pie type pans. The thick went off like gang busters...once it started, it got rock hard in minutes. It also expanded by about 3X. Meanwhile, the unthickened had barely gotten syrupy.
What's going on with that? The fast hardening and - especially - the expansion.
dadiOH