We used some makeshift plastic pistons so as not to potentially harm our expensive ceramic ones.
We manually dialed in our horizontal piston until we got a decent normal load (the panels that say 0.167 and 0.160 are in MPa and are the right and left load cells, respectively).
Then we slowly drove the plastic down through the rock. Plastic is pretty slippery, so we didn't get to very high shear stresses, which made me very happy for a first run. It all worked in a nice controlled manner, with data sent to a computer for later analysis. No major glitches, so next step: ICE!!