Thanks for the answer, Joe--even though it wasn't what I'd hoped to hear. :(
It's the largest of the three pots with the concrete. The other two have been used the same way but seem to have a soft substance that will chip out fairly easily, so it's not a total loss.
I am a bonsai artist. Recently, I discovered a real treasure at an estate sale--a set of three bonsai pots. One of them had been filled with concrete and large pebbles to make it a heavy base for artificial trees. I want to remove the concrete. The pot is of fired clay with fired glaze. The...