Thread: Removing old mortar from 2" floor tiles?

I recently ripped up sections of our bathroom floor to replace some boards and today I was going to relay the tiles.

I've managed to salvage about 85% of the ones I removed, (Oh, my aching fingers! ) the others I can't remove enough of the old mortar for re-use - they're the small 2"(ish) sq. ones which are right beggars to lay level when they're not in a "sheet" even when new. This wouldn't be a problem, 'cept apparently they're discontinued and the closest match are exorbitantly priced. The salesman used terms like "retro" and "funky" which set the ol' mental alarm ringing; who'd have thought that baby pooh brown was chic again?

Frankly, I'm not too concerned about colour matching (the house'll be demolished within a couple of years) but cost is a major concern...

...so any ideas for safely cleaning up the old ones? I've already removed the grout and cleaned up the edges, it's only the mortar on the back that stumps me. I've thought about attacking 'em with a cutting disk on the angle grinder, if they were the larger tiles I'd just go for it, but I'm not too sure about how to hold these li'l beggars safely.