From your videos it looked as though the walls of your mortars might not be thick enough to withstand repeated grinding events. Even stone mortars are very thick.
The most functional home mortar that I've seen was shaped like a dog's dish with a wide flat bottom so it couldn't be knocked over. It was small enough to rest the weight of a hand and body on while the other hand did the grinding. I don't know how long it lasted but it sure was user friendly. I've never seen another one like that.
From your videos it looked as though the walls of your mortars might not be thick enough to withstand repeated grinding events. Even stone mortars are very thick.
The most functional home mortar that I've seen was shaped like a dog's dish with a wide flat bottom so it couldn't be knocked over. It was small enough to rest the weight of a hand and body on while the other hand did the grinding. I don't know how long it lasted but it sure was user friendly. I've never seen another one like that.