Multiple Hourglasses Expose Variations

These commercial hourglasses purchased at a home interior store were labelled 30 minutes, but visually the amount of sand varied....at least when eyeballing the amount of sand inside the glass bellies. Upon timing them with a stopwatch, it was found true that the times are all different by as much as a minute or more. They were put in order, left to right, by time. The finished multiple hourglass unit combining all four will have to be named something akin to 30 Minutes, Give or Take!

Left to right: 32 min., 11 sec.; 31 min., 45 sec.; 31 min., 40 sec.; 29 min., 45 sec.