@Brian-Spooner about 400 kg/cubic meter or about 25 lbs/cubic foot. And yes I used water displacement. High tech tools- A garbage bag to "protect" the block a 30 yr old food scale to weigh the block an empty Kitty Litter pail that holds about 6 gallons a measuring cup to determine how much water was displaced. I checked the scale by weighing a half gallon of water (~4.2lbs, a US liquid gallon of water weighs about 8.34 pounds at 17°C ) I filled the bucket to the rim until it started to overflow put the bagged block in forcing it down to submerge it, and and let the water overflow refilled the bucket measuring water to refill known problem areas - the volume of the plastic bag, accuracy of the scale, compensation for temperature and probably many unknown problems. But my blocks didn't come out perfect cubes and I wanted to get some measurement of density before I went on a trip.