I use coir for some bulb growing media so I had planned to do this test also. Mike and I are converting your 1 L tests to add them to the chart. Your point abut the coir block needing to be expanded first is important. Yes the test is based on volume and the water 1 ml = 1 g equivalent. My own experiment is in the re-dry stage. I am also concerned about salt so I soak and pour-off water three times before using coir. I see the SERAMIS is equivalent to the non-clumping kitty litter or Akadama or Turface. I have not tried those. Hans-Werner Hammen wrote: > If I reconstitute COCO from Coco-Block, and let the loose substrate re-dry, then it will shrink but almost negligibly.When I put 1 Liter of this dry substrate into a pot, the bottom and drainage holes respectively covered with a net (so no substrate will escape after rinsing) WEIGH it before and after RINSING and DRAINING thorougly, the whole container will become 500 grams heavier. > BTW 1 Liter of dry SERAMIS, in the same "experiment" becomes 250 grams heavier. Everybody can (try to) verify the Results for themselves.I am curious whether anybody will obtain conspicuously different results xD