Monthly Science: Basement Safe Silica Gel Equilibria

A month ago I tossed a new bag of silica gel into the basement safe and put the used one on the workbench to see how much more water it would adsorb. The numbers worked out like this:

  • Bag + staples: about 8 g
  • Dry weight: 500 g of silica gel beads
  • At 24%RH: 575 g = +67 g water
  • At basement ambient, about 50%RH: 652 g = +144 g water
  • At upstairs ambient, about 65%RH: 673 g = +165 g water

Referring to the Sorbent Systems charts

At 50%RH, the capacity is about 27% = 135 g of water, which is close to the measured 144 g. The logger recording groundwater temperature says the average humidity hovers just under 55%RH, in which case 28% capacity = 140 g of water: as close as you could possibly hope for.

At 65%RH, the capacity is about 32% = 160 g of water, which is very close to the measured 165 g.

The safe humidity remains flatlined at the logger’s 15%RH minimum level, with one blip when I installed the door gasket strips:

Basement_Safe - 2013-08-28
Basement_Safe – 2013-08-28

After I accumulate a few more used bags, we’ll see how well they regenerate.