When the ambient air is dry, the voltage seems to drop on these crystal cells. If I put a drop or two of water they immediately perk up.

Today I measured the voltage on #4 and #5 crystal cells and they were at 1.15 volts and 1.03 volts respectively.  After adding a couple of drops of water to the top of the cells, the voltage climbed to 1.41 volts and 1.30 volts.

When I checked about 10 hours later, the voltage on #4 was  1.37 and on #5 the voltage was 1.36.  That seems to be a pretty typical crystal cell voltage with no load.

I thought that if a little moisture increased the output like that, perhaps more moisture would improve the output even more. Well, not so much.  I added a few more drops of water to both crystal cells  and the voltage dropped about 1/10 of a volt on both of them.  It climbed back up after a few minutes but no higher than normal.