While water-only humidity trays are pretty much useless, saturated salt trays are not! The rH over a box of kosher salt and water in a closed container is 75% over a pretty consistent temperature range. https://www.engineeringtoolbox.com/salt-humidity-d_1887.html (Photographers use this trick to keep paper moist for hand-applied emulsions.) Other salts can get the rH even higher, but salt is easy to come by. And because the salt concentration is insanely high, nothing will ever grow in it, so you can pretty much use the same tray forever.
I use something similar to humidify my puer! Boveda sells salt packs that keep a confined area at a given RH by releasing humidity and absorbing it when the surroundings get too high.
While water-only humidity trays are pretty much useless, saturated salt trays are not! The rH over a box of kosher salt and water in a closed container is 75% over a pretty consistent temperature range. https://www.engineeringtoolbox.com/salt-humidity-d_1887.html (Photographers use this trick to keep paper moist for hand-applied emulsions.) Other salts can get the rH even higher, but salt is easy to come by. And because the salt concentration is insanely high, nothing will ever grow in it, so you can pretty much use the same tray forever.
I use something similar to humidify my puer! Boveda sells salt packs that keep a confined area at a given RH by releasing humidity and absorbing it when the surroundings get too high.
LOL I use those packs for my weed, 62%. What's the best rH for tea?
Lots of blood spilled on forums about that very question. I use 72%, now researching ways to add heat.