Ah!
1. Nice humi!
2. Get those cigars into ziplocks!!!
3. the Xikar stuff is super-absorbant-polymer gel. Nothing wrong with SAP, but that isn't enough SAP for that humi IMHO. I would use at least another jar.
4. As I presume you don't have a fan going in there (like an Oust fan), the jar has to be in the tray. As a general rule, active humidification goes on the bottom, passive humidification goes at the top.
5. The humi looks to be veneer, and you've sealed all the glass, so full seasoning is not needed. However, the protruding lip on the lid (see black arrow in pic) does need to have sufficient moisture to expand. A very even wipedown with distilled water is needed. Too much and you'll have to pry the humi open the first time.
6. Does the hygro have a clear gasket around it (see arrow in pic). I've seen these clear gaskets get misaligned and not seal all the way around.
7. Finally, if the book/weight idea doesn't work, a thin rubber seal (see green line in pic) will do the trick. I use closed-cell neoprene rubber weatherstripping tape found at a home improvement store, but anything similar will work. Get the thinnest possible, usually 1.5mm (3mm max). The problem area is usually between the two hinges at the back, but you might as well go all the way around. You may need to put a book on top to get things to seat.
Good luck!
Bookmarks