How to rehydrate weed
A common dilemma facing weed smokers is weed that's too dry. Dry weed burns quickly and tastes harsh. It's no less potent though, so it's not the end of the world. We can also rehydrate it. We have the technology.
How to rehydrate your weed
Simply placing something damp in with your weed and letting it sit will transfer the moisture to your weed. Put a few drops of water on a cotton ball or a wad of paper towel, and leave it in the same container as your weed (though, not touching, since weed is hard to pick out of cotton). Check on it every hour or two, it doesn't take long. A good way to rehydrate weed is to tape a gauze pad to the lid of the stash jar, and add a drop of water as necessary; it works like a humidor, keeping your weed fresh and spongy.
How not to rehydrate your weed
Never use food. People often suggest putting bread or orange peels in your weed, though this is exceptionally bad advice. Food carries mold spores and imparts flavors in your weed. I've watched friends weep after losing ounces to mold within mere hours of putting orange peels in their weed. Don't let it happen to you.
All this can be avoided, if you simply take some precautions. Keep your weed in an airtight container and it will never dry out. See How long does weed last for more info. Also, note that weed should be stored in a cool dry place away from sunlight so that its potency doesn't decrease ( sunlight acts on the THC molecules and transforms them into a less potent variable )