Hmm...I have not had the problem of hardening and I have some for years. Maybe a couple drops of water? Test it...if you are going to toss them anyway, you have nothing to lose.
Keeping the lid tight isnt doing it for you? the plastic wrap sounds good. Are you keeping them away from heat sources including the window in summer?
If you decide to contact the mfgs-I would love to hear their answers.
|