I have a simple glass jar type humidor that I use at work. For the last couple weeks, I was using a salt / water solution and it kept it around 70 %. I wanted to do better so I replaced that with a 50/50 water prop glycol mixture on a sponge in a soap dish. Now I can't keep it under 75% for the last couple days. What did I do wrong?? Too big sponge??