The moisture you are noting is actually caused by decomp. When the wood is compressed (as in freshly cut then bagged and stacked) it decomposes and releases moisture and heat. This is what warms your tank at first and provides humidity.


Once the wood dries out this means all the moisture has left the wood. As you have discovered spraying or soaking the wood just gets it wet it doesn't re-moisturize the wood.

I am not aware of any way to re-hydrate the wood without inducing a lot of mold into the equation.