I don't normally post as someone usually covers it, but allow me a moment... As a Cigar smoker, allow me to add 'a few cents' in....Rockwool? I'd rather recommend Oasis Foam, as used by Florists for FRESH arrangements. You need the Wet/Water foam, and not the dry arrangement foam. You should be able to find this in most crafting stores, and is probably cheaper. And "soaking" it would be wrong as well. By soaking the brick, you will leave no room for the absorbed moisture. Besides, I would also vote against this as, even though it will work, it will only be beneficial until full - then the water will puddle out and be capable of evaporating back into the air. This method is best suited for ADDING moisture to the air, versus taking it out. Salt: For the salt to work, it must maintain a 'mound' for the surface area to absorb moisture. And yes, that is a steady 75% - we use it to check the accuracy of our Humidification gages. ============ Just my two cents from my cigar experiences.