I do it a very inexpensive way. I got a cheap humidity guage on Ebay which is about the size of a calculator and reads both the humidity and temperature. Then I got a big plastic storage bin from the local home store (got mine at Lowes) and made a wood frame with a fiberglass screen slightly larger than the inside bottom of the storage bin. Since the bin sides are slightly tapered, the screen sits about 2 " above the bottom of the bin. I put about a gallon of warm water in the bin, put the paper on the screen in the bin, put the humidity guage inside the bin and put on the top. It only takes the inside of the bin about 15 or 20 minutes to get up to over 60% humidity. The warmer the water, the faster the humidity raises. Note that I live in the Desert South West where humidity is very low most of the year.