boil water in the room and it would go up=]
haha so would you room temps. Well maybe not you may have a huge room and an amazing vent setup, but if you have a small grow thats a poor choice. Also the electric bill to run even a hot plate for any duration of time can be quite expensive not to mention the safety factors that you are disregarding by leaving an open heat source running for that long. I'd say your best bet would be to get a standalone humidfier. If you want to not raise the temps in the room and still add humidity get a cool mist or ultrasonic humidifier as they do not use heat to create the humidifying mist.
As a side note I've tried many things before i finally made the choice to add humidity with a humidifier. I tried the bowls of water, and sponges with fans blowing on them and etc. I even tried making a large paper towel wick to place into the bucket of water to help. They all gave rather mediocre results by only raising my humidity 5% or so. If you really want to add consistent substantial humidity nothing beats a good humidifier.
I found mine at a thrift store for 6 bucks and its an ultrasonic to it was pretty much a steal. I know you can pick up a pretty cheap cool mist humidifier from Vick's at most local super stores for really cheap, i think under $20. You will have to deal with adding water to the humidifiers reservoir every day or two so attribute for that when you're buying one and placing it in the grow. Good luck let me know if you have anymore questions.
