How to raise humidity.

[maiden_canada]

hey ive had my bp for 6weeks or so and his last 2 sheds were good, but i got a humidistat/thermomter kinda thing and it shows the humidity at 60 when i spray down the cage, but it drops 20-25 after about an hour. hes in an aquarium i know they're **** for humidity but what can i do to raise it? he is on paper towel, has a large water dish and i covered half of the lid with a bath towel.

Thanks,
Clarke