Complex sentence: Drying involves using air and/or heat to remove water from the paper sheets; in the earliest days of paper making this was done by hanging the sheets like laundry; in more modern times various forms of heated drying mechanisms are used.
Split into simpler sentences: Drying involves using air or heat to remove water from the paper sheets. In the earliest days of paper making, this was done by hanging the sheets like laundry; in more modern times, various forms of heated drying mechanisms are used.