D, what are you drying in the oven? Bowls? Figurines? I dry most of my pieces in the oven. Lowest setting. Overnight drying for bowls works most of the time, depending upon the thickness of the mache. To determine that I gently pry the bowl from its form. If it pops right off, it's obviously dry. If there is resistance, it hasn't dried completely.

Hope this helps!
karen
www.farroutart.com