Dehydrating tomatoes requires approximately 18 hours of drying time when sliced 3/8th’s of an inch thick. After making all that ketchup I was down to about 24 pounds of Roma tomatoes so I plugged in the dehydrator, broke out the mandolin (as in slicer, not the stringed instrument), and started filling trays with tomato slices. I can only dry about 28 tomatoes at a time so this should only take about 4 days.