Wash, peel (optional) and core apples.
Slice apples thinly and evenly (1/4 inch), use a mandolin if possible.
If desired, dip slices in anti-browning solution of 1/4 cup lemon juice in 1 quart of water.
Remove slices from water and pat dry.
Sprinkle slices with a light dusting of cinnamon.
Arrange apple slices on wire baking or cooling racks and position in oven. Or position apples directly on clean oven racks.
Set oven at the lowest temperature, about 150°F (65°C) and prop door open with a wooden spoon to allow for air circulation and moisture to escape the oven.
Bake for 5 to 8 hours. Times vary due to humidity levels, ovens, apple varieties, slice thickness, etc. Just keep checking.
Check apples for any moisture on outside and inside. The slices should feel dry and leathery without any tackiness. Rip a slice in half to see if there is any moisture on the inside - it should look like a dry dense sponge.
Allow to cool several hours before storing in an airtight bag or container.
Store in a dry, cool, dark place for several months, if you don't eat them all! If you're unsure about their dryness store in a freezer.
Case hardening occurs when the outside of food dries so quickly that moisture from the center is unable to escape due to drying with high heat. Therefore, very low temperatures are recommended for drying food. However, if you're planning to eat all your apples right away, go ahead and turn up the heat to dry the outside.