My original intention was to make dried pears. Because I dried the pears at 225F, I ended up with pear chips... still delicious.
Now I know the proper way to make dried pears (and dried fruit in general). Cut slices between 1/8 and 1/4 inch thick. Soak for 10 minutes in a solution of water and ascorbic acid (ie: vitamin C - crushed vitamin tablets supposedly work). The ascorbic acid is an anitoxidant, and prevents discoloration. You have to use a VERY low temperature - ideally between 130F and 140F. Prop the oven door open with a wooden spoon. Dry for around 6 hours, until a leathery texture has been established.
I used bare oven racks to maximize surface area (and to avoid flipping), but found that many of the slices fell to the bottom of the oven, where they charred. One website recommends covering the oven racks with cheesecloth; I'll have to try that next time. Also, because I have a gas oven that is heated from the bottom, those pieces on the lower rack were exposed to higher heat. It's probably best for me to stick to the high portion of the oven.