How to Design a Drying Oven

Hunters, fishers, gardeners and gatherers have been preserving food by drying it for centuries. Most of the time their method was simple: for example, hanging meat over a peeled branch and placing the branch above a smoky fire or out in the noonday sun. Drying food remains a practical and convenient way to prevent spoiling when food must be stored for days or months, and a couple of cardboard boxes, some plastic wrap and tape will construct a simple solar dryer.

Things You'll Need

• Long, shallow cardboard box
• Deep cardboard box
• Disinfectant wipes
• Heavy-duty scissors
• Small sturdy knife
• Black paint or black plastic bag
• Clear plastic wrap
• Scrap lumber, thread spools, or small cups
• Pair of sawhorses
• Duct tape
• Plastic screen
• Nylon net

Instructions

Make an Inexpensive Temporary Solar Food Dryer.

1. Cut several 1-inch holes in both ends of the long box with a utility knife or scissors. Completely line the bottom and sides of the box with black plastic cut from a bag or paint the interior black. Allow the paint to dry or the black plastic to air for several hours before covering the box. Cover the top of the box with clear plastic wrap, taped securely to the sides of the box. Set aside.

2. Cut l-inch holes in one side of the deeper box and set the box on sawhorses or on a small table. Lean the shallow box against the side with holes of the deeper box. Arrange the shallow box so that it faces and collects the maximum amount of sun. The bottom edge of the shallow box will rest on the ground at an angle.

3. Build an air duct between the deeper box and the shallow box using scrap pieces of cardboard and duct tape. The holes on the two boxes do not have to align as long as the passage of heated air is maintained between the two boxes.

4. Build a low platform using empty thread spools, scrap wood or small cups within the deeper box to support a plastic mesh screen. Place the food to be dried on the screen. Cover the deeper box with a layer of nylon net to prohibit insects.

5. Experiment with lengths of time to dry different foods. There are dozens of variables that can affect the optimum dehydration time including the type of food, the climate, the thickness of the food and much more. Record the most successful experiments in order to repeat them if desired, or discard the dryer.

Tips & Warnings

• The cardboard boxes used should have clean interiors, but they do not need flaps to cover. Wipe them out with a disinfectant sheet before beginning.

• Buy plastic mesh sheets at a craft store. They are sold for making craft projects using yarn. They are ideal for dehydration because they can be washed and are fairly rigid. Other screen materials may also be used but do not use ordinary window screen unless it is plastic. Some materials may have toxic coatings.

• Nylon net is always available at a craft or fabric store. It can be washed and usually contains no toxins. The plastic mesh might also be used on the top of the drying box but probably won't be large enough without taping pieces together.

References

• Mother Earth News: Do It Yourself Recycleable Solar Food Dehydrator
• Solar Cooking Wikia: Solar Food Dryers
• Countryside Magazine: Drying Food with the Sun