O U T   I N   T H E   G A R D E N

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Hot Fun In the Summer Time

by Janice Austin,
Master Gardener

There is an old Phoenix boast that in summertime it is hot enough here to fry eggs on the sidewalk-well, it's true! You can! When you live in a city which receives more than 320 days of sunshine a year, it seems a shame not to take advantage of all that free energy. In June, The Urban Farm in Phoenix hosted a Solar Oven Workshop, where more than 25 eager chefs and gardeners gathered to learn how to make a solar oven and how to use it. Solar cooking has real appeal for multi-tasking gardeners who can be outside, simultaneously cooking and cultivating.

The solar seminar was timed to coincide with June 21st's Summer Solstice, when the sun moves to its most northern location over the Tropic of Cancer. Longtime Tucson desert gardener, Dan Dorsey, taught to a full house, which included a Hong Kong biology teacher, a German sculptor, a local public artist, an attorney, several landscape designers, organic farmers, Arizonans from Buckeye to Apache Junction, with more than one Master Gardener in attendance. We wanted to know what to do with all this sunshine!


Photo: Janice Austin

Dorsey, who has bachelor's degrees in Forestry and Photography, and is currently completing a Master's degree in Landscape Architecture at University of Arizona, talked about this Valley of the Sun having "the most concentrated solar energy in the world," providing "an energy that takes nothing away from the environment in its use."

He explained how easy it can be to get cooking with a basic solar oven constructed from simple materials costing a mere $18, capable of reaching 200-225 degrees. For those disinclined to make their own "Easy-Bake" solar oven, they More sophisticated commercial models range from Kerr Cole's $150 oven, which cooks between 325-350 degrees, and a $250 Sun Oven, which is capable of baking bread, heating up to 425 degrees. This "Sputnik-shaped" oven is far removed from the single reflector, cardboard box model constructed in the workshop, framed in sleek fiberglass, with four collapsible metal reflectors, a self-leveling tray and a convenient carrying handle.

To build a simple, inexpensive solar oven, each student was given a large, unassembled cardboard box, obtained from a mail delivery service for $4. The box was then assembled, top and bottom flaps overlapped into a closed position. 45 degree cuts were made on two parallel sides using a straight edge and box cutter, cutting all the way through. The box then was rendered into halves, flattened, and the top flaps cut off and put aside. Each half was reassembled, with the top flaps slipped into the overlapped base, which then were taped into place with duct tape. Next, the halves were combined, one inside the other, and a layer of newspaper was cut and inserted between all sides of the doubled box halves. Duct tape was used to seal all the open edges, including the bottom edge of the square base. Then, three metal brads were put through punched holes at the front edge lip of the square base, protruding 1". Next, the reflector was cut from a separate piece of heavy cardboard to fit over the box opening; one side of the reflector was covered with aluminum foil, shiny side up, and all edges then sealed with duct tape. At this point in construction, boxes were checked for a fit with the glass pane, which is supported over the oven by the protruding brads at the base; the reflector was then duct taped to the top of the oven, like a hinge, allowing the reflector to easily close and open. (As an option, one may paint the interior of the oven with nontoxic, black paint, to increase the heat.)

To use your oven, turn it to face south, showing no shadows inside the cooking area base; then raise the reflector up and look for a bright reflection at the center of the cooking area base-this will be at about a 30 degree angle-and then stake your reflector open at this angle, using a bit of wire. Remember to adjust your oven as the sun moves, keeping the foil reflection at the center of the base. If possible, this is done about every half hour. If not possible, face your oven due south and hope for the best.

TIPS FOR SUCCESSFUL SOLAR COOKING

• Use less water than conventional cooking, because your solar oven cooks at a lower temperature;
• By using covered glass or metal cooking utensils you can double the cooking temperature.

Solar ovens are an interesting project to do with children, culminating in a fun first snack, like baked apples or cookies. Remember to paint the exterior of your solar oven as part of the project. And be sure to take your solar oven camping, so you can cook without fire during this time of drought in the Southwest. And keep your home cooler by doing the cooking outside, saving money on your air conditioning.


Maricopa County Master Gardener Volunteer Information
Last Updated November 2, 2004
Author: Lucy K. Bradley, Extension Agent Urban Horticulture, University of Arizona Cooperative Extension, Maricopa County
© 1997 The University of Arizona, College of Agriculture and Life Sciences, Cooperative Extension in Maricopa County
Comments to Maricopa-hort@ag.arizona.edu 4341 E. Broadway Road, Phoenix, AZ 85040,
Voice: (602) 470-8086 ext. 301, Fax (602) 470-8092