Building a Solar Oven, Part 1

My materials:

  • two cardboard boxes in good shape, one a couple of inches larger than the other on all sides
  • aluminum foil
  • spray adhesive (can also use diluted white glue)
  • dried grass clippings
  • a few other various pieces of cardboard
  • turkey-sized baking bag (can also use clear Plexiglas or glass, two layers are ideal)
  • wire clothes hanger
  • flat black grill paint
  • probably some Duck tape (duct tape)

With our recent move, it was surprising to me how hard it was to find the two perfect boxes for this project.  The inner box is the oven itself, and the outer box provides insulation.  You don’t want boxes that are too deep, but your outer box still needs to be large enough to accommodate the oven box.  When it came down to it, I had to decide between an oven box that was shallow but of a nice length and width, and another box that was deeper, but not as long.  I chose the shallow box, and decided to modify it so that the flaps would stand up rigidly and provide more depth.

First, I closed the larger box and centered the oven box on top of it, and then traced around the oven box.

Tracing around the smaller oven box onto the top of the larger outer box.

Yes, I did have a large box devoted to hangers.  Didn’t you?  And… I have never had Direct TV… where did that box come from?

Next, I cut all the way through all of the flaps with a mat knife (box cutter).

All layers of flaps cut through, and I have them weighted down to show you the resulting hole. Unfortunately, I forgot to take pictures until I was several steps along, which is why the inside is already shiny. :)

Then I opened the box and applied foil to the inside, using the adhesive spray.  It isn’t absolutely necessary to foil the inside of the outer box, but it reflects more heat back inside, making the oven more efficient.  White school glue diluted to half strength can also be used to apply the foil, but I didn’t want to deal with the difficulties associated with applying and using it.  And… the spray adhesive will adhere the foil better, as well.  Not very important for the outer box, but for the inner box, which will get more wear and tear as the oven box, having the foil stick as well as possible is a good thing.  The spray adhesive was about $10.  It was the more expensive of two spray adhesives available by 3M at Wal-Mart, but it was a larger can, and was the only one that mentioned gluing foil.

I applied foil to the inner flaps instead of the outer ones, forgetting that they don’t meet in the middle.  So I have applied foil to the part of the outer flaps that bridges the gap.  Should be good enough, but I’ll remember that if I ever build another one.

I have since added some more foil to close the gaps in the corners and along the flaps.

There’s less trouble with keeping the foil shiny if you spray the back of the foil and apply it, rather than spraying the box.

My oven box wasn’t as deep as I wanted, so I cut some cardboard strips from extra material and bent them.  To get them to stick and do their job, I needed the strongest possible bond.  This was accomplished by spraying both the strip and the corner on the box, and then waiting half a minute.  When pressed together, the adhesive acts like a contact cement, and bonds quite well.  I did have to go back around when I was finished and hold each one for a few seconds again.

I will probably reinforce the corners with Duck tape all the way around, to make sure I exclude air from outside. I'll concentrate on the added flap supports, to prevent them from popping off, just in case they're tempted to.

Then, I applied foil to the inside of the oven box, using smaller pieces so I could keep them a bit bit flatter for better reflection.

I think I ended up with two layers of foil over most of the surface.

Tomorrow, I hope to get a good bit of assembly done!  :)


Comments

Building a Solar Oven, Part 1 — 4 Comments

  1. I just love your posts on being self sufficient. I think I’ll have to make one or 2 of these! Thanks for posting the pics :)

    • Thanks, Iggysbabysitter! If this works well, I might end up with two or three of them myself. One baking bread, one cooking dinner…

      I have a big piece of glass, and I was going to stick the so-far oven out in the sun with a thermometer in it and the glass on top, just to see how hot it would get unfinished and with no reflector. I don’t even know if the top is even enough for the glass to sit on properly… it might not get hot at all! But then it decided to rain today, and that is the big key to a solar oven… you really do need the “solar” part in order to get anything accomplished. LOL

      I have the base finished, and need to post about it. I need to make the lid/reflector next. I’m having trouble finding a large enough, unbent piece of cardboard. My uncle says he has some at work, though, so hopefully I’ll have a piece in the next day or two if he’s able to go back to work (he’s sick).

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