build a solar oven

Although this is a simple project, it’s taking forever to get it done. Part of it is the recurrence of an old back injury, part of it is how bloody hot it’s been (perfect for solar ovens…), but most of it has been sloth on my part.

Today I’m cutting out the body of the oven and making up the foil/corrugated cardboard insulation.

I’ve been stumped on this last bit because I couldn’t think of a good way to adhere foil to cardboard without using some sort of contact cement. The last thing I want is chemical fumes from the adhesive to flavour my food! I’ve heard of using flour paste as an alternative so at least any fumes emitted would be non-toxic, but aluminium foil just is not porous so as to allow a good bond.

When I mentioned this to my wife she says, “Why don’t you just wrap the foil around the cardboard without glue?”

Of course, she is right.

I was trying to solve the wrong problem. I thought the problem was how to adhere foil to cardboard, when really all that needs to be done is for foil and cardboard to stay put relative to each other. Wrapping and crimping the foil will accomplish that much quicker, cleaner, and easier than anything I’d contemplated.

Who says you need an engineering degree to solve engineering problems? Sometimes, as in this instance, the degree can get in the way.

Alas…it just didn’t get hot enough to do anything. I’m going to have to build reflectors this winter.

I bought two pieces of 4mm glass to make two ovens, one piece 500mm square, the other 600mm square. The guy at the glass shop didn’t know what I meant by “double strength” glass (it may be an American thing), so I just got 4mm glass, instead of 3mm window glass.

It seems the stuff I want is “catering foil,” which is heavy-duty and not embossed. Now I just need to find out where I can get catering foil …

I’m going to build a Halacy-style solar oven, though I’m not going to use the rigid fiberglass insulation his design calls for. I reckon layers of pure radiant barriers will be more effective and cheaper.

The easy way to make reflectors is with aluminium foil. The trouble is, I have yet to find a store in Adelaide that sells heavy-duty aluminium foil; all I can find are lighter weight “embossed” foils. The embossing is a diamond pattern,and it’s hard to smooth the foil down to make refelector panels with it.

I got some silicone glue and wooden handles, had the box cleaned up with a friend’s router (and the friend), and the lid now fits perfectly. So painting the box with exterior grade paint and building reflectors so the oven get to 350 (right now, it will get to 270 or so, or so the plans say) or higher.

The glass arrived! The cover needed some more planing to make the glass fit, but it does now. I bought some wooden handles, and found some silicone adhesive to attach them to the glass. Next steps: attach handles to glass and paint the box with exterior-grade paint.

The cover is now built – a friend routed out a space for the glass cover. And I ordered and got a piece of tempered glass for the cover itself. I have to find some handles and strong glue adhesive. TOmorrow, I will assemble the box. The reflecters still need to be cut out and built, but technically, the box should be ready to cook tomorrow!

The outer box is assembled – it’s not pretty, but it is the right size. I needed some help from my husband to hold pieces in places while we nailed, and we needed to get different nails because the first ones were too weak. IT’s drying now.

One of the plywood pieces turned out to be too long – had trouble reading the printout. So I have to fix this.