Solar Cooking Archive Discussion Forums

oloh_151 · Joined: 22 Apr 2008 Posts: 1

so i call mine the frankenstein, and i need help with it. its a box cooker. its about 3 ft by 2 ft big. with 3 reflector pannels to catch the sun. when i first made it, i had only one and that barely seemed to heat it up. i added the two to the side and that helps. the inner box is lined with foil to reflect the heat aswell. inside is a small black rubber inner tube from a wheel barrow and a black metal plate. the pot sits on this (the bottom of the pot sits on the plate and the inner tube sort of surrounds the base of the pot). the pot has a black metal lid. to cap all this off, there is a glass plate over the box, to retain the heat.

so my question is how to i get my oven hotter. i think it looses heat to quickly. i tried to cook rice and it over cooked the outside of the grain, but left the inner crunchy. this makes me belive that it cooked too slowly at a low temperature. i couldnt cook the rice any longer because it was already turning to mush, so i had to take it out. so i ended up with sort of half over and half under cooked rice.
one thing i thought it might be is the lid of the pot needs to be glass, to allow more heat in? or my insulation of the box is poor, so the hear escapes to quickly and doesnt heat the oven up enough? maybe my box is too deep? its a little over a foot deep.

anyway. does anyone have any suggestions for the frankenstein? i am currently in a small mexicn village, so i cant really just go out and buy stuff that easy. things have to be found on the farm (hence the reason why there is a wheel barrow inner tube)

thanks. olly

SharonID · Joined: 24 Jun 2007 Posts: 74 Location: northern Idaho

You don't say, but is your oven constructed of two boxes with insulation between the two? Anyway, more insulation might help (crumpled newspaper, dried cornstalks—almost any material that is dry and can be packed or crumpled to create lots of air spaces). It also might be that your oven is too deep. If it is deeper than it needs to be for the pot(s) you are using, add some pieces of cardboard underneath the steel/tube/pot to make it shallower (or if you are fortunate enough to have a flat-ish box that can fit in your oven, you can foil that and use it when you want the oven to be shallower). I did that in one of my paper-box ovens, so if I am using a shallower pan I can have a shallower oven that gets hotter.

Another thing I find can really make a difference is to make sure that the back reflector is wider than the opening of the inner box. My box oven gets a real boost from a front booster panel I sometimes use. It's just a piece of foiled cardboard, a little longer than the oven and maybe ten inches wide. I prop it on a half or quarter log, using a couple of flat, foiled rocks to help hold it in place, aiming it so I can see the light from the booster hitting the back reflector. I have watched the thermometer visibly move sometimes, after a good placement of the front booster, and since the log support is curved, I can change the angle as needed. Aiming the back panel can make a difference, too. Make sure it is directing as much light as possible into your box. Another thing that can help, if there is going to be space in your oven that is not taken up by pots, is to put two or three fist-sized (give-or-take) rocks (dark, if possible, but you can dust them with spray paint if they are very light) in your oven to help hold the heat. And preheat your oven before cooking whenever possible.

I don't know about the inner tube. While it's true there is a way to cook in an inner tube, if the fit with your pot is so tight that it is keeping the light from hitting major portions of the pot and steel, it might not be helping. I'm not sure though, but you might try it without the tube as well as with it. If you don't want to risk wasting food in some of the experiments, just trying to boil water will give you a lot of information.

When cooking rice or quinoa or other soft grains, you will get a much better result if you get the water very close to boiling before you add the grain, and it might help to preheat the grain as well (maybe not in the oven... you don't want to toast the rice, but you could so something like put it in the sun in a small dark pot or can while waiting for the water to heat). You will be much less likely to get that soggy outside/crunchy middle if the water is hot when you add the rice (this is even true on the stove, at least for long and medium grain rice, but it is even more important in solar cooking)

You're on the right track though, and asking good questions. Good for you! Keep experimenting and don't give up. If I can make this work up in the north where I am, you can do it so much closer to the sun! People are rigging up ways to suncook with all kinds of materials, all around the world, so hopefully you will find the combination that can work for your situation if you just keep at it. Smile

Regards,
SharonID
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