cardboard box oven

[Stan Riddle]

If you're not sure about the number of coals to use, stick a meat thermometer thru the side of the box, and duct tape it to the side. Then, you can preheat your box just like your oven at home.

 

I've got one I've used probably 30 times, and the cardboard is still fine. I used coat hangers for a bottom rack, about three inches off the bottom, and another rack about 6 inches above that. I use an old round cake pan to put the coals in.

[KoreaScouter]

I've never run into a problem with the cardboard "breaking down" or failing from heat buildup. If the foil inside is intact with no breaks, and you've selected a good quality box to begin with, I don't think it would be an issue.

 

By "ugly" I don't mean burned up. Cardboard is porous and absorbent by nature. Anything that comes in contact with it is likely to be absorbed: dirt, bird poop, sweat, spilled coffee, what have you. Duct tape, on the other hand, is non-porous and water repellent. The aforementioned dirt, bird poop, sweat, spilled coffee, and especially the what-have-you, will wipe off no muss/no fuss. I wouldn't use foil on the outside -- even the HD stuff will tear through handling.

 

Regarding the door, I found I lost a lot of heat through the door, too. Without a door, I raise the box without tipping it, check whatever delicacy I'm preparing, then lower the box carefully.

Near zero heat loss.

 

I've introduced it into my units by using one myself, then sharing the end result with Scouts. Next campout, they want to try it themselves.

 

KS

[Scoutmaster Ron]

Great advice everyone, last night during my trial run it seemed that the heat generated by the coals ignited the bottom of the box and after hosing it down the aluminum foil was fine. I'll try the box that reams of paper come in next time.

[KoreaScouter]

Make sure all the cardboard is covered with foil if it's on the inside (or on the bottom if any heat is hitting the cardboard there, too. I actually roll the foil up under the bottom and an inch or so up the outside, then it all gets covered with the tape. I also carefully extend the tape along the bottom edge(lip?) of the box too. It'll get warm (quite warm, in fact), but hasn't combusted on me. If the charcoal's radiating straight at the exposed cardboard bottom, try a charcoal pan with some sides that will push that heat up instead of sideways.

 

I'm no expert at this, but I don't think the foil radiates anything since these coals are all ash-covered by the time I'm baking in the oven; in that regard, I think BW's correct. I think the role of the foil (no pun intended) is to serve as a heat insulator between the interior and the cardboard. Seems crazy that a think layer of aluminum could do that, but I've seen that it does.

 

KS

[Bob White]

Thanks KS,

For any non believers I found this column by a consumer reporter. She too talked with the folks at reynolds

http://www.nbc4.com/answerstoaskliz2002/1221937/detail.html

 

 

[ScouterPaul]

I am a great fan of box ovens. I've found that liquor boxes work best (the cardboard they use is a little thicker than most boxes). I've used duct tape but have found that furnace tape works better. I would advise that you purchase a name brank charcoal they seem to be more consistent.

[Wallace]

Yep...I don't use the dutch oven much anymore.

The boys have learned to bake rolls, cupcakes, muffins, biscuits, cookies, pizza, etc..

We have used the same oven for 2 years now and only just torched the cardboard this past weekend. I over heated it and was distracted with the rest of the meal.

Taping the foil with aluminum duct tape was the key to longevity.

[cheffy]

thanks for all the help. I think I can now build the ultimate box oven. What with the racks, door, stand, coal pan, and thermometer this thing has more bells and whistles than my car.

If only I could pack in some sheet metal and a welder I could have a really nice oven.

[packsaddle]

There are a couple of factors involved with the success of the design. 1] containing a hot fluid (the air) and 2] the reflective foil lining.

The first factor is why doors and even very small holes cause difficulty. It is useful to think of the oven as a bucket. If you filled it with water and it had leaks, then air will probably escape even easier. The foil helps with #1 but also 'reflects' the radiant energy of the coals allowing the air much greater opportunity to absorb that energy and increase in temperature. The reflective action also helps protect the paper from reaching combustible temperatures (great book also, BTW). FOG, you are correct about the energy being IR but remember, you 'see' the foil using VISIBLE wavelengths. Unless your eyes are different from everyone else's, you have no idea - using your eyes alone - of how well the foil reflects IR. Your uncontrolled experiments at home are possibly biased.

[Fat Old Guy]

" FOG, you are correct about the energy being IR but remember, you 'see' the foil using VISIBLE wavelengths. Unless your eyes are different from everyone else's, you have no idea - using your eyes alone - of how well the foil reflects IR."

 

Unless I've forgottem all of the E&M stuff that I learned back . . . well, back then . . . shiny reflectors reflect more EM radiation than dull reflectors. How much more is a matter of wavelength but the IR wavelengths are close enough to visible that it shouldn't be that different.

 

Maybe we should ask Cheffy. In the meantime, I'm off to the lab with some thermocouples, a heat lamp and my DMM.

 

 

[cheffy]

Here's my thoughts. Corrigated cardboard is a great insulator and the foil is just a protective layer so the box doesn't go up in flames. With all the variables present in most regular over not just cardboard, the foil side would not matter. Not that I've tried but I would guess that the difference in degrees would be very slight. If I have time in the next few weeks I would be curious enouge to try the heatlamp with the IR thermometer experiment. Could be a great science fair project for some young Scout.

[packsaddle]

While I admit that I don't have the data on IR reflection and FOG's memory very well could be correct, I was merely making the point that visual observations of something that we can't see...may be unreliable, DUH! However in practice, another close relative is microwave radiation. Take at look at the variation of reflective surfaces on satellite dishes. I observe a wide range of successful applications: new shiny ones, new dull finishes, older finishes in many conditions...just to add to the list of unscientific observations.

Cheffy, I think you're probably right, any real difference would probably be negligible, especially in a foil-lined cardboard box.

As a followup, anyone out there believe that a tray of hot water will freeze more quickly than an equivalent tray of cold water if both are subjected to identical freezing conditions?