Make a Wonder Bag/Wonder Oven Thermal Cooker

As I mentioned in yesterday’s post, I learned about commercially manufactured thermal cookers in a food storage class at my friend’s house.  I checked them out on Amazon and then I somehow found a company that makes Wonder Bags for thermal cooking. 

“Hmmm…,” I thought, “that looks pretty similar to my Wonder Oven, but with an updated name and design.” 

Wonder Oven

I made my Wonder Oven way back when we lived in Missouri using fabric I already had on hand and the pattern at the address below.  I only had to buy the Styrofoam beads.  The only hassle with this pattern is that you have to draw and measure it yourself using the dimensions and angles provided in the directions.  You’ll have to find a newspaper or maybe use a roll of gift wrap or tissue paper.  It’s all straight sewing and not too difficult, but the pattern is only one size, and you have to hope your pot will fit well in it. 

Wonder Bag

I remembered well the bit of a hassle with making my own pattern pieces for the Wonder Oven and felt that making my own Wonder Bag would be easier. I picked up a fitted flannel sheet at the thrift store for a dollar or two, cut off the elastic, and folded it in half.  I wanted to be able to bake large loaves of bread, which meant the Wonder Bag would have to be large enough to hold my stock pot.  Here are the basic directions:

Place your chosen vessel on the folded fabric/sheet and draw a circle about 1.5” larger than the bottom of the pot.  Pin the top and bottom together and stitch on the line, leaving about a 2” opening through which to insert the stuffing.  Stuff the bottom and stitch opening closed.

Measure the height of the pot, plus about 4” for folding over the top and draw a larger circle around the first.  (For example, if my pot was 8” high, I’d add 4” to that 8” and draw a circle about 12” larger around the first circle.)  Pin the top and bottom together.

Next, draw about a dozen straight lines from the first circle to the outside circle, radiating as if from the center like spokes on a wheel.  Stitch along these lines, stopping about 2” before the edge.  Trim 1” from the edge all the way around the upper circle.

Now stuff each section, pinning or stitching each section closed as it is filled, depending on your filling material.  If you are using wool, as I did, pinning will be fine.  If you are using Styrofoam beads, you’ll have to stitch each section closed right after you fill it. 

If the top and bottom have not yet been stitched together, do so now.

Fold over the edge of the bottom circle (which is the outside) ¼” and hem it.  Then fold the hemmed edge just over the cut edge of the upper circle and pin in place.  Stitch in place to form the casing, leaving a 2-3” opening. 

Measure a thick piece of yarn or twine the circumference of your bag and use a safety pin to thread it through the casing, knotting both ends.

Make a pillow top for your Wonder Bag by placing the lid of your pot on the remaining folded fabric or sheet and draw a circle about 2” larger around it.  Pin these pieces with right sides together and sew around the edges leaving about ¼” seam allowance and a 3” opening for turning.  Turn the pillow top right side out and stuff.  Stitch the opening closed. 

So now that I have one each of the Wonder Oven and Wonder Bag, I can fairly compare the two.  And I think I like the Wonder Oven a little bit better.  While it does take longer to start sewing the Wonder Oven due to having to make the pattern, it’s a bit easier to assemble.  Because there aren’t any channels like with the Wonder Bag, it’s easier to make the Wonder Oven conform to the size of your pan.  The Wonder Oven is a bit more forgiving in that respect. 

Because the whole bag of the Wonder Oven is being filled at once, that step goes a lot faster than filling each individual channel and then sewing each section closed one by one. 

With the Wonder Bag, the pillow top has to be carefully placed on top of the bag and then snugged into place while the bag is being cinched closed.  That takes a little more effort.  When using the Wonder Oven, the pillow top is quickly placed on the pot. 

Bottom line:  They both work pretty well. 

Now it’s time to make a few notes about material options.

Make sure to use 100% cotton for the bag or oven.  Synthetics or blends will melt at temperatures much above 350°F, and maybe even at lower temperatures.  The same goes for the stuffing if anyone in your family has a sensitive nose.  While Styrofoam beads make for a bag/oven that conforms well to the pot, they will also release fumes the first couple of times the bag/oven is used.  My kids found the odor quite objectionable.  But now that it’s been a few years and we’ve used the oven a few times, we don’t notice the odor anymore. 

Links to related posts:

Global Sun Oven

Thermal Cooking

References:

Wonder Oven pattern and sewing directions:  http://www.iwillprepare.com/cooking_files/Wonder_Box.htm

http://foodstorageandsurvival.com/building-a-wonderbox-style-insulated-cooking-box/

https://foodstoragemadeeasy.net/fsme/docs/wonderbox.pdf

https://www.instructables.com/How-to-Make-a-Wonder-Box-CookerCooler/

https://www.allselfsustained.com/how-to-make-and-use-a-wonderbag/

https://seasonedcitizenprepper.com/bevs-thermal-cookeroven/