3. A glue such as white glue (like Elmer's glue), and water
to mix with it 50-50. Also, a brush to apply the glue to the
cardboard (or a cloth or paper towel will do). Or, some may
wish to use a cheap "spray adhesive" available in spray cans.
You can also use wheat paste.
4. Three wire brads--or small nuts and bolts, or string to hold
the funnel together.
5. For a cooking vessel, I recommend a canning jar ("Ball"
wide-mouth quart jars work fine for me; the rubber ring on
the lid is less likely to melt than for other jars I've found.
A two-quart canning jar is available and works fine for larger
quantities of food, although the cooking is somewhat slower.).
6. The cooking jar (or vessel) should be spray-painted black on
the outside. I find that a cheap flat-black spray paint works
just fine. Scrape off a vertical stripe so that you have a
clear glass "window" to look into the vessel, to check the food
or water for boiling.
7. A block of wood is used as an insulator under the jar. I use
a piece of 2"X4" board which is cut into a square nominally 4"
x 4" by about 2" thick. (10cm square x 5cm thick.) One square
piece of wood makes a great insulator.
8. A plastic bag is used to go around the cooking-jar and block
of wood, to provide a green-house effect. Suggestions:
-Reynolds" Oven Bag, Regular Size works great: transparent
and won't melt. (Cost about 25 cents each in U.S. grocery
stores.)
-Any nearly-transparent HDPE bag (High-density Polyethylene).
Look for "HDPE" stamped on the bag. I've tested HDPE
bags which I picked up for free at my grocery store, used
for holding vegetables and fruits. These are thin, but
very inexpensive. Tested side-by-side with an oven bag
in two solar funnels, the HDPE bag worked just as well!
(Caution: we have found that some HDPE bags will melt
should they contact the hot cooking vessel. For this
reason, we recommend using the oven-safe plastic bag
wherever possible.)
-An idea attributed to Roger Bernard and applied now to the
BYU Funnel Cooker: place a pot (having a blackened
bottom and sides) in a glass bowl, and cover with
a lid. Try for a tight fit around the bottom to keep
hot air trapped inside. The metal pot or bowl should
be supported around the rim only, with an air space all
around the bottom (where the sunlight strikes it). Put a
blackened lid on top of the pot. Then simply place this
pot-in-bowl down in the bottom of the funnel--no plastic
bag is needed! This clever method also allows the cook
to simply remove the lid to check the food and to stir.
I like this idea - it makes the solar cooker a lot like
cooking over a fire. See Photographs for further details.
[Image: 02.jpg -- Photo description: This photo shows a Pyrex
glass measuring cup -- looking like it might hold one-half
gallon. Inside the measuring cup is a chrome or stainless
steel dish, fitting the sides of the cup very tightly.
The shiny dish is blackened on the outside and still shiny
on the inside. A man is holding the lid for the dish,
similarly blackened.]