Unpolished=bad. And we can toast bread.

Today Elliot and I tested the oven with the unpolished aluminum panels that we installed with the tensioning system last time.  They are ineffective.

Here are are timings and temperature measurements (Fahrenheit):

0:00 -- 79
1:00 -- 80
2:00 -- 80
3:00 -- 81
4:00 -- 81
6:00 -- 81

Close-up of polished panels installed on top of unpolished panels.

This is very disappointing, but accords with the subjective "hand test"---I could hold the palm of my hand at the target area for 25 seconds, which is longer than the others.  We then installed our mis-cut polished panels that have a near-mirror like surface.  The "hand test" lasted to a count of 13.  Here is the time measurement:

0:00 -- 92
1:00 -- 93
2:00 -- 94
3:00 -- 97
4:00 -- 98
5:00 -- 99
6:00 -- 100
7:00 -- 100
8:00 -- 100

Note that we adopted an experimental procedure of "stirring" the 2 cups of water with the thermometer, which made our temperatures much more stable.

We went inside for approximately 30 minutes to plot our next course of action, and when we returned the water was at 130F (we took it out and measured it very reliably.)  At this point, the oven was not aimed particularly well due to the apparent motion of the sun.  This was basically the same performance we got previously with the same miscut polished panels.

Our conclusion is: we really need to create properly polished, properly cut panels and test them.  That will be my mission for this week.

We performed two other interesting experiments.  We took 3 panels of posterboard that had foil glued to them via 3 distinct mechanisms: contact cement, rubber cement, and heated rubber cement.  We curled them (with tape) and left them in the sun.  All three developed some wrinkles.  The heated rubber cement seems to have the fewest wrinkles.  We bought some much stiffer poster board and Elliot is going to manufacture some new panels for us to test with additionally, in hopes of doing a side-by-side test of foil-on-board vs. polished aluminum.

Close-up of one of the panels

Cold rubber cement--large wrinkles.

Our three foil-covered posterboard panels, heating in the sun---showing developing wrinkles in all cases.

Finally, we stuck a piece of bread in the target area, aimed it, and left it alone.  We went back about 45 minutes later (we weren't really tracking time closely.) The oven had toasted the bread to browning, at least in some of the region. (Note that our target area is a 3" x 3" square, significantly smaller than a slice of bread.

Our toasted bread.

 It isn't visible but the whole 3" square was dry and staled (that is dehydrated---what we think of as toasted.)  Obviously, the burned part received more intense solar radiation.  Here is the back of the same slice, with the browning showing through.

This is, in fact, the first thing that we have eaten which we "cooked".