SUL Freezer Bag Cooking Cozy - Part 2

In part 1 of this article I talked about an idea I had to reduce the weight of my freezer bag cooking (FBC) cozy. I basically made an envelope out of an emergency blanket thinking that the reflective material would hold the heat inside the cozy while the meal "cooked". In addition, I would place the cozy inside the cuben fiber stuff sack (which I already carry to contain my cook pot) with the thought that this would add additional insulation to hold the heat in similar to how a wind shirt holds your body heat in. This is the point where I test my theory...

Pictured below from left to right are the trailcooking.com FBC Minimalist Cozy,  the traildesigns.com Caldera Keg-H Cozy, and my SUL Cozy prototype. I decided to put these through a series of tests to compare my unit to others I have used.

 

For the testing, I placed 1/4 cup of couscous inside a quart size freezer bag, added a thermometer, and then 1/3 cup boiling water. I pushing most of the air out of the freezer bag, sealed it, then closed the cozy. I placed the cozy inside the 42 degree  Fahrenheit  refrigerator and set a timer for 10 minutes (the longest wait time for a FBC meal is usually about 8 minutes). I then recorded the temperature at 2 minute intervals with various minor changes. The chart below shows the results of the testing...

Minutes	FBC Minimalist Cozy		Trail Designs Keg-H Cozy w/cup	Trail Designs Keg-H Cozy w/o cup	SUL Cozy inside cuben stuff sack	SUL Cozy inside cuben stuff sack on top of pot lid	Cuben stuff sack only - on top of pot lid	Cuben stuff sack inside of Evernew .6L pot & lid	No cozy
	1.15oz		1.85oz	0.7oz	0.05oz	0.05oz	0.0oz	0.0oz	0.0oz
2	146	171	160	168	164	167	155	156	163
4	136	165	158	167	153	158	144	145	152
6	129	158	157	165	145	152	135	140	144
8	123	153	155	162	138	147	128	135	137
10	119	147	152	158	132	142	123	130	131
Dif	27	24	8	10	32	25	32	26	32

If you compare the temperature from the different units in the initial recording at the 2 minute mark, you can see that it varied quite a bit (note the same FBC unit was both the lowest and highest temperature at this mark), which proved my testing imperfect. I concluded that the time it took to seal the bag and close the cozy would have a big effect on this, and that the end temperature didn't necessarily reflect the performance of the cozy. What does tell the story is how much the temperature dropped in each situation between minutes 2 and 10. Before the testing, my thoughts were that the FBC Minimalist and the Trail Designs models would be very close in performance, and my SUL cozy would trail behind but still might be worth while. I was shocked that the FBC Minimalist didn't do much better than my SUL, and at how well the Trail Designs unit held the temperature, especially as compared to the other units. I was further surprised that using no cozy at all didn't do much worse than the two bottom performers. 

CELEBRATE YOUR FAILURES!!!
While my SUL cozy was a nice try, it really didn't do much to hold the heat in. I found that putting the meal inside the pot and closing the lid did about the same as the 1.15oz cozy I have been carrying.  My conclusion is that for very mild temperatures, not bringing a cozy is fine, but the amazing little back country oven pictured here will probably find its way into my pack most of the time. Without the plastic cup it comes with, it weights only 0.7oz and folds up nice and flat. My failure in a MYOG project ended up being a success in saving weight while improving performance!