I’ve covered this issue before but I get enough questions about it to merit another post. I know there are scientific explanations as to why condensation occurs more on some days than others, but I can’t remember them. However, excessive condensation is a problem for solar cooks. It makes it harder for the cooking chamber to maintain high temperatures, lengthening, or in extreme cases halting the cooking process. Luckily it’s a problem that’s easy to fix. At least one of the following solutions should solve any condensation issue.
The first solution, which is the easiest and therefore my favorite, is to simply unlatch the glass door. Turn the latches so they’re not holding the glass down as in the picture below. Make sure the door is not resting on the latches. The condensation will be able to escape and the door will still be closed. It works like a charm here in Arizona where the sun quality is extremely good. Watch your Sun Oven carefully the first few times you try this fix. If it causes the temperature inside the cooking chamber to go down, try the next solution.
The second solution is to place an object, in the picture I used a wooden BBQ skewer cut in two, between the gasket and the glass door. Close the door and secure the latches and you normally would. This will allow the excess moisture to escape, although not as quickly as the above method, without any heat loss. I rarely have to use this method, in fact I don’t even have a designated object to use. In climates less favorable to solar cooking it is probably the way to go. Should I ever move to one of these climates I’d keep something handy with my other solar cooking accessories.
And finely, the third solution, which can be used in conjunction with either of the above two, is to place a tea-towel or a cloth napkin under the lid of the pot. I came up with this trick more to absorb excess moisture when preparing recipes like Bolognese sauce, which otherwise came out too watery, but I noticed that it also kept condensation at bay. You can use any color tea-towel, but as always with solar cooking, dark colors work better.