I thought of making a Solar Dryer for my tomatoes. Reading suggests that electricity for store-bought ones runs up the actual cost quickly. In a few hours of reading up on the subject, other uses came to mind.

Making a high quality heating box, it might be possible to put it to three uses. Dryer, cooker, and window furnace in the winter.

One DIY type I saw on TV was a model using sand in soda cans. The maker said his temperature neared 400F.

I read all the labels at the big box store. Looking for a service range of 0-400 degrees F, could not find anything. Most tubes of caulk said nothing, one said it was suitable for -60to 250, and one said up to 150. Even the silicone stuff at $6.50 a tube did not appear to be suitable.

Any suggestions as to which type of caulk or other stuff to use?