my first success with the fresnel lens was camping this summer - and it was very easy when I found the secret.

punky wood. I scraped some out of the south side of a standing rotting snag. got a couple handfulls. Rubbed the material in the hands to break it up. flash the lens and a small "coal" is all you need. the beauty of this material is that when you blow on the coal, it expands rather than extinguishes. Just mix in a few small twigs or birch strips and blow blow blow. soon smoke (lots) then flame. It was so simple and the key was the punky wood!

regarding the product in the post. if you are in an area like me (NH) where the sun is not so strong in the winter, you need to keep the light focused for some time to get substantial heat. this product would be much easier to "rig" in a fixed position to leave and tend to other tasks while the sun remains focused.