I got it to work, but I feel like I cheated.

First, I polished the bottom of a Mountain Dew can using my thumb and a lot of toothpaste. Took about 20-25 minutes. Shiny, formed a reflected image, but fuzzy. A little Flitz fixed that. :-)

I've never started a fire with anything other than matches, so I was guessing at tinder and technique. I used cotton gun cleaning pads smeared with a little charcoal from the grill. The charcoal made the cotton dark enough to really absorb the sunlight well.

After just a few seconds, the cotton smokes nicely. I never could get it to ignite, though. Tried different ways of packing it, holding it, fraying it. Same result.

I finally got a fire by getting the tinder smoking nicely, then wrapping it in some dry grass (easy to find in Florida right now) and blowing, gently, for a minute or so. smoke, smoke, Smoke, SMOKE, Flame! Yay!

What would make a better tinder? And if you're going to do this "for real", what could be done to the standard cotton ball / vaseline tinder to make it more appropriate for solar powered lighters like this? I'm also curious what natural tinders work with this technique. I tried the dried grass by itself, but it would only smoke a little bit, going out instantly after I took it away from the can.

(I say I cheated because of the Flitz and charcoal. But then, toothpaste isn't in my PSK either, so...)

Re: focus

For a pop can stove, one could mark the focal length on the side of the can for furture reference.

A piece of wire could be fashioned, bent into an "L" shape and held in place with either a ranger band or duct tape. That would save your grip as well as keep the tinder in the right spot. Perhaps a thin twig could hold the tinder in a pinch too. If you choose a thin, green branch and bend but don't break it all the way through, into a 90 degree angle. Use a tab of duct tap at the bend as a brace to hold the angle as the twigs tendancey will be to bend back.

Just some thoughts

Congrats, you didn't cheat if it worked <img src="images/graemlins/wink.gif" alt="" /> I've tried the typical PSK tinders like ranger band, tinder Quick ect. without much luck. you want anything that will take and grow a coal, char, tinder fungus ect. then the coal goes into a nest of fine tinder and you blow it to flame. That's the way almost all the primitive methods work.
By the way i consider this a secondary/bushcraft/ match extending tech., but it does have its uses, look at all the burning lens in PSK's and oldtime tinder boxes.
If you liked the coke can you should like the Saran Wrap method Walter has on his site now.

Mike

Ya think that you could take the kit-kat wrapper and simply press it on to the bottom of a can - shiny side out? would that save on polishing time? just a thought. . .