Last Saturday I found myself lounging at a barbeque in Merced, drinking soda and playing with my nieces and nephews in a sunny backyard.  As I stared at the bag of discarded aluminum cans, I decided this would be the perfect day to try a new fire-making trick: Making fire from a Coke can and toothpaste.

The convex bottom of a coke can is a nice little parabola. If that aluminum is shiny enough, and oriented towards the sun,  it should be able to focus the incoming light energy into a tiny spot, exactly like focusing sunlight with a magnifying glass.

It should work, as long as I could get the aluminum shiny enough, and find some appropriately flammable tinder.

So, I began polishing the aluminum.

Much like the plan for starting a fire with two sticks, the idea behind starting a fire with a coke can and toothpaste is that one day you might find yourself stranded somewhere with limited resources. Coke cans are pretty common, and I can definitely imagine a scenario where your cruise ship is sunk in the Aegean Sea and the only materials you have were in the styrofoam cooler you dragged ashore.

The toothpaste is a gentle abrasive. Sand is also an abrasive, but sand would probably leave bigger scratches than the ones it was smoothing. I've also heard of fire-making Coke cans being polished with chocolate.

I squeezed a little toothpaste onto a cloth and began slowly smearing it around the bottom of the can. 

 Within just a few  minutes, I could see that the tiny scratches in the aluminum were disappearing, and the can was becoming a crisp  reflector.

After 20 minutes, I went outside and tried to start a fire.

This was going to take some finesse, so I decided to mount the can in a fixed position. I propped the can up on it's tab, pointing it directly at the sun. This was easy, I just moved the can around until it had the smallest possible shadow.

I put my finger into where I thought the light should convene. It was warm, but not exactly a crisp pinpoint of light.

Next, I found a twig, about the size of a matchstick, and started poking around for the focal point of the sunlight.

Here is a photo of Richard giving it a try. He was the first one to get smoke.

It wasn't easy. The focal point was tiny, and it was hard to find. The twig needed to be in the exactly right position for the hot dot to be on its surface, but after it crispified that one speck of the twig, there wasn't any fuel left there, so I had to move the twig to focus the light on a new, unburned spot.

I was getting some little curls of smoke, but fire seemed really far away.

It felt a bit like I was trying to make toast with a laser.

After a while, toying with the can and consulting the other pyromaniacs,  I decided to try some more polishing. I sat for another 30 minutes, rubbing toothpaste into the bottom of the coke can. 

Coke and toothpaste are usually mortal enemies, so it was nice to see them both working together like this.