So I normally carry cottonballs covered in vaseline as a firestarter. Pretty lightweight, does the job. They're also messy, and require their own plastic bag, etc.
I also carry Chapstick with an SPF 30, because sometimes when my lips get too much sun, I get a cold sore. On top of that, super chapped lips from lots of cold/wind/wet just aren't all that fun.
It occurred to me today that I might be able to combine the two, since the main ingredient in Chapstick is petroleum jelly. I decided it was an interesting enough idea to test it out, so I gave it a try.
I took two cottonballs, and then took a small gob of chapstick and worked it into one of them. Using my woodstove, with the door open (figured it was a decent enough, wind-free control environment), I lit both of them and timed 'em.
Cottonball without Chapstick: 40 seconds burn time, small amount of smoldering.
Cottonball WITH Chapstick: 2 minutes, 5 seconds burn time, smoldered long enough and hot enough afterward that I still could have used the embers to get a flame going.
Pretty awesome!
Two minutes should be enough to get most damp/wet tinder going. This should eliminate a small amount of weight from my kit between the vaseline and bag, although not enough to make much of a difference. The main thing is, it streamlines things.
Instead of keeping messy, vaseline-covered cottonballs in their own bag, I'll just store a few of them in the same small bag as my first aid and emergency supplies, making the cottonballs available for other applications. For instance, if I need a better bandaid than duct tape, I can use them to pack a small wound or sop up/control bleeding.
Anyway, not the biggest deal in the world, but I was excited that it worked so well, and it gives both my chapstick and cottonballs another use. Not bad!

