Sparklers on a naked body can be a lot of fun, although there is a slight danger of minor burns. If you didn't use up your supplies over the holiday, or find them on sale now, give that some thought!
They burn at about 1.110 to 2,000 degrees Fahrenheit. Not wise to use anything that hot on naked skin. I have a small permanent brand on my finger from a burn I got from a sparkler when I was eight.The scare is still there 30 years later. Does that seem like a minor burn? If you want temperature play stick with melted wax and ice. Unless of course you want a reminder of the session 30 years later.
Sorry to hear about your permanent burn. I've played with fireworks a lot as a kid -- I come from a proud family of pyromaniacs who are very, very lucky to have all of their fingers intact -- and have no scars to show from it. Just like with wax play, allow some distance between yourself and your sub/bottom if you do this. But you are right, wax and ice is the safer route to go for temperature play.
A friend of mine told me about a scene she did with a Military man last year for the 4th of July. She got a ton of American flag themed decor to use... that's patriotism!