Hot tools are one of the beauty world’s great paradoxes. They make hair look smoother, shinier, and healthier in the moment, but if used incorrectly, they can cause breakage, split ends, and long-lasting damage.That doesn’t mean you should ditch your flat iron. You just need to know how to use it correctly to keep your hair healthy in the long run. And the big secret is knowing how hot your straightener or curling iron should be, so you can get all of the benefits from it and cause as little damage as possible.