I love the flexibility of spiral ponytail fasteners like the Invisibobble for creating easy updos, but I can't stand the way my thick hair stretches them out after just one use. While they'll still do the job after they've stretched a bit (and they're hardly expensive to replace), these hair bands work best when they're new, in a tight coil that grips the hair without denting it the way elastic bands do.
Luckily, there is a simple beauty hack that'll take that stretched-out band back to its original form: simply pop it into a cup of boiling water. The Invisibobble will shrink back to its normal size in a matter of seconds. You may need to give it a helping hand on the final twist if it's particularly bent out of shape, but it really works.
Just take a look at how much better mine looks after its boiling bath. One word of warning: in my experience, this only works on the slimmer and more flexible bands. I've tried it on thicker, cheaper options bought from discount stores, and though they do shrink up a bit, the band won't regain its shape in quite the same way. So this is one instance where it's worth buying the original.