We've just discovered what those extra red-tipped bulbs that come with Christmas lights are for...

The festive period is well and truly upon us and that means festooning our homes with beautiful lighting, both inside and out. A front porch decked with sparkling lights really is one of the most magical sights at Christmas time, but your set might have an even more special feature that you didn't know existed. 

Ever noticed that red-tipped bulb that comes with your string lights when decorating your Christmas tree? It might look like a strange imposter but it has a very useful purpose, and people on TikTok are finally finding out what it's for. 

It's safe to say, we're all pretty amazed. The clever little hack takes less than a minute and promises far more magical Christmas lighting, and you might want to know about it before you buy new lights. Here, we take a look at how it's done. 

What are red-tipped Christmas light bulbs for?

It's a core memory we all seem to share - rummaging in your decorations to find a packet with a random red-tipped lightbulb alongside a spare one. Truthfully, I never knew what it was for when Christmas decorating and had always assumed it was mistakenly put in there. Well, it actually serves a very important purpose that I'll now be using every year: it's known as a flasher bulb, and it can make your string lights twinkle!

@viznelly

♬ It's Beginning To Look A Lot Like Christmas - Bing Crosby

How do flasher bulbs work?

Whether it's the lights on your Christmas tree or your outdoor Christmas decorations, there's no denying that a bit of sparkle brings the magic at this time of year. These strange little red bulbs offer just that, but how do they work?

Essentially, all it involves is swapping out one of the original light bulbs with a red-tipped one somewhere on your incandescent string lights (bear in mind, this trick won't work with LEDs). From that bulb onwards, the lights in the string after that bulb will blink. Depending on where you switch out the bulb, you can make the whole string or just half of them blink. 

It might look like magic, but there's actually a technical explanation for this sorcery. These red bulbs contain an extra strip of metal called a bi-metallic strip which bends as the filament in the bulb heats up from the light current, causing the lights to go out. As the strip cools, it straightens out, reconnecting the circuit and thus switching on the lights. 

This is the simplest and easiest way to transform your string lights into a magical twinkling set without needing to set extra functions or buy specially designed flashing ones - and boy, did I wish I'd known it sooner. Paired with the Christmas tree trunk lighting hack, I think it's safe to say that this year I'll have the most magical tree going...