Imagine. You're in a dark, mysterious cave. The air is cold and clammy, and the dripping stone walls are covered in strange runes and symbols left by ancient civilisation. Or aliens, we have no idea. Are they curses? A treasure map? Some kind of shopping list? If only you'd brought your blacklight to help you decipher them!

Never mind - with just a few things from around the house, you can transform your mate's brother's younger cousin's old phone into a pretty decent blacklight! Let's find out how!

You Will Need:

• A phone with a torch
• Sticky tape - ideally Scotch Magic tape
• A blue marker pen
• A purple marker pen
• Scissors to cut the tape

And very importantly...ahem...

Permission from whoever owns the phone!

Step 1

Find the torch on the phone. It's usually next to the camera. Oooh, by the way - make sure you don't mess about with the camera part!

Step 2

Take a small square of tape. You can cut it with scissors, or just rip it apart with your teeth like some kind of wild animal. Now stick the tape over the torch.

Important! We recommend Scotch Tape for this because you can remove it once you're done, and it doesn't leave a sticky mess. Other tape might - you have been warned!

Step 3

Colour in the tape with your blue marker pen. Try not to get pen on the rest of the phone! It only needs to cover the torch. Ignore any hedgehogs that might be getting in the way.

Step 4

Now do steps 2 and 3 all over again! So cut another bit of tape and stick it over the first one, then colour it in blue again.

Step 5

Stick a third piece of sticky tape on top, and colour it in purple this time.

Step 6

You should now have 2 layers of blue tape, and one layer of purple tape covering the torch. Now switch your torch on! It should make an eerie blue glow. If it's not blue enough, you can just stick on more layers of purple or blue tape!

You can now use your DIY backlight to read hidden messages written in yellow highlighter - just look at these spooky runes!