Ultraviolet Business Card Flashlight

Step 8 Have fun!

Now it's time to give your cards away ... although you might want to have a play yourself first!

If you didn't see some of the fun pictures in the Introduction to the instructable have another look now for ideas ... here are a few things to try:

• Look at foreign bank notes, passports, drivers licenses - even a 2nd class (UK) stamp has a hidden mark on it.  Tonic water fluoresces (only slightly), credit cards are great as well and usually have a couple of secret marks on.
• Draw on something with a highlighter pen (yellow and orange works best I think) and then look at it under the UV torch.  I like to draw a picture of a skeleton on the back of my hand with a yellow highlighter when I'm doing workshops - the kids love this.
• If you've got anything that glows in the dark, you'll be able to energise it with the torch (make it glow).  If you hold it really close (with the LED touching it, you will probably be able to 'draw' with light!
• Get yourself a UV pen to security mark your valuable at home or just to write messages in invisible ink.  If you do want to use this for secret messages, it works great on the back of one of the blank PVC cards.  Standard paper has whiteners added that make it hard to see the message - you might have more luck with brown paper.
• When it is really dark, go hunting in your bathroom to see how well it is being cleaned ... certain bodily fluids (like urine) fluoresce under UV light.
• One activity which is really fun is to see how well you wash your hands.  You can get a cream that you rub onto your hands before washing them (http://www.glitterbug.com).  Anything left afterwards (and there will probably be a surprising amount) will glow strongly.
• Some types of bacteria glow under UV light, although you will probably need to culture them properly in a petri dish as small quantities on surfaces, etc will not fluoresce.
• Theoretically you could also find many types of scorpions with this light, as they fluoresce as well!

Have fun!