Instructables
Picture of Cardboard and Water Magic Trick
Amaze your friends with this easy magic trick.
 
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Step 1: Materials

Picture of Materials
-pocket knife
-cardboard
-water
-cup (in my opinion a clear glass works the best).
 

Step 2: Cardboard

Picture of Cardboard
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Cut the cardboard so it is a little bigger than the glass.

Step 3: Water

Picture of Water
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Fill the glass about 1/4 of the way full. Then place the cardboard on the top of the glass.

Step 4: Done!

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To start out put your hand on the cardboard and slowly tilt the glass upside down so that all of the water is sitting on the cardboard. Then slowly and carefully remove your hand off the cardboard. the cardboard should stay on the glass! Any sudden movements will cause the cardboard's seal  to fail resulting in a mess full of water.
Jerryfrye1 year ago
This is also useful if you get bad service at a restaurant. Place your tip in a water glass. Put the cardboard on and turn it upside down. Then you can set that on your table and slide the cardboard out. That leaves an upside down glass of water that can't be moved without making a mess. Not that I would ever do that. :-)
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nerd7473 Jerryfrye11 months ago
LOL that is funny!
thank you for the idea :D
Mean... but priceless! ;-D
sisar1 year ago
nasty cut you got there buddy!
Dude be careful with knife in the next instructable. I could see some marks on your thumb in this instructable. take care.
rjprod1 year ago
I sure it was easier to do the trick then to invert the camera...take the picture...then have to reverse all the background images!!
joearrieta1 year ago
Dude careful with that knife or you'll hurt yourself, oh wait...never mind.
I haven't seen the one where the water stays in the glass, but if you can't reproduce it, it may just be an upside down camera ;)
HelenaTroy1 year ago
reminds me of when I used to work in a pub, of a tirck they'd pull now and hten. Put a beer mat on top of the glass, invert it, put the plass down on the bar, then carefully slide out the mat - the beer stays in the inverted glass, with no way to rescue it - can't get anything under the glas without breaking the seal and letting the contents loose..
natsterrr1 year ago
I've seen a youtube clip where they remove the cardboard and the vacuum + water tension keeps the water in the glass! I haven't managed to succeed with that one yet, I'm not sure whether there is a secret trick to it or not...
It's not magic it's physics! You should search and explain why this happens I don't know how to explain it in english but It's something about atmospherical presure.
Magic is just stuff science has not made boring yet.

"Yesterday's magic often becomes today's technology.
It is then taken for granted as the magic seeps away."

"Any sufficiently advanced technology is indistinguishable from magic."
― Arthur C. Clarke

Yes, it is magic. And, yes, it may be physics - but I don't believe in physics, so I'm not sure.
jcvillar1 year ago
I'm guessing the weight of the water is causing the cardboard to flex outward, thereby causing the pressure drop.
qewt1 year ago
neat!
Uses a simple yet very breakable vaccum in the cup