This prank will aggravate them four-fold. Firstly, their shampoo bottle will appear blocked, causing them to squeeze it harder. Secondly, it will explode 'shampoo' (actually cornflour and water) all over them. Thirdly, if you carry it off well, they will think they wasted all their shampoo. Especially annoying since shampoo is so expensive! Lastly, if they don't notice it's not quite its normal consistency, they might rub it in their hair!
- sharp knife
- glue gun
- mixing bowl
- empty shampoo/conditioner bottle (must be opaque)
- food colouring (optional)
Step 1: Which Bottle to Choose?
Once you've picked your bottle, rinse out the bottle, being careful not to wash off the dried shampoo from underneath the cap. Making the bottle too clean will give the game away!
Step 2: Modifying the Bottle
To get the top to pop off when squeezed, this ring of plastic needs to be filed down slighly. I found the best way was to carve little bits of the plastic off with my scalpel. I took a little bit off at a time, checking after each time how much pressure was needed to pop the cap off. When I got it so that it would pop off with a little pressure but stay on when lifted I called it quits.
Step 3: Blocking the Cap
To do this when the cap is open the hole needs to be plugged. I found the best thing for this is a glue gun.
Carefully work a layer around the hole then mound it up over it. Don't plop it in the hole from the start or it'll be visible poking through the hole when your victim opens the shampoo bottle. If the glue is visible from the outside when you've finished, smear some shampoo over it so it looks like it's just dried in the hole.
Step 4: Replacing the Shampoo
Measure out about 250ml water (the volume of the bottle in this case) and add about 50ml to the cornflour, stirring it until it's a smooth paste.
Add the rest of the water to make a fairly runny white liquid. If your cornflour/water mix is too thick it won't explode out. Mine was the consistency of single cream (if you didn't want to do this mixing, cream would probably be a good substitute as it's cheaper than shampoo). If the shampoo you're replacing was slightly coloured add a tiny tiny drop of food colouring to give it the right tint.
Pour the mixture through the funnel into the bottle and whack the cap on.
Now you are ready! Switch it for the real deal and wait within earshot to hear their laughter/scream/anger.