A Croftybomb is a bottle with a mixture of sodium hydroxide (in this case the plunger) and aluminium. This mixture creates heat and hydrogen. When the pressure inside the bottle reaches a certain amount, the bottle will explode. Take the bottle filled with water. Put some pieces of aluminium in it (experiment with the amount, don't start with too much). Now the harder part: take the plunger and add it to the bottle, put on the lid, shake it a few times and throw it away. Be fast, 'cause the bottle gets warm after about 1 sec and could explode within 3-4 seconds if you add too much. Just start of with a small amount of aluminium and plunger, experiment but be careful! Note: Contact with the smoke after the bomb has exploded could cause burns, so watch out!
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