This centuries-old classic trick is named for the Latin phrase "multum in parvo", meaning "much in little" or "a great amount in a small space".
And that is exactly the effect!
You start with a small glass of milk, and pour it into a larger glass.
Your audience would expect that you would only be able to fill half the larger glass- but NO!
As you pour, you fill the larger glass!
Next, you take that larger lgass, and pour the milk into an even larger glass.
Again the larger glass becomes full!
Of course, you go on to fill the next biggest glass as well!
You end up with a GIANT full glass of milk- all from that first small glass!
Where did the extra milk come from??
You can end the routine there, or you can really blow their minds.
Take the giant glass, and pour the milk into the next SMALLER one.
You'd think that there would be too much milk, and the milk would overflow.
The milk has shrunk, and now exactly fills the smaller glass.
Pour that glassful into the next smaller size.
Again no spillover, the amount of milk has again shrunk and only fills the smaller glass.
Finally, you end up with the original small glass full of milk.
Where did the all the extra milk go??
What a finale!
The glasses are a matched set of heavyweight clear plastic, with a clever design to make the set more deceptive to use.
This is not a closeup trick.
It is best to perform this trick at a distance from your audience, like from a stage.
The milk will show up well from a distance, and is easy to see.
Make sure to wash the glasses as soon as possible after use, or they will stain.
Use mild soap and warm water, and dry with a lint-free towel or cloth.
DO NOT USE abrasive cleanser or a scrub pad or you will scratch the plastic!