We can probably easily tell at a glance what were drinking, especially if the cup or mug were drinking from is clear as glass. But what if that glass had a special trick that would literally spell out its contents? Sounds like a Harry Potter prop, definitely, and were probably decades away from such a smart piece of drinkware that can clearly label what you pour inside it. But as some would say, fake it till you make it, and these simple-looking clear glasses and mugs definitely try.At first glance, they seem like normal transparent glasses, but once you pour milk or coffee, their magic starts to appear. It almost feels like theyre magically telling you which drink theyre holding, but once you realize the trick, youre bound to smile at the silly yet effective mind games that these text-changing glasses play.Designer: TOALIt definitely sounds like a helpful feature to have a cup that tells you in bold letters whats inside. Of course, if the cup is transparent anyway, it becomes more of a fun detail that adds a little flavor to your favorite drink. Figuratively, of course. These glasses and mugs have Japanese words for coffee and milk written on them, and only one or the other is visible, depending on which one is actually poured inside.Its really a simple visual trick that takes advantage of the natural colors of these two drinks. Coffee is normally black or dark brown, depending on the brew, so the dark Milk text vanishes when the glass holds coffee. The opposite is true for white milk, making the white Coffee label invisible. And when you mix the two together? You see both words appear, indicating a mixture of both liquids.Of course, the illusion breaks down if you pour in any other color of liquid or if the glasss contents go below these words. Its not a trick that will completely amaze your guests, but its good enough to have a laugh or draw a smile to anyone who figures it out. Plus, its always fun to watch one or the other word disappear, only to reappear when you mix coffee and milk.As for the drinkware itself, its pretty standard clear glass, though there are different designs that use heat-resistant glass. That sadly means you cant use the same vessel for both hot and cold drinks, though having a collection of these doesnt seem to be a drawback. The text is printed using silk printing, which the brand says is more durable than either UV or pad printing but could still peel off if a strong impact is applied to the printed area.The post Coffee and milk glasses have a simple but fun way to tell which drink it holds first appeared on Yanko Design.