HARRY POTTER Cold Changing Large Glass - Hogwarts. Officially licensed merchandise. This Harry Potter glass is an absolute must-have for every fan of the world of witchcraft and wizardry. Room temperature, the front of the glass shows the Hogwarts Crest in black and white on the front and the Harry Potter logo in white on the back. When cold liquid is poured in, the Hogwarts Crest transforms to show its yellow borders and house colours. Once the drink is finished the glass returns to its original state as it warms back up to room temperature. A perfect gift choice for a true Harry Potter fan.