"Now this isn't like other spells. You need to keep moving your wand in a circle to build up power."
—A charms professor teaching a student[src]

One can increase the power of a spell by waving their wand in circles before casting a spell. The spell, once its power has been increased, will change colour from its ordinary colour to a different colour. If one attempts to charge a spell more than the spell should be charged, it will backfire in mid-air and cause minor damage to them.

Behind the scenes