The Boil Cure Potion is a simple healing potion designed to cure boils. While the final color of a correctly brewed potion is not described in the novels, the brewing process involves several key ingredients and produces thick green smoke and loud hissing sounds. Known ingredients include:
The brewing process requires careful attention to the sequence of steps. An improperly brewed batch can be identified by acrid, green smoke and may result in the melting of a pewter cauldron.
The primary and intended magical property of the Boil Cure Potion is to effectively and quickly cure boils on the skin. It is considered one of the simplest and most basic potions in the curriculum. The brewing procedure is critical to its success. According to the instructions in Magical Drafts and Potions, the porcupine quills must be added after the cauldron has been taken off the fire. Adding them while the potion is still being heated will cause a dangerous chemical reaction, producing clouds of acidic green smoke and melting the cauldron. Furthermore, a failed Boil Cure Potion can have the opposite of its intended effect, causing the brewer to break out in painful red boils upon contact, as demonstrated by Neville Longbottom.
The Boil Cure Potion is most notable for being the first potion assigned to Harry Potter's class during their first Potions lesson with Professor Snape. This event served as a crucial introduction to the subject and to Snape's teaching style. During this lesson, Professor Snape introduced the potion as a simple brew, yet the class proved challenging for many students. Neville Longbottom famously brewed his potion incorrectly by adding the porcupine quills too early. His cauldron melted, and the spilled potion covered his legs, causing painful boils to erupt instantly. Hermione Granger, having successfully brewed her own potion, correctly identified Neville's mistake. Professor Snape blamed Harry Potter for the incident, accusing him of not stopping Neville, and sent Neville to the Hospital Wing. This class established the difficult and often unfair dynamic between Snape and Harry that would persist throughout their time at Hogwarts.
The Boil Cure Potion's primary role in the narrative is to establish key character traits and relationships early in the series.