- "Second-year Hogwarts students brew Swelling Solution in Potions class. This potion causes things to grow and expand. Its effects can be reversed with a Deflating Draught."
- — Description[src]
The Swelling Solution was a potion which caused whatever it touched to swell in size. Its three ingredients were bat spleens, dried nettles, and puffer-fish eyes. Fermentation was needed before it could be considered a proper stable potion.
The trio decided to steal some ingredients for the Polyjuice Potion from Professor Snape's private stores in their second year the day the class tried to make this potion. Harry Potter set off one of his fireworks as a diversion for Hermione Granger to get the necessary ingredients; whether intentionally or accidentally, the firework landed in Gregory Goyle's cauldron, causing the solution to explode across the class, most notably affecting Draco Malfoy, who got it in the face and endured his nose swelling to the size of a melon, and Goyle himself, whose eyes expanded to the size of dinner plates; other afflictions included arms like clubs and gigantic puffed-up lips which rendered speech impossible. Those splashed had to go to Snape for a Deflating Draught.
- Add 2 scoops of dried nettles to the mortar
- Add 3 puffer-fish eyes to the mortar
- Crush into a medium-fine powder
- Add 2 measures of the crushed mix to your cauldron
- Add two tablespoons of water to the powder in the cauldron and mix them together
- Heat on a medium temperature for twenty minutes
- Add some more water to the cauldron and stir the mixture carefully
- Wave your wand
- Leave to brew and return in 60 minutes (depends on the type of cauldron used)
- Add 1 bat spleen to the cauldron
- Stir 4 times, anti-clockwise
- Heat to low for 30 seconds
- Wave your wand to complete the potion
Behind the scenes
- Given that every potion's brewing process can only be completed by casting a spell, and that it can vary for each potion, the most likely spell used to complete this potion is the Engorgement Charm.
- Harry Potter and the Chamber of Secrets (First appearance)
- Harry Potter Trading Card Game
- Fantastic Beasts: Cases from the Wizarding World (Mentioned only)
- Harry Potter: Hogwarts Mystery
- Harry Potter: Magic Awakened