How can students learn making potions when some of them take months to complete? Sleeping Draught takes 70 minutes to brew, and since the Draught of Living Death is a lot more complicated than previous ones it is safe to say it takes longer to brew, yet Slughorn expects students to brew it during one class (I know Harry used shortcuts from the HBP book, but Slughorn did not know that). I understand simple potions are easy and some of them take a lot less time to brew. Even those that take up to a week I understand, since they can brew them until next class and finish then.

So my question is how do students learn advanced potions if it takes them so long to brew?

  • 3
    They learn over time? Coursework style?
    – user46509
    Jan 28, 2016 at 19:20
  • 3
    Hi, I'm a chemist. Frequently projects may require classes to run a reaction over the course of several weeks or even months as the steps are done slowly but also without sufficient time to do in one sitting. For example, synthesis of aspirin typically includes drying for a week to reduce the amount of moisture present and affecting your calculated yield. Does it need a week? No, but it also can not be completed during the class period for that week
    – Broklynite
    Feb 14, 2017 at 23:10
  • So you are saying that they start bunch of potions and see them trough the year? Feb 15, 2017 at 22:35

3 Answers 3


First years are required to take seven courses, and Second years are required to take up an additional two. In Hogwarts, classes vary in length (canonical - quote later), and some classes are in a row designated as "double". Since there are seven classes in one year - using common sense, class lessons are stretched over this period as well, know an "units".

Due to this, it can be understood that potions in Potions class are brewed in extended periods of time - also in divisions known as "units" in the Muggle world.

  • So if I understand you correctly they brew multiple potions at same time? Jan 28, 2016 at 19:37
  • @VanjaVasiljevic I just know that in the Muggle world classes are divided into units, and they do not overlap each other. They go unit by unit. As for the wizarding world, I'd only assume so.
    – Jake
    Jan 28, 2016 at 19:40
  • OK, Ill accept it, Al tho it doesn't seam practical to me but :D Jan 28, 2016 at 19:49
  • 3
    @VanjaVasiljevic If you're growing a seedling for a biology class, you don't do nothing else until the seedlings grow. Case in point: Herbology did more than just wait for the Mandrake Root to grow in Chamber of Secrets. So, if you're waiting for one potion to brew, you don't stop all other work.
    – user31178
    Jan 28, 2016 at 20:13
  • 1
    I think Jake has a satisfactory answer, but I'll add that there are many things IRL that students learn that can't take place in an ordinary time span. Just look at 30min cooking shows. They show you how to start it, but then have one that's already chilled, rested, marinade, etc... So it seems to me that's it's likely in potions that they would learn how to work with part of a potion and if they needed to work a long running potion they'd have ones that the professor prepared ahead of time.
    – Dalton
    Jan 29, 2016 at 19:51

They leave their cauldrons in class, so they could work over time.

Students at Hogwarts seem to leave their cauldrons in the classroom most of the time. For potions that take a long time to brew, they could leave it in their cauldrons in the classroom, and work on it through the course of over whatever amount of time it needs to brew. It seems like we witness this happening during at least one class. During his class, Harry added ingredients into his cauldron.

“He tipped his ginger roots into the cauldron too, and wondered whether he ought to take a leaf out of Moody’s book and start drinking only from a private hip-flask.”
- Harry Potter and the Goblet of Fire, Chapter 27 (Padfoot Returns)

He doesn’t empty the cauldron after that, and packed up to leave without having emptied the ingredients we know he just put in. Also, he’s aware Snape is in a bad mood, so he wouldn’t have cleaned up halfway and given Snape something to be angry at him about.

“Not wanting to remain alone with an exceptionally angry Snape, Harry threw his books and ingredients back into his bag, and left at top speed to tell Ron and Hermione what he had just witnessed.”
- Harry Potter and the Goblet of Fire, Chapter 27 (Padfoot Returns)

It seems like they left in the middle of brewing a potion, leaving some ingredients in the cauldron, and presumably they’d return to it as they needed, until it was done. As Valorum points out in the comments, there are self-stirring cauldrons for potions that require constant stirring.

“The sun shone brightly on a stack of cauldrons outside the nearest shop. Cauldrons – All Sizes – Copper, Brass, Pewter, Silver – Self-Stirring – Collapsible said a sign hanging over them.”
- Harry Potter and the Philosopher's Stone, Chapter 5 (Diagon Alley)

It would then be easy to start a potion brewing and revisit it in subsequent classes until it’s done.


Intermediate results are informative.

While a high-quality final product is the ultimate goal of any potion recipe, students can gain longstanding skills by learning about methods and indications throughout the creation process.

For example, the procedure to create the Draught of Peace, although brief enough to complete during a single lesson, demonstrates that intermediate results provide useful quality-control information to the potion-maker:

'A light silver vapour should now be rising from your potion,' called Snape, with ten minutes left to go.

Harry, who was sweating profusely, looked desperately around the dungeon. His own cauldron was issuing copious amounts of dark grey steam; Ron's was spitting green sparks. Seamus was feverishly prodding the flames at the base of his cauldron with the tip of his wand, as they seemed to be going out. The surface of Hermione's potion, however, was a shimmering mist of silver vapour, and as Snape swept by he looked down his hooked nose at it without comment, which meant he could find nothing to criticise. At Harry's cauldron, however, Snape stopped, and looked down at it with a horrible smirk on his face.


'Did you do everything on the third line, Potter?'

'No,' said Harry very quietly.

'I beg your pardon?'

'No,' said Harry, more loudly. 'I forgot the hellebore.'

'I know you did, Potter, which means that this mess is utterly worthless.'

Harry Potter and the Order of the Phoenix, Chapter 12: "Professor Umbridge"

The Draught of Living Death offers similar feedback:

Harry stirred counter-clockwise, held his breath, and stirred once clockwise. The effect was immediate. The potion turned palest pink.

'How are you doing that?' demanded Hermione, who was red-faced and whose hair was growing bushier and bushier in the fumes from her cauldron; her potion was still resolutely purple.

'Add a clockwise stir –'

'No, no, the book says counter-clockwise!' she snapped.


Slughorn moved slowly between the tables, peering into cauldrons. He made no comment, but occasionally gave the potions a stir, or a sniff. At last he reached the table where Harry, Ron, Hermione and Ernie were sitting. He smiled ruefully at the tarlike substance in Ron’s cauldron. He passed over Ernie's navy concoction. Hermione's potion he gave an approving nod. Then he saw Harry's, and a look of incredulous delight spread over his face.

'The clear winner!' he cried to the dungeon.

Harry Potter and the Half-Blood Prince, Chapter 9: "The Half-Blood Prince"

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.