Where did Hogwarts store all the cauldrons?

Question

We know that the cauldrons at Hogwarts are not communal but that each student buys their own one.

OTHER EQUIPMENT
1 wand
1 cauldron (pewter, standard size 2)
1 set glass or crystal phials
1 telescope
1 set brass scales
_{(Philosopher's Stone, Chapter 5, Diagon Alley).}

But no mention is ever made of the students lugging their heavy cauldrons around the castle on their way to Potions classes. The same is true of the phials, the scales and (for Astronomy) the telescopes.

Potions is a mandatory class for all students for the first five years, and each year-group is taught in two classes. Alongside the two N.E.W.T. classes, that means that there are twelve Potions classes in total, each using different cauldrons and Potions equipment with very little time for transition.

How is this managed practically without students having to carry their cauldrons around in person? Was there some storage area in the dungeons where they were all kept? How were the correct cauldrons brought into the classroom at the correct time for the start of each lesson? I know that there are house elves at Hogwarts who sometimes transport possessions about, but I'm not aware that they are mentioned in such a capacity.

Where were the cauldrons stored and how were they transported?

(Hat tip to Janus Bahs Jacquet for asking the same question in a comment two-and-a-bit years ago).

Answer 1

This may answer some parts of your question.

All cauldrons are enchanted to make them lighter to carry, as they are most commonly made of pewter or iron. Modern inventions include the self-stirring and collapsible varieties of cauldron, and pots of precious metal are also available for the specialist, or the show-off.

_{(Pottermore, "Cauldrons")}

Answer 2

Possibly their cauldrons were stored in the Potions classroom.

It seems like, at least some of the time, students leave their cauldron in the Potions classroom. They take them back after each school year, since Harry has to pack his cauldron to go to Hogwarts each year, but it seems like once the students are in Hogwarts, they at least sometimes (if not all the time) leave their cauldron in the classroom. This may be so they don’t have to carry it around every day, and may also be so that that they can brew potions that take more than one day to brew. If they’re able to leave the cauldrons in the classroom, then they can leave a still-brewing potion in their cauldrons, and go back to it the next time they go to class.

There’s rarely any detailed description of anyone packing up to leave class, but we do see a few clear examples of students leaving their cauldron in Potions class.

When Hermione was in the hospital wing because she’d been Petrified, her cauldron was still on her desk in the classroom.

“Snape swept past Harry, making no comment about Hermione’s empty seat and cauldron.”
_{^{- Harry Potter and the Chamber of Secrets, Chapter 15 (Aragog)}}

In addition, we see Harry pack up his things after Potions class after spilling on purpose so he could linger around and spy on Snape. He packed up and took his books and ingredients, but not his cauldron.

“‘This,’ said Karkaroff, and Harry, peering around the edge of his cauldron, saw Karkaroff pull up the left-hand sleeve of his robe, and show Snape something on his inner forearm.

‘Well?’ said Karkaroff, still making every effort not to move his lips.

‘Do you see? It’s never been this clear, never since –’

‘Put it away!’ snarled Snape, his black eyes sweeping the classroom.

‘But you must have noticed –’ Karkaroff began in an agitated voice. ‘We can talk later, Karkaroff!’ spat Snape. ‘Potter! What are you doing?’

‘Clearing up my armadillo bile, Professor,’ said Harry innocently, straightening up and showing Snape the sodden rag he was holding. Karkaroff turned on his heel and strode out of the dungeon. He looked both worried and angry.

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)}}

In that case, Harry knew Snape would be in a bad mood, so it’s unlikely he’d leave his cauldron if he knew he was supposed to take it, otherwise he’d find himself in bigger trouble for cluttering up the classroom.

Answer 3

The cauldrons are transported by magic

Harry looked down at his empty gold plate. He had only just realized how hungry he was. The pumpkin pasties seemed ages ago.....Harry’s mouth fell open. The dishes in front of him were now piled with food. He had never seen so many things he liked to eat on one table: roast beef, roast chicken, pork chops and lamb chops, sausages, bacon and steak, boiled potatoes, roast potatoes, fries, Yorkshire pudding, peas, carrots, gravy, ketchup, and, for some strange reason, peppermint humbugs.

-Harry Potter and the Philosopher's Stone

Here, we see that the food from the kitchens gets transported to the Great Hall, during the feast. The same principle could be applied to the cauldrons as well. They could be transported magically from wherever they're stored. Students need not carry the cauldrons around all the time. They just need to buy them and bring them to Hogwarts once.

Professor Dumbledore paused, about to leave the hall, and said, “Oh, yes, you’ll be needing…” One casual wave of his wand and the long tables flew to the edges of the hall and stood themselves against the walls; another wave, and the floor was covered with hundreds of squashy purple sleeping bags.

Here's another example, although it could be a conjuration instead of a summoning. Perhaps Professor Snape has found a way to separate the cauldron's belonging to each year's students.

OTHER EQUIPMENT

• 1 wand
• 1 cauldron (pewter, standard size 2)
• 1 set of glass or crystal phials
• 1 telescope set
• 1 brass scales

-Harry Potter and the Philosopher's Stone

Since all students belonging to the same class year use cauldrons of the same type, it may not be necessary to identify and transport each cauldron exactly to the one who bought it. So, If it's a first year potions class, just summon any pewter cauldron size 2, from storage.

However, I have no idea, where exactly, the cauldrons are being stored.

Answer 4

Pure speculation. If a student takes only one potions class per semester, he could store his cauldron in the classroom storage closets. I guess there may be one cauldron storage closet for each separate potions class in the classroom and the cauldrons could be inscribed with the students's names or have name tags tied to them. But if students takes two or more potions classes per semester they could open a hatch in the classroom and put their cauldrons on a conveyor belt in a secret passage leading to to the next potions classroom with magic or house elves moving the belt