Maybe a more interesting question is if canon ever has any potion go bad after being brewed? None come to mind right now.

 

It can be inferred to some extent. For instance, there was no supply of mandrake potions in Britain in COS, they had to be brewed from a fresh batch of mandrakes that spring.

Even if the potion was not commonly used, with an infinite shelf life you'd expect some sort of stockpile.

 

Aha! Another example. Snape has to brew the wolfsbane potion every month. Given it is only for Lupin, we can assume the potion can only be brewed in a small quantity, for whatever reason; or more likely, it is only "good" within a period.

To tie into cheddartrek's desire for useful!Astronomy, it would be reasonable to assume that wolfsbane's potency only lasts until the next full moon after it is brewed.

 

I feel like they probably don't due to Slughorn not warning Harry when giving Harry his prize of Felix Felicis. One of the most complicated potions has a shelf life of at least 9 months... Or you'd think there are work arounds with stasis charms or something of a similar ilk. Imagine saving liquid luck for a specific occasion only to find it's expired...

 

For most potions, I'm content to assume that they do go off after a while, and it's just not covered in the text because it's just not relevant (and in-universe, why would Harry care how long, say, a Draught of Peace lasts?). Polyjuice leapt out at me during my reread of DH though as being very plot convenient, and @Hush's point about Felix Felicis is a good one too.

I do like the Astronomy explanation though, and for Polyjuice specifically, one of the ingredients has to be picked at the full moon, so I think I'll just headcanon that it has to be fresh, and then the potion lasts for one year from that full moon - still highly convenient, but not excessively so.

 

Maybe Felix does go bad... but fortunatley, any given drinker is just really lucky.

For a complete list of such quirks, see The Potioneers' Paradox

On the other hand, whatever potion was defending the locket horcrux worked just fine over a decade after the fact, and it wasn't in a sealed container. So any given potion can do what you want: but I believe there's enough evidence to conclude that not all potions are ageless.

 

I feel as though this may also just be Snape being a dick... he'd definitely relish having Lupin dependant on him every full moon.

Both of these statements confuse me. Are you saying that the luck is effective before they've drunk the potion? And I have no idea what the Potioneer's Paradox is... I feel like you're joking but I'm unsure

 

It was a jest. But I think it would fit the HP verse that Felix could, in theory, go bad... but it just so happens the drinker of any given batch is lucky and his batch of fine.

 

Then again there's also this exchange:

Honestly, this could mean that either Wolfsbane can be made in larger quantities and kept, or that Snape sells the excess or uses it within that frame, but I'm inclined to think the former.

But shelf life does seem to have an effect, since in HBP, when Ron was doused with the love potion, Slughorn comments:

 

Is there any indication in canon that a wizard can control how loudly or quietly they apparate? I read a lot of ff authors allowing silent apparition, but I can't remember there ever not being a noticeable sound accompanying apparition.

 

I looked around, and it seems like one of those things that Rowling never clarified but based on the evidence it seems like you can control it with skill.

In Philospher's Stone, when Dumbledore first drops Harry off at the Dursleys, he 'appeared so suddenly and silently you’d have thought he’d just popped out of the ground.' There's the possibility he was walking and then took off his invisibility, but that's unlikely. Fred and George do it with a 'loud crack'. Arthur does it with a 'soft pop'. Narcissa does it with 'a very faint pop' but Bellatrix's is a 'louder pop' in comparison.

 

Can you take a potion to get in touch with your 'inner apparition noise'?

I remembered that Fred and George did it with a loud crack, but I couldn't remember any hard evidence that this was because they were n00bz, or because they just like making loud noises.

Likewise, I could imagine Bellatrix being loud for effect.

 

There's two countering realities to that point (realities that counter each other, I mean). First. if we were to look at the scientific side of it, the "pop" is the sudden air displacement—the pressing out of air at such a high speed that it compresses the air to form a shockwave that dissipates as it moves out.

The second reality is the literary world. The "pop" is in relation to characterization. Dumbledore is the narrative equivalent of Merlin. Thus, his magical ability and "famed intellect" are so far beyond others he cannot be touched. Others have not the ability to know what he knows, thus, they do not know when he Apparates to a location. Fred and George are characterized as two wizards who are always drawing attention to themselves through pranks and other things. Thus, their characterization is found in their large pop. Narcissa has very little to do in the narratives. She is often silent and only once does she take center stage in a scene, and even then, she is somewhat upstaged by her sister. That is why her "pop" is very feint—it matches her role in the story. Narcissa overshadows her in that she is louder, more demanding in the scenes they are in together, and louder in her support for Voldemort. Thus, her pop also overshadows Narcissa.

So, the question on controlling the noise depends on a couple of things. Based on characterization, no, they cannot control it as it is a mirror of who they are. Based on science and the manipulation of gases, yes, they can control it by learning how to displace air differently (more slowly or sluffing it off somehow, think a silencer on a gun).

Therefore, the answer is based on your starting point. Are you asking pure canon? Then no, because the narrative logic says its tied to character. Are you asking about the narrative world in which the author is dead? Then, yes, it is possible, especially when considering the physical properties involved.

 

What distinguishes animagus transformation from self-transfiguration?

We can infer from canon that an animagus only has one form. James is always a stag and is always going to be a stag. Sirius a grim. Minerva a cat, Rita a beetle, etc. etc. However, we also know that wizard's can do self-transfiguration.

Krum partially self-transfigures into a shark, but there's no suggestion that this would be his animagus form and he's only half way to accomplishing it. Likewise, I doubt very much that Slughorn's animagus form is an armchair. Draco doesn't transfigure himself into a ferret, but obviously, one wizard can turn another into an animal and there's no suggestion this is in any way related to what they would be as an animagus.

So what is it? What is it that differentiates James turning into a stag and accomplishing something that supposedly only a tiny fraction of wizards ever do... and transfiguring into any animal he damn well pleases?

 

I would guess the lack of needing to do a spell. We never see McGonagall having to wave her wand to transform, it's just innate. So I guess once you become an animagus you can transform at will.

When Draco was a ferret, Moody cast a spell on him.

 

Slughorn's form is a chair. Malfoy would've been stuck as a ferret and unable to undo it. Krum was a partial transfiguration on purpose to prevent getting stuck. He was still influenced by the shark instincts though and tried to eat Hermione off the post.

 

My only guess would be that it's a case of time. Slughorn would have turned back eventually, Malfoy too and Krum would have had a time limit in mind.

Possibly an awareness issue too. Slughorn, for example, could have been relatively aware of his form as a chair with enough control to pull back if needed or he knew he'd only have to wait for a certain time.

Malfoy had no control but as he was under another wizard's spell there could have been a time limit.

I say this and then remembered something that fucks it up.

Most people here have read Fantastic Beasts and where to find them, right? Not the movie book, the originally World reading day charity book.

In that it mentioned that a clan of wizards from Scotland were turned into Quintapeds by rival wizards and stayed that way with the island becoming unplottable because of the danger.

That brings up a question. While transfigured did they breed like fuck before the time limit ran out? Or did they just remain transfigured?

In HBP there was a skeleton of a five legged creature in a cage. All evidence available says that could be a Quintapeds which would point to life cycles and breeding. Unless death by spell, in which case why stop to bring the skeleton?

I have answered nothing, just created a more mind bending question.

 

Piggy backing this from that strong and weak points thread:

Did "imperius chaining" happen in the series, i.e. a person under the imperius curse casting the imperius curse and so on?

 

I think so: Draco Malfoy --> Rosmerta --> Katie Bell

Don't remember if there was a chain involving the Crouches