"Everyone gather 'round," said Snape, his black eyes glittering, and watch what happens to Longbottom's toad. If he has managed to produce a Shrinking Solution, it will shrink to a tadpole. If, as I don't doubt, he has done it wrong, his toad is likely to be poisoned." (Harry Potter and the Prisoner of Azkaban)

It seems that the point of Shrinking Solution is to physically shrink the size of beings (similar but opposite to Swelling Solution that Harry exploded in Goyle's cauldron in The Chamber Of Secrets to let Hermione steal ingredients).

But a tadpole is not just a small frog - it's a young frog.

If the solution makes beings younger, shouldn't it be a rejuvenation solution and not Shrinking Solution?

Is there anything else in canon addressing this weirdness?

  • 1
    Just because it's called "Shrinking Solution" doesn't mean that's exactly what it has to do. If the only information we have about its effects is what Snape says here (Is it? I'm not going to check every line of the books.), then we should conclude that physically shrinking things is not its point.
    – jwodder
    Commented Mar 14, 2013 at 4:03
  • Maybe Snape said "tadpole" purely as an expression to describe a small (shrunk) frog, rather than, well, an actual young frog.
    – Saturn
    Commented Mar 14, 2013 at 16:45
  • @Omega - Snape is smart. He doesn't make stupid mistakes. Commented Mar 15, 2013 at 5:25
  • @DVK: Wait, I didn't say it was a mistake. I meant to say it was just an expression - as in, almost a joke. Nothing serious. For instance, it would be like Snape calling a small student a dwarf, not because of their race, but rather because of their height. So the same goes for the frog - Snape calling it a tadpole not because of the age, but rather because of the size.
    – Saturn
    Commented Mar 15, 2013 at 14:50
  • @Omega Except that, IIRC, the frog actually does turn into a tadpole, so Snape was being literal.
    – commando
    Commented Mar 15, 2013 at 14:53

2 Answers 2


This is a common device throughout fiction-- the inconsistency between differing usages of a word.

Technically a tadpole is a "small frog" much as a baby is a "small person:' the age difference does decrease its size, and it certainly doesn't change its species, even we don't normally think of tadpoles as frogs.

The only in-universe explanation I can imagine is that the shrinking solution operates not upon logical principles of changing the size of those which it effects, but is literally a shrinking solution: it operates upon the meaning of the word small, with all of the inconsistencies and nuances of human speech. This is magic after all, and it has been consistently demonstrated throughout the series that mispronouncing a spell or lacking concentration as to your goals can produce disastrous (or at least unexpected) results. This seems to indicate that magic in the Harry Potter universe is -to a certain extent at least-dependent on the user's intentions and/or expectations. This isn't quite "cannon", but I believe it to be a logical inference from canon material.

To be frank however, this type of logical inconsistency is so pervasive in science fiction and fantasy alike that I highly doubt that there is a true canon explanation.

  • Given the sheer amount of canon info available (interviews, Pottermore, old jkr site, upcoming Encyclopedia), I would not be surprised if there's a true canon explanation. Commented Mar 18, 2013 at 1:02
  • @DVK I do not deny the enormity of material available on the subject. However, my main point was that this phenomenon is so ubiquitous in fiction that it is unlikely to be considered. Commented Mar 19, 2013 at 3:44

Maybe the term "shrinking solution" indirectly means shrinking/changing something back to an earlier form, for example a human would become a small child, a frog becomes a younger frog, ie a tadpole. Nobody really knows how old the frog is that he uses which may sound unrelated and farfetched but if this frog hasn't long since been a frog then it may be that this is why it became a tadpole. If you used a chicken that had recently become fully grown, it would probably turn back in to a chick. Maybe it was called shrinking potion to make the name roll off the tongue a little easier rather than anti-aging potion etc.

(I apologise if this made no sense - it sounded better in my head)


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