Although Slughorn has warned them that some of the materials are red herrings, they have been provided with a variety including stinging nettles, sand, ragweed, some sort of mucus with a smudge on the label where it might describe the source, corn starch, and unicorn tail hair.
Okay there is just no way the unicorn tail hair has anything to do with it. Now, stinging nettles and ragweed might have something to do with irritation, but sand is stereotypically linked to the fabrication of pearls—though he has in fact found out that they're not nearly as common sources of pearls as most believe. And as it is, given that a grain of corn starch has a higher probability of actually getting stuck inside an oyster...
His first guess goes along the line of stinging nettles as a metaphor for "irritant" and as little corn starch as he can get as a metaphor for "microscopic." He eyes the unicorn tail hair again with suspicion but decides not to question himself this early in experimentation—counterintuitive ideas will have their turn after the intuitive ones have all failed.
Now if he coats those with mucus... should he burn them? He feels like he should burn them.
What's Miranda even doing?
...wait aren't they supposed to actually do things here he thought they were supposed to actually do things instead of just figuring out what they wanted to do and then waiting to be corrected.
They will be doing things after Slughorn has made sure none of their ideas are total disasters. They have five more minutes left in the first section of the class period.
Oh.
Yeah he was definitely going to be the first one in the Hospital Wing, wasn't he.
More ideas! Using sand instead of corn starch because it's ingrained in people's minds that sand is related to pearls, using sand on top of corn starch for the same reason, he cannot think of a single good way to relate unicorn tail hair to this so he mostly doesn't, he also permutes the irritants...
Miranda raises her hand, as does a third-year Gryffindor.
Well, if you're going to be wrong, better be wrong spectacularly and in front of a lot of people. He raises his hand as well.
Miranda stands up. "I think the cornstarch is a red herring. I'm not sure any of the other things are but my procedure uses stinging nettles for irritation, sand for time, and unicorn tail hair for beauty, and I'm mostly guessing for the actual steps but I'm thinking wrapping the oyster in the nettles, burying it in sand or maybe dribbling the sand into a pile nearby, all in a circle of a unicorn tail hair, followed by burning the nettles away from the oyster?"
"Nicely done for a first attempt," says Slughorn. "Five points to Ravenclaw for a plausible procedure, although before you actually try it I'll want to make a small few adjustments. Mr. Woods."
"Either stinging nettles or ragweed for irritation, I didn't see any particular reason to choose one in specific. Actually, saying this out loud, I'm thinking maybe using both because one of the things they have in common is being irritants so together they might be more obviously about that than about something else. I didn't think the corn starch was a red herring, my main thought about it was that a single grain is really tiny so it could relate to the fact that irritants that produce pearls are typically microscopic. I didn't think of time at all, and the only reason I saw for sand was as something to reinforce the idea that 'this will become a pearl' because sand-makes-pearl is so ingrained in people's mind. Erm. I thought the unicorn tail hair was a red herring, and that the unspecified mucus could correspond to the process of creating a pearl.
"So what I thought for the actual steps would be wrapping sand and corn starch in nettles and ragweed and binding it all together with the mucus, then burning it and sprinkling the oyster with the ashes."
"How do you propose to wrap sand and corn starch in nettles and ragweed?" asks Slughorn.
"Oh, the idea was putting the particulates on the leaves and making a little envelope with them."
The other three students' ideas are all as different as Sadde's and Miranda's. Apparently there are a lot of plausible ways to do the thing. No two people agree on which ingredients were red herrings; the Gryffindor even thought of something to do with the banana leaf.
Slughorn gives a brief and jolly summary of how this is the beauty of alchemy and he hopes to see everyone's creativity burgeon over time even as they learn more constraining principles that will keep them out of the hospital wing. And then Miranda is told that she needs to dribble her time sand onto some of the mucus, and Sadde needs to not irritate his oyster to death and remove two of the three representations, and so on and so on - and now that no one is about to set their eyebrows on fire, they may proceed!
Yay for not setting eyebrows on fire! He chooses to remove the sand and the ragweed, and proceeds. He has practised being careful and delicate while becoming good at Potions so it's not too difficult to do the thing with the leaves.
Really different kinds, too. Sadde's is a freshwater-looking thing of irregular shape. Miranda's came out gold; one of the other students got five seed pearls; another got something pink, and the second-year Hufflepuff - surprising even Slughorn - somehow managed to get a chunk of mother-of-pearl instead.
They are assigned essays on why they got the specific results they did, another five chapters of reading, and sent home.
Well he's not dissatisfied at all with his pearl—he always thought spherical pearls looked so boring anyway—but he's a tad envious of Miranda's gold one.
"I have nnnno clue," he says. And then, as usual when he starts with that, he follows with: "Actually, I think the most obvious thing might be that the shape of the leaf envelope might have influenced stuff. Maybe if I'd made a neat little sphere of mucus around sand and corn starch it'd have been better."
"Ooh, I like it. I'm going to look up where gold pearls come from to see if that gives me ideas, I don't have a clue."
Sadde actually might know something related to this! "If I'm not mistaken gold pearls are usually a kind of cultured pearl?"
"Are they? But the oyster would still have to make them gold, even if they were started on purpose."
"Yeah but I mean, cultured pearls are kinda different than wild pearls, though I don't remember how exactly. I can show you the book where I read about this, I haven't returned it to the library yet."