"How did these items get made if there's no way to learn magic? Are the magicians homeschooling their children and not writing any books? How did you learn?"
"Half this stuff is antiques," says the shopkeep. "Look, asking me a dozen times isn't gonna make the answer more to your liking. I don't have Hogwarts in the basement, deal with it."
"But where do you get the stuff that isn't antique - who made the Avalon itself? - isn't anybody panicking about the medallion supply? -"
"Kid, nobody knows how to make medallions."
"But some people apparently know how to make luck charms and protection amulets!"
"I'm not going to give out my suppliers' personal information. I wouldn't do it even if you weren't annoying."
"There have to be books -"
"Does this look like a library to you?"
"Yes, yes we are. Ren said she'd get me a laptop if I got a spell to work so I could have my spreadsheet portable, so that'll help, I'll be able to bring it here."
"Wonderful." He looks at the tea. "We should probably drink that before it goes cold."
"I hope they're not too terrible. Jaromira talked me into looking up a recipe rather than just going out to a store."
"So last night I got a little ahead of myself and I compiled a list of meanings - not runes, just meanings - that I think would go well in an invisibility spell, but I think you should do something similar on your own so we can compare without you being contaminated by my ideas."
Eventually, the tea and cakes are done. "Oh, I just realized. We never refilled the wax tablet to see if the ink or the grooves counted for the spell."
Kanimir takes the tablet over to where May filled the kettle, rinses it out, decides the day's balmy enough he doesn't need a sweater, takes his off, and dries it. Then he carries it back over to the table, puts the kettle (currently containing warm but not boiling water) on the tablet, and incants again.
"Okay, that's twice on the same tablet, so the ink worked and the scratches worked."
"So if the ink worked separately, that most likely means a refill would work as well. Let's try it with water now." He rinses out a teacup and uses it to fill the scratches. "Would you like to do the honors?"
"...This has all sorts of implications. We might be able to make scrolls with invisible runes, if we drew them with the kind of inks intended for temporary marking that vanish after awhile."
"I meant the fact that water worked specifically rather than the fact that the grooves are reusable, but yes, we absolutely can."
"I would have said watermarks but I don't know if we could get those precise enough."
"But we can mass-produce magical objects. We're going to drive that man so far out of business he can't find his briefcase."
Cackle. "I want a Ring of Gyges. Well, probably a Necklace of Gyges, because, shapeshifting, but you know what I mean."