Chūnjuǎn Pí (春卷皮) is the spring roll wrapper itself, not a finished roll: a thin, pale sheet of wheat-based dough used to enclose a filling that is then rolled and usually fried. This article covers the wrapper on its own terms, because its thinness, strength, and moisture decide what any cook can build from it. The defining trait is a contradiction the sheet has to resolve: it must be thin enough to fry up shatteringly crisp or stay pliable for fresh rolls, yet strong enough to wrap a wet filling tightly without tearing.
The wrapper is made by working a soft, very wet wheat-flour dough against a hot flat griddle so a thin film cooks and is peeled away as a near-translucent round, then stacked and kept covered so it does not dry. Some styles use a thinner, more delicate sheet for fresh, unfried rolls and a slightly sturdier one meant to be deep-fried. Good wrappers are uniform in thickness, free of holes and dry brittle edges, supple enough to fold and seal without cracking, and they fry to an even blistered crispness rather than scorching in patches. The failure modes are plain. A sheet rolled or cooked too thick fries up tough and bready instead of crisp and stays doughy at the seam. One that has dried at the edges cracks the moment it is folded and splits in the oil, letting the filling leak and the wrapper absorb grease. A sheet that is too thin or too wet tears under any substantial filling and cannot be sealed. Storage matters as much as the make: stacked sheets that are not kept moist fuse or harden and become unusable, which is why they are handled fast and covered with a damp cloth.
From there it shifts by how it is used rather than by ingredients added to the sheet. Filled with shredded vegetables, glass noodles, or seasoned pork and deep-fried, it becomes the familiar crisp spring roll, and the same wrapper rolled around fresh fillings and left unfried is the soft version. Sealed at the edges with a flour-and-water paste, it can be parceled tightly enough to hold a juicy filling; left loosely folded it opens in the fryer. The wrapper is also distinct from the thicker pancake used for duck and the rice-flour sheets used in other rolls, each a different sheet for a different purpose. Where it is wrapped, fried, and served as a complete dish, that roll is its own preparation and deserves its own article rather than being crowded in here, since this entry is about the sheet that makes the roll possible.