Cotton is the oldest pillow fill still in ordinary use and the one most often described in the vaguest terms, which is the gap this reference exists to close.
Where to start
What makes cotton behave the way it does in a pillow?
Staple length, construction and packed density, in that order, and every other property people notice follows from those three.
A cotton fill does not loft the way a hollow or crimped fibre does. It compresses, it packs, and how fast it packs is a function of how it was built rather than how much was put in.
Defining those terms properly is most of what this site does.
What does this reference define?
Six things, each with its terms defined on first use and its limits stated in the same sentence as its number.
Fibre length, where it comes from, and what it changes in a fill rather than in a yarn.
Batting, shredded and continuous fibre treated as three different objects.
How filled weight becomes loft and resistance, with the arithmetic shown.
What compacts, how fast, and which part of it recovers.
Whether to, at what temperature, and what drying does to the fibre.
What an organic textile standard reaches on a finished pillow, and what it does not.
How are claims handled here?
A claim arrives with the thing that supports it, or it does not arrive. Most answers here are conditional and say so.
The honest answer to a large share of pillow questions is that it depends. Each page states what it depends on and in which direction, which is more useful than a verdict.
Latest guide
Is batting or shredded cotton fill better on night one and night three hundred?
Two cotton pillows can carry identical labels and feel nothing alike. One is built from carded sheets of cotton batting laid in layers, and the other is packed with loose, torn tufts of cotton. Most people notice the difference th