Mercerized Yarn and Unmercerized Yarns - What's the Difference?

It all comes down to the 'Stretch'

Mercerized Cotton

Mercerized cotton fibers are longer, more stable, and have more of a twist which means less pilling.  The process of mercerization developed by John Mercer in 1844, improves the dye qualities of cotton yarn when it’s run through an alkaline bath under tension. During this process the fibers change making them smoother, durable, brighter in color, and more stable. This means that projects created with mercerized cotton yarn will retain their beauty longer, stay vibrant without stretching in finished projects. Mercerized cotton will also not absorb water as quickly therefore it’s perfect for dishtowels and washcloths in addition to garments.

Unmercerized Cotton

Unmercerized cotton fibers are typically shorter, and as a result, the yarns produced from them are fuzzy from the ends sticking out in various directions.  Unmercerized yarns have the greatest amount of fuzziness.  Using unmercerized cotton yarns lead to softer projects that feel nicer next to our skin. However projects may not last as long because the cotton fibers have not undergone the structural changes as mercerized cotton has therefore are not as durable and can stain more easily.