Prepping new cloth nappies before use

Wash new nappies once before use. They can be added to other laundry, ideally white or light coloured items to prevent picking up colour run.

Photo by Dan Dennis on Unsplash
| (updated )

Wash new inserts once before using them, and change them more frequently as they build absorbency. Inserts that are made of man-made fibres do not change absorbency when they are washed.

The surface area of natural fibres increases with washing. During the friction of the wash cycle, the fibres become looser and micro-piling occurs. This increases the material’s surface area, increasing the absorbency potential.

You might have been told you need to ‘prep’ (prepare) new cloth nappies by washing them several times, or by soaking them overnight. They only need to be washed once. Simply change them more frequently as they build absorbency.

How absorbency increases with washing

During washing, natural fibres become looser and micropilling occurs. This increases the surface area, and when the surface area increases so does the absorbency potential.1,2

Scanning-electron-microscope-images-of-the-silk-fabrics-a-d-before-washing-b
Scanning electron microscope images of the silk fabrics: (a), (d) before washing; (b), (e) washed with ultrasonic energy; and (c), (f) washed with washing machine for 15 cycles.
scanning electron micrograph of commmon fibres
Electron microscope image of common fabric fibres

References and further reading
  1. L. Quaynor, M.Takahashi M. Nakajima 2014, Effects of Laundering on the Surface Properties and Dimensional Stability of Plain Knitted Fabrics.
  2. C. Ganser, P. Kreiml, R. Morak, C. Teichert 2015, The effects of water uptake on mechanical properties of viscose fibers.