Adding Absorbency

If more absorbency is needed, here are some options.

  • Cotton flats, prefolds, muslin cloth, trifolds, tea towels, face washes. These are cheap, easy to wash and dry quickly.
  • Bamboo or help inserts and trifolds, these absorb a lot.
  • Microfiber inserts. These are like sponges, liquid will absorb but it will start seeping out once compressed.

Microfiber on top of bamboo insert/hemp/cotton flat/cotton tea towel/a prefold/ trifold works well. The insert below catches any compression leaks from the microfiber that sits on top. Microfiber should not go directly against the skin, it can cause irritation.

If more absorption is needed use any of the options above, bamboo, hemp and cotton absorb more liquid than microfiber.

Microfiber and bamboo

Absorbency

Some absorbency measurements:
Bambino Mio size 1 prefold 110g
Bubblebubs cotton muslin flat 70x75cm 150g
Designer Bums small snap in insert 65g large anchor insert 145g
Real Nappies Crawler prefold 251g
Econaps small insert 60g large insert 85g
Dickies Terry Towelling Flat 282g
IKEA Haren hand towel 250g
Alva 3-layer bamboo insert 115g
Bamboo trifold inserts 180g
IKEA 70x70cm muslin (from baby section) 195g

Prefolds and flats
Cotton flats and prefolds

Inserts made from bamboo, hemp or cotton can be soaked overnight to help increase absorbency and then washed on a regular cycle with detergent. These fabrics will continue building absorbency with use, change more frequently during this time.

Why does prepping make such a difference?

The surface area of the fibers increases over time with washing (ie friction), the fibers become looser and micro piling occurs. The greater the surface area, the more absorbency potential [1], [2].

Covers and microfiber inserts can be washed once with detergent prior to use.

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.[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

Urine output in children

Newborn babies have very small bladders, about 20-30mls, or just bigger than a metric tablespoon [1] [2] [5].  Children’s bladders get steadily bigger as they age, with a shift in how fast the bladder grows around age 2.  Girls have bigger bladders than boys [2].
How babies pee also differs among children of different ages.  Neonates urinate more often and at a higher pressure than older children [3] [4]. 

This pattern of when children urinate guides what absorbency is needed in reusable nappies. 

Newborns need very small nappies (both because the child is small and because urine volumes are small) but the child will need changing frequently.  This is also due to when the child will poo as well as how much and how often they pee.   Many newborns poo before, during and after feeds.  Typically newborns outwet nappies before they outgrow them, and more absorbency needs to be added to nappies or they will leak. 

As children get older, their bladder capacity increases, and the amount they can pee increases, children require nappies with more absorbency.  This peaks at about six months of age, which is the largest a child is when all of their nutrition is in liquid form.  
After around age 2, children develop the ability to “flood” nappies, when they are dry for long periods of time (2-3 hours) and then can let go of a very large volume of urine all at once.  Almost all OSFM nappies will require boosting for toddlers if a nappy is to last 2-3 hours.

[1] Bachelard M, Sillen U, Hansson S, Hermansson G, Jodal U, Jacobsson B: Urodynamic pattern in asymptomatic infants: siblings of children with vesicoureteral reflux. J Urol 1999 162: 1733–1738

[2] Kaefer-M et al.  Estimating normal bladder capacity in children. J Urol. 1997 Dec;158(6):2261-4.
https://www.jurology.com/article/S0022-5347(01)68230-2/fulltext

[3] Sillen U: Bladder function in infants. Scand J Urol Nephrol Suppl  2004 215:69–74

[4] Hjalmas K: Urodynamics in normal infants and children. Scand J Urol Nephrol Suppl 1988  114:20–27

[5] Wen JG, Tong EC: Cystometry in infants and children with no apparent voiding symptoms. Br J Urol 1998 81:468–473.