Saturday, May 14, 2016

Testing Absorbency for the Flats and Handwashing Challenge

I'm preparing to participate in the 6th Annual Flats and Handwashing Challenge next week, which means that when we diaper, we will use only flats (and covers) all week, and we will handwash them.  Normally, we use some flats and some prefolds, so I am doing some absorbency testing to ensure that when I swap out prefolds for flats in the daycare and overnight diapers, there are no surprises.

Water Weight
DiaperDry Weight*Soaking Wet*% Dry WeightHand Wrung*% Dry WeightMachine Spun*% Dry Weight% Water Removed with Hand Wringing
Old Prefold** 2.58320%4.2168%280%48%
Ratty Prefold**1.85.9328%3.1172%1.689%47%
DIY Hemp3.68.8244%4.7131%2.981%47%
DIY Rayon***2.36261%2.295%

Cotton Average329%161%80%51%
Cotton Standard Deviation12%15%6%6%
Hemp Standard Deviations from Cotton Average-7.1-2.10.01-0.7
* All weights in ounces
** All my prefolds are previously diaper service prefolds that are apparently past their useful life as diapers according to the diaper service.  I got them really cheap at an automotive store. The "old" one is a specimen in pretty good shape, the "ratty" one has lost many of it's layers and is kind of shredded on the outside, but it still works okay inside a pocket diaper.
*** DIY Rayon is a 22x26 inch flat made from an old Modal bedsheet, similar material to Bamboo Viscose, which is a popular material for flats. Measurements done on a different day with altered methodology, so not really a good straight up comparison.


  1. Dry Weight: Weighed all the diapers dry.
  2. Soaking Wet: Added water to each diaper in a Pyrex baking pan until soaking wet.  Held by corner until stream coming off slowed to drips.  Weighed again and subtracted off dry weight using terr function.
  3. Hand Wrung: Wrung out flat by hand and weighed again, again subtracting off dry weight using terr function.
  4. Machine Spun: Put all diapers in the washing machine for a rinse and spin cycle.  Weighed again and subtracted off dry weight.  (Didn't use terr this time because all diapers were rinsed and spun together.)
I believe that in real life, a diaper would hold somewhere between the "Soaking Wet" amount and the "Hand Wrung" amount without leaking.  The closer it is to the Soaking Wet level, the more likely one might see compression leaks.  Below the "Hand Wrung" level, I wouldn't expect any risk at all of compression leaks.

On the flip side, the more water I can hand squeeze out of a diaper, the more easily I will be able handwash it (squeeze out soiled water, soapy water, and rinse water).  This has me leaning toward using the Gerber flats as much as possible during the challenge, although I don't own enough of them to send to daycare, as I would certainly need to double them up to send to daycare and I only own 10 of them.  I was already leaning toward using the Gerbers as much as possible because the thin fabric seems like it will dry fastest.

We normally use the "old prefolds" for daycare, and will replace with Osocozy flats.  These will be stuffed in pockets, as that is what daycare expects.  

Overnight we normally use one of the ratty prefolds with a DIY hemp flat.  My feeling has been in the past that hemp is overrated because it is so slow to absorb.  As you can see, after a rinse and spin in the washing machine, it's absorption by weight was similar to that of my cotton diapers, but in the experiment at the sink, it held significantly less by weight.  It held more overall than the other diapers because the material is thicker and the flat itself is bigger.  I think I will try skipping hemp entirely for the challenge and see how it goes.  I can always add it back if needed.

Overnight I think I will instead try either 3 Gerber flats or 1 Osocozy flat and 1 Gerber flat.  I feel like the Gerber flats will be easiest to handwash because they are so thin and seem to be easiest to wring out.

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