What Materials Absorb Fastest?

Speed of Absorption Testing

Don’t hate me, but I’ve never had much of a problem with leaking cloth diapers. I like to attribute this to the following factors: (1) My baby has the perfect body type, (2) My impeccable instincts lead me to only the very best cloth diapers, (3) I’ve devised a fool-proof laundry routine, and (4) I always know precisely which insert or combination of inserts to use for every occasion.

I kid, I kid. I’m sure it’s mostly just dumb luck.

For parents who are having trouble with leaks, though, it can be a huge hassle. You’re dealing with a baby who should be sleeping but instead is awake, crying, and wet. You’re making frequent clothing changes for the baby (and possibly having to change your own clothes and the sheets as well). While doing all that extra laundry, you find yourself wondering, “Is the diaper repelling? Is it not fitting properly? Is my baby just an unusually heavy or fast wetter?”

If you have eliminated the possibility of repelling or a fit problem, you can experiment with different types of absorbent materials.

I’ve always heard microfiber described as a “fast-absorbing” material, but wasn’t inclined to believe it. It’s a synthetic material, and if you’ve ever thrown a microfiber insert in a bowl of water, you might have noticed that it will float happily on the surface of the water for quite some time before succumbing to the fathoms below. (Wait, what?! You mean to tell me that no one else does this for fun?!)

Floating Microfiber

“Microfiber Magic Carpet Ride” – cue music from the Aladdin soundtrack.

I decided it was high time I test the speed of absorbency of various cloth diaper materials for myself and then spread the word. You know, for the edification of cloth diapering parents everywhere. And to satisfy my own curiosity.

The testing method involved emptying a syringe of 50 mL of water into a tube that is anchored and weighted where it touches the insert (to simulate a good, snug fit on baby). I simply timed how long it took each insert to absorb the full 50 mL of water.

Testing Method

The lineup of test subjects from my own personal stash included two synthetic-fiber inserts and two natural-fiber inserts. The results? Yeah, totally proved my “slow-absorbing microfiber” theory wrong. Both microfiber inserts absorbed the water significantly faster than the natural-fiber inserts:

  • 19.1 seconds – bumGenius microfiber
  • 21.0 seconds – Rumparooz microfiber
  • 27.7 seconds – SoftBums bamboo
  • 30.0 seconds – Thirsties hemp
Speed of Absorption Test Results

Left to Right: Thirsties large hemp insert (55% hemp, 45% cotton), Rumparooz one-size 6r microfiber soaker (80% polyester, 20% polymide), SoftBums one-size bamboo pod (70% organic bamboo, 30% organic cotton), and bumGenius one-size microfiber insert (microfiber terry).

Now don’t go hating on the natural fibers just because they’re slower on the uptake. Natural fibers are more breathable, less prone to build-up problems, and often better for babies with sensitive skin. And for lucky folks like me who don’t have leak problems, speed of absorption doesn’t really matter. I just wanted to know!

What is your favorite type of insert and why?