Monday, September 29, 2014

Anyone want to explain the chemistry of diapers?

This week's C&EN also brings us a rebuttal to a recent Newscripts column on diapers:
...Newscripts recently waxed enthusiastic about Charlie’s Soap, “a laundry detergent brand that is popular among folks concerned about laundry residues” (C&EN, July 7, page 40). Charlie’s Soap is good, we are told, because it contains fewer ingredients than other detergents. It seems to contain only soap and soda ash. 
Charlie’s Soap might actually work—if you are washing in distilled water. That would include approximately none of us. Any hardness in the water at all will precipitate the soda ash as calcium and magnesium carbonate. Even worse, the soap will precipitate as scum. 
Those diapers you were trying to wash to a residue-free condition will be loaded with sharp-edged crystals of calcium carbonate, which will abrade the fibers of the diaper, shortening its life. Additionally, that residue will be alkaline in nature, and hence irritating to the poor child of the ignorant parent. The diapers will also be loaded with soap scum that, in the short term, will make them appear gray and dingy. In the long run, the accumulated scum will make the diaper harsh to the feel and no longer absorbent. 
Formulating any kind of product to the fewest number of ingredients is a truly bizarre, and wholly irrational, goal. Ask anyone who has ever said it for the reason why. I have yet to hear an answer to that question. Mother Nature doesn’t hold herself to such an unrealistic goal. In a recent issue of Inform (published by the American Oil Chemists’ Society), the ingredient list of a common chicken egg was published. The list, almost certainly not exhaustive, contained about 100 different ingredients. 
Unfortunately, the statement about the fewest ingredients goal is never challenged. It’s the kind of thing you would expect to see from Consumer Reports or Greenpeace. But it’s not the way to get things clean. It’s disappointing that C&EN reported it unchallenged. 
I could go on and on about this one little story. Dryer sheets add so little hydrophobic wax to fabrics that they have virtually no effect on absorbency. (Rinse-cycle fabric softeners are a different story.) The ammonia stink from diapers is not due to microbes not removed during washing. The diapers do not come out of the dryer sterile, of course, but they are sanitary. The microbial load comes from what the baby deposits in the diaper. 
The next time you need to know how to get something clean, contact Walt or me. Don’t depend on someone who is trying to make a buck by pandering to the public’s fear of chemicals. 
Dave McCall
I don't really know if calcium carbonate deposits happen in diapers that have been washed with Charlie's Soap -- anyone up for doing some wet chemistry with diaper residues? I didn't think so.

As someone who has been through the cloth diaper wars with 2 kids, the problem really seems to arise from two places:

Diaper rash: Diaper rash shows up mysteriously with your kid, so you start by changing one parameter (the laundry soap). It either goes away or it doesn't, and then you start changing multiple parameters, including having the kid run around naked. Finally, you settle on something that seems to work for you.

Diaper wear: Cloth diapers are a rather high capital cost, so you're tempted to keep re-using them. As the diapers get older, they seem to absorb less and less (as the kid seems to produce more and more waste). So, you start changing the washing routines (detergents, hot/cold washes) to start removing whatever seems to be building up in the fabric... or you buy new ones.

There's probably a lot of science out there about this that I don't know about -- readers?

One final note: I thought it was interesting for Dr. McCall to address the root cause of these concerns to be chemophobia on the part of parents. I tend to agree with him; however, I suspect he misses the emotional appeal of having fewer chemicals touching the nether regions of one's children. Sure, simplicity in diapers is probably a fallacy, but the temptation is understandable. 


  1. Off topic - but living in SoCal, we successfully managed to avoid the whole diaper wars in that disposable diapers are unusually the preferred environmental option. Water is more scarce than landfill.

  2. Diaper wars? Are they like immunization wars?

  3. diaper rash is not typically caused by allergies (to laundry detergents) but by the changes in microbial flora in gut, and on the skin. Diaper rash often appears when the nursing mother or the child were treated with antibiotics or after solid food was introduced.

  4. Well I don't know about you guys but I wash in DI all the time...

  5. "Ray! You take that diaper off your head, you put it back onto your sister!"

  6. I don't have kids myself, but on another internet forum witnessed a very heated, catty back and forth about detergent build up/ammonia build-up, re: whether it existed and how to prove or disprove what was going on with the diapers. People take their diaper washing practices very seriously, apparently.

    1. A good quality (and complete) set of cloth diapers runs in the ~$350-$400 range, I believe, and turns your home into a small laundry facility. I could imagine people having very strong opinions about it...

  7. Considering the whole breast-feeding/formula-feeding discussion (is there a league for cloth diaper use?), discussions over diaper usage getting out of hand seems unsurprising.

    Perhaps the lesson is that everyone knows how to raise everyone else's children except their own.

  8. We've (specifically my daughter) been having cloth diaper rash issues, possibly stemming from Charlie's Soap. She gets a rash with cloth diapers, even when they've been stripped (borax/Calgon/sodium bicarb wash). Given that babies are tiring, I hadn't thought about water hardness as a factor with the soap and just went based on recommendations of mommy fora (which are incredibly opinionated and catty places).

    As far as I can tell it's either yeast-related, detergent-related, or both. It's a pain to figure out, though.

  9. In general,participants in the diaper wars are much more recptive to basic chemical and biological facts.

    I tried Charlie's once and it caused a terrible rash, which was remedied with a vinegar rinse. It wasn't a yeast rash, so it muct have beenthe pH. Being a winemaker, I pretty much have one trick in my book whenit comes to cleaning. Luckily an acid rinse is pretty much always great for the skin.

  10. Sorry for the typos above, my ipad isn't playing nice with comments.

    Denny, have you tried All free and clear, with a vinegar rinse?


looks like Blogger doesn't work with anonymous comments from Chrome browsers at the moment - works in Microsoft Edge, or from Chrome with a Blogger account - sorry! CJ 3/21/20