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
Detroit

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.