Chemical Marketplace: Bar Soap vs. Liquid Soap

One of the dirtiest campaigns in recent memory is over. So let us cleanse ourselves by turning our attention to a new topic: soap. Why? Turns out, it's a green issue, both environmental- and pocketbook-green.
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More than 80,000 chemicals are produced and used in the United States. This is one of their stories.

Post corrected December 4, 2013.

One of the dirtiest campaigns in recent memory is over. So let us cleanse ourselves by turning our attention to a new topic: soap. Why? Turns out, it's a green issue, both environmental- and pocketbook-green.

Soap: It does a body good. But is it soap?

Let's face it: We are a society that likes to be clean. And it's not just out of fastidiousness. Doctors now recommend that we wash our hands a gazillion times a day (and sometimes use hand sanitizers) to ward off the flu and other medical calamities. And all that washing translates into a lots of suds. In the United States last year we spent more than $3.1 billion on hand and body soap.

That's a lot of soap, and a lot of money for soap. Or, rather, what we refer to as soap. You may be surprised to learn that a lot of the choices lining the soap aisles are not even soap. Check your label; if the word soap does not appear anywhere, then what you're washing with is technically a "synthetic detergent." (Betcha didn't know that.) From a quick look at Rite Aide's "soap" stocks, there was a good mix of both soaps ("hand soap," "deodorant soap") and detergents ("moisturizing cream," "beauty bar," hand wash"), in both liquid and bar form, with detergents seemingly better represented. (Read more here.)

The battle between bars and bottles

But while I suspect few soap-buying consumers are consciously deciding on a soap or a detergent, they are deliberately choosing form -- bar versus liquid.

Last year Americans spent more money on liquid soap ($sub req'ed), both hand and body ($2.7 billion), than on bar soap ($1.5 billion). But for most Americans it's not an either-or proposition; they tend to buy both liquid and bar soap. For example, as the market research firm Mintel put it in its April 2012 report ($sub req'ed): "More than seven in 10 use bar soap, but nearly seven in 10 use body wash [i.e., liquid soap for the shower]."

How did liquid soap become so popular? To help answer that question, let's start at the beginning.

The birth of soap

Soap has been around a long time. Longer than you might think. At least as far back as 2800 B.C., the date assigned to a clay pot containing a soap-like substance, which was found in an archaeological dig of an ancient Babylonian site.

The first known writings about soap are generally credited to 2nd century A.D. Greek/Roman philosopher/physician Galen who advised that it was not only handy for getting clean but also for warding off sickness. Imagine, not only the birth of soap but the birth of modern preventative medicine.

Soap from saponification

According to the Oxford English Dictionary, soap, a "word widely represented in the European languages," comes to us from the Old English sāpe ("of West Germanic origin"). Other sources trace its root to the Latin word for soap, sapo. But the Encyclopedia Britannica has it that the Romans learned of soap from ancient Mediterranean peoples or the Celts, whose name for soap was saipo, from which the English word soap is thought to be derived.

Regardless of how it got its name, it turns out that the production of soap (which is technically a salt) involves a chemical process called saponification (or neutralization) whereby an alkali (lye) is used to hydrolyze (or add water molecules to) animal and/or vegetable fats and oils. (Because many a soap is made from animal products, it can have a significant carbon footprint -- more on that later.).

The end result of the saponification process is what's called neat soap -- a combination of soap and water as well as glycerin. To get it to the form we recognize it as, drying turns the neat soap into pellets, which are then mixed with fragrances and colors, then refined and finally extruded and cut into bars, the stuff that many of my generation still prefer.

Liquid soap arrives on the scene

Now, as we all know these days, soap doesn't have to be solid. We owe that fact to a gentleman named William Shepphard, who patented liquid soap that had "a consistency of molasses" in 1865. But for more than a century his patent largely remained on the shelf when it came to hand and body soap. All that changed in 1980 when Minnetonka Corporation introduced Softsoap to American consumers. And so began the battle between bar and liquid, a fight that still rages on.

Turns out, though, that even though Softsoap's parent company "cornered the market" on the liquid stuff, it has taken decades and lots of marketing to make body washes and liquid soaps competitive with bars. According to a May 2000 report [pdf] by the University of Missouri's Center for Competitive Analysis, in 1998, 18 years after the introduction of Softsoap, "bar soap sales [still] accounted for 62.7% of dollar sales for bath and hand soaps."

But the trend has been upward since then and liquid soaps are fast becoming the soap of choice, according to Mintel, among young and affluent Americans.

Okay, we're a nation enamored of liquid soap. But is that a sensible choice? Let's take a look.

Liquid soap not on solid environmental ground

The consensus on the relative merits of bar versus liquid soap from an environmental point of view is clear -- liquids are the losers. (See here and here.) And since research [pdf] has found that "40% of female skin care shoppers describe themselves as 'ecologists,' implying that environmental considerations are also becoming more important," soap's green scorecard is important to a lot of washers. So here are some interesting considerations.

In a cradle-to-grave life-cycle analysis of household cleaning agents, including personal body cleansers, Annette Koehler and Caroline Wildbolz of the Swiss Federal Institute of Technology in Zurich found that for a per application or per wash basis, the carbon footprint of liquids is about 25 percent larger than that of bar soaps.

Why? In large part because for a typical visit to the sink, we use almost 7 times more liquid soap (2.3 grams) than bar soap (0.35 grams). That extra soap means more chemical feedstocks and more processing, and thus more energy and carbon emissions.

Liquids also require more energy for packaging production and disposal.

These disadvantages from liquid soaps are offset somewhat by the fact that we tend to use about 30 percent more heated water washing with bar soap than with liquid. (Betcha didn't know that either.)

Liquid soap sending dollars down the drain

If liquid soap is a bad bet for the environment, why are so many embracing it? Market research points to convenience and successful marketing (such as the Old Spice ads that went viral) as two primary factors.

Successful marketing indeed; so successful in fact that it has induced consumers to spend more money on something we don't need. Consider the following:

During a recent price check at my local grocery store, I found that a typical 177-milliliter plastic (!!) bottle of liquid soap went for $2.69, while a 12-ounce three-bar pack of solid soap was $3.99. Those numbers translate into about 1.2 cents per gram of bar soap and 1.5 cents per gram of liquid soap. In other words, bar soap is the better bargain.

But it's a lot worse than that because we use significantly more soap when it's in liquid form as opposed to solid (see above). I estimate that washing up with bar soap will cost you 0.4 cents -- less than half a penny -- per wash while scrubbing with liquid soap will set you back 10 times as much or about 3.5 cents per wash.

The bottom line: not only is liquid soap a bad environmental bet, it's a bad bet for your family budget.

Grime and germs and all that

Now, I don't mean to get into a lather about this, but consider the possibility that we've been sold a bill of soapy goods by the soap marketing mavens.

On the issue of convenience: Okay, bar soap can be a drag because it can get gross and slimy when it sits in a puddle of water. But that's what soap dishes with appropriate drainage are for.

And then there's the whole hygiene thing: Some, including the Centers for Disease Control and Prevention, recommend liquid soap because bacteria from one person can accumulate on a bar of soap and spread to someone else. But these recommendations are for sterile conditions in dental clinics. Should they apply to our homes?

Consider: We wash with soap to remove the bacteria on our hands; shouldn't that very same washing do just as well with any bacteria that might be on the soap? There are scientific studies that suggest that it does. For example, this 1998
published in the journal
Epidemiology and Infection
and conducted by Dial (a purveyor of both bar and liquid soap) concluded that "little hazard exists in routine handwashing with previously used soap bars." In this study 16 subjects washed their hands with bars of soap that had been laced with bacteria. After washing, the investigators were unable to find detectable levels of bacteria on the subjects' skin.

At a time of peril for our environment and economic hardship for so many, perhaps we should all consider washing our hands of washing with liquid soap.


Read more articles in our Chemical Marketplace series

Correction: December 4, 2013
The post has been corrected for the amounts of liquid and bar soaps used for a typical washing at the sink. All subsequent calculations have been corrected as well.

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