“Rub-a-dub-dub…” or how does soap clean? November 05 2014, 0 Comments


It’s taken me awhile to associate this nursery rhyme to my soap ramblings…it should have been an obvious choice. I’ve explained a lot of issues and facts around soap to date, but not the most obvious factor…how soap actually manages to work as a cleansing agent.

I’ve explained in the past how soap is made- refer Blogs: http://iloorganics.com/blogs/news/14658801-soap-making-methods and http://iloorganics.com/blogs/news/15089821-soap-its-all-in-the-making. Unfortunately, I’ve just discovered that our website host does not support archiving of our Blogs, and only displays a limited number of recent posts…so they can only be accessed via the above links. I’m looking into a way to get around this limitation.

So another chemistry lesson that I’ll simplify as best I can to explain the advantages of using soap for cleansing. Funny- I was at my doctor’s the other day and he pulled up an information link he’d posted on his Facebook page, and slung off at the complexity of the language used…like what did it mean? I’d read a couple of sentences and put it in the ‘too hard’ basket! I read once that if you can’t explain something clearly to your grandmother, then you’ve failed…and I fall into that age category, so I’ll see how it works in reverse.

Some simple facts: a salt mixes with and dissolves in water- an oil doesn’t mix with water. That’s the reason an alkali (a strong soluble salt of an alkali metal- NaOH/caustic soda) solution is used in the soap making process to begin with- it allows the oil to be combined with the lye (NaOH/water) solution to turn it into a solid soap salt…which then will in fact dissolve in water.

If we tried to wash oil off our skin or clothes with just water, the water wouldn’t penetrate the oil- there would be a natural molecular resistance by the water. Therefore, we need something that alters the surface tension of the water…a ‘surfactant’.

Water molecules tend to like each other and stay together. If you dropped some water on a flat surface, the molecules would tend to hold their form naturally and not spread out- they’d form more of a flattened, round drop as they huddled together. This characteristic structure of water molecules is called ‘micelles’.

If you watch rain falling on a window, the droplets tend to merge together and run down the glass in little runs aided by gravity- instead of wetting the glass uniformly. When we add a surfactant, it improves the ability of the water to wet things by changing the surface tension. If we’d applied a window cleaner/detergent to the glass prior to the rain hitting it, the rain would wet the window evenly instead of forming runs of droplets.

Soap molecules have a different characteristic structure. They have a head that likes water molecules- ‘hydrophilic’, and a tail that hates it- ‘hydrophobic’. When soap is added to water, the hydrophilic heads mix with the water, but the hydrophobic tails connect up with the oil molecules and push away from the water molecules. The oil molecules end up surrounded by water molecules in a circle and trapped- like a bit of an ‘encircle and capture the enemy’ scenario. This resultant molecular structure is then termed ‘micellas’- an emulsion of oil encapsulated in water that is then easily carried away with more clean water.

In summary, soap acts as a ‘surfactant’ and an ‘emulsifier’ to loosen oils and dirt from our skin. Similarly, it causes bacteria to loosen their grip on our skin- become trapped and be rinsed away. As much as people profess that soap is not required to cleanse the skin, it would take a lot of vigorous rubbing to effectively break the surface tension without soap…causing skin irritation. It’s recommended that hand washing with soap be done for 30 seconds, but the average person does it for less than 15 seconds.

Psychologically, we tend to associate the effectiveness of soap by the amount of bubbles/lather it produces. This is not the case at all. Even a low lathering soap like our ‘oli’ organic soap, made with organic extra virgin olive oil, is just as effective as our very popular dense lathering ‘coci’ organic soap, made with organic extra virgin coconut oil. The success of the process/chemistry isn’t increased by more lather. We’ve again been convinced of this being the case through commercial marketing- the more bubbles, the more cleaning power…wrong!

Do your hands and your body a favour and use our organic soaps to reduce the chemical burden on your skin…’oli’ being extremely mild for the constant exposure of hand washing.

Back to the nursery rhyme:
 Three men in a tub,
 And who do you think they were?
 The butcher, the baker,
 The candlestick-maker.
 They all sailed out to sea.
 ‘Twas enough to make a man stare.”

What on earth does this rhyme refer to? You’ve got to wonder about the various rhymes as statements of periods through history! Put into my world as part of a market community with the butcher…the baker…the candlestick-maker…I’m shuddering at the prospect! My soap shall have no part in the play!