# How Does Soap Clean Hands?



## jessicaneger78 (Aug 9, 2012)

Soap is a very useful substance that allows us to more effectively clean our hands. To understand how soap cleans our hands, you must first understand the chemistry behind water, dirt and grease. Water is a polar molecule. This means that water molecules (hydrogen and 2 oxygen) tend to separate into positive and negative ends. Now some substances, such as dirt and salt, are water soluble. This means they are able to easily dissolve in water, because their molecules have either positively or negatively charged parts (ions) that are attracted to the charges of the polar water molecules (they are hydrophilic). This allows them to become separated in the water and dissolve. Other substances, such as grease and oil, are not water soluble. This means they are not able to dissolve in water because their molecules do not contain positive and negative parts (ions), and so they are not attracted to the water molecules (they are hydrophobic). This means they do not become separated when they come in contact with water, and so they are not able to dissolve in water.

Chemistry of Soap

Soap is able to solve the problem of grease and oil's not being water soluble. This is because of the chemical composition of soap. Soap has an ionic head and a non-polar tail. This means that the head of a soap molecule is attracted to water, and the tail is attracted to oil and grease. So when soap comes in contact with an oil, it connects the oil to the water and allows it to be washed off. Other water-soluble dirt on your hands can be washed off with only water, as mentioned above. Also, soap is able to decrease water's high surface tension, which is caused by the many hydrogen bonds that hold water together. When soap is used, water's surface tension is reduced; therefore, the water is able to spread out more, because it is not being held together as tightly by the hydrogen bonds. This allows the water to more effectively dissolve the dirt and oil on your hands.


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## denniswoody (Dec 11, 2011)

I'm not sure what prompted this post but it was very informative. Thanks! How about a follow-up on soap and germs/bacteria. Question, if I handle chicken do I need soap or is water enough to clean my hands?


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## Knothead47 (Feb 10, 2010)

Interesting.


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## Multiwood (Feb 24, 2013)

Yes that is interesting. All I know is it works.


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## OPG3 (Jan 9, 2011)

Jessica(?) Welcome to the Router Forums!

Very informative! Thanks for sharing. Now, I have a serious question...My house is on a septic tank. Tubs, sinks, toilets and showers all go to the septic tank - which is typical in my area, except for cases where a sanitary sewer system is in use. The "items" in the septic tank are referred to as effluent (liquid) and solids. Bacteria break-down these "items" until they enter the drain field where they go into the soil. Eventually this becomes ground water.
Question: When SOAP is designated as ANTI-BACTERIAL, how does that affect the septic system? Am I killing the very bacteria that my system depends on?

Otis Guillebeau from Auburn, Georgia


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## zm15 (Dec 16, 2013)

Super interesting! Now, how exactly does the wonderful Orange Goop work so well?


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## papasombre (Sep 22, 2011)

Hi, Jessica.

Welcome to the forum.

Very interesting topic. Besides the hygiene I use the leftover pieces of soap to lubricate the screws when I am doing woodworking


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## Jerry Bowen (Jun 25, 2011)

Johnny wonders why it worked so well for cleaning profanity from his mouth when his mother used it when he was a little boy.


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## Bricknhank (Dec 28, 2013)

jessicaneger78 said:


> Soap is a very useful substance that allows us to more effectively clean our hands. To understand how soap cleans our hands, you must first understand the chemistry behind water, dirt and grease. Water is a polar molecule. This means that water molecules (hydrogen and 2 oxygen) tend to separate into positive and negative ends. Now some substances, such as dirt and salt, are water soluble. This means they are able to easily dissolve in water, because their molecules have either positively or negatively charged parts (ions) that are attracted to the charges of the polar water molecules (they are hydrophilic). This allows them to become separated in the water and dissolve. Other substances, such as grease and oil, are not water soluble. This means they are not able to dissolve in water because their molecules do not contain positive and negative parts (ions), and so they are not attracted to the water molecules (they are hydrophobic). This means they do not become separated when they come in contact with water, and so they are not able to dissolve in water.
> 
> Chemistry of Soap
> 
> Soap is able to solve the problem of grease and oil's not being water soluble. This is because of the chemical composition of soap. Soap has an ionic head and a non-polar tail. This means that the head of a soap molecule is attracted to water, and the tail is attracted to oil and grease. So when soap comes in contact with an oil, it connects the oil to the water and allows it to be washed off. Other water-soluble dirt on your hands can be washed off with only water, as mentioned above. Also, soap is able to decrease water's high surface tension, which is caused by the many hydrogen bonds that hold water together. When soap is used, water's surface tension is reduced; therefore, the water is able to spread out more, because it is not being held together as tightly by the hydrogen bonds. This allows the water to more effectively dissolve the dirt and oil on your hands.


Hmmm. I'll bet my mom never used this analysis when she used to use soap to wash my mouth out when I was a kid!:lol:


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## elfridaauston87 (Jul 1, 2019)

Interesting post.


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## chessnut2 (Sep 15, 2011)

Very interesting. Thanks!


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## roxanne562001 (Feb 5, 2012)

Welcome to the forum Jessica. I never thought of soap that way


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## CharleyL (Feb 28, 2009)

This is a post that originated in 2013. I doubt that the originator even frequents this website any more. An interesting post though. 

When working in the printing industry, I found that using waterless hand cleaner was a great way to get printer's ink, oil, and grease stains out of my work clothes as well as my hands. A little bit worked into the stained areas before throwing the clothing into the wash, removed the offending material, usually in just one washing. Oil and water don't normally mix, but waterless hand cleaner is a water soluable kind of oil and it will mix with the ink and grease easily, then it will mix with the water, assisted by the laundry detergent. The result usually completely removes the stain in one washing, but stubborn stains might require a repeat of the process. Sweat stains also come out easily with this process. I frequently wear baseball type caps and my engineers caps when driving the train in my avatar, and when they get sweat stained and dirty I add a little waterless hand cleaner and a scrub brush to work it into the stained areas before washing them. I end up with nice clean hats this way. Nothing else that I've tried on sweat stains has ever worked this good. 

Charley


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## DesertRatTom (Jul 3, 2012)

Welcome Jessica. Interesting post. My understanding is that soap simply makes it hard for bacteria to stay attached to the surface of skin, so particles of all types are rinsed away.

On septic systems: _A septic system only functions effectively only when it maintains the right balance of beneficial bacteria. This bacteria helps to break down solid waste, and prevents your septic system from backing up.

When you introduce certain chemicals into your septic system, the growth of good bacteria can be slowed, or the bacteria may even be completely eliminated. Less bacteria in your septic tanks means more odor, a slower system, more frequent pump outs, or even a costly and inconvenient repair.

Antibacterial soap is made to kill bacteria. This is great for cleaning, but terrible for your septic system. A septic system requires two types of bacteria to do its job: anaerobic bacteria, which doesn't require oxygen, and aerobic bacteria, which does require oxygen. Inside your septic tank, anaerobic bacteria is needed to break down solid waste, while aerobic bacteria in your system's leach field destroys harmful pathogens which can cause disease. Antibacterial soaps kills both types of bacteria.

Almost every homeowner uses antibacterial products. Besides antibacterial hand soap, septic system damaging antibacterial products include:

tile, sink, shower and tub cleaners;
toilet bowl cleaners;
laundry detergents;
drain cleaners;
counter-top cleaners, and
commercial and industrial cleaners.

Does this mean I have to sacrifice cleanliness to keep my septic system running?

No. In fact, the value of using antibacterial soap is highly disputed. The FDA states that antibacterial soap is not shown to be better at protecting against disease or infections than correctly washing with normal soap and hot water. In addition, there are multiple studies which conclude that the use of antibacterial soap may actually decrease the ability of user's immune system to fight off sickness, and may not be safe for long-term use. --https://www.septicsafe.com/blog/the-dangers-of-antibacterial-soap-in-a-septic-tank/_

I have started using Dawn for hand and dish washing. This is what they use on animals after an oil spill. Since all soap makes skin too slippery for germs to get a grip it's basically as effective as the antibacterial stuff. Rinses off easily and doesn't kill bacteria in the septic system, gentle on skin...what's not to like?

We had "risers" installed for quick and easy access to the settling tanks, covered by artifical rocks. We get a discount on having it pumped since they don't have to dig. The real problem is with the paper products., which is why we pump regularly despite low flush toilets. Paper that gets into the deep tank will clog and fill it in fast.


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## Biagio (Mar 2, 2013)

@CharleyL, should you run out of waterless hand cleaner, a few drops of dishwashing liquid and a pinch or two of baking soda do a marvelous job of removing grease, paint and varnish from hands. Better than some of the commercial hand cleaners, which somehow do not get into fingerprint ridges, nail folds and hair follicles. Very light brush with a. Soft brush, and you will not believe the results. Don’t know about on clothing - have not tried.

@DRT, the FDA made the point, although the soap companies are still rabbiting on about killing 99% of germs. What some of the “antibacterial soaps” do, is to affect skin pH, etc, and lead to dry skin, or worse, dry eyes - there seems to be an epidemic of the latter. Then they try to counteract by adding oils, “moisturizers”, etc. I have never understood why one would want to wash to clean off oils and dirt, and in the process make things oily again. But I suppose several billion women can’t be wrong.


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## DesertRatTom (Jul 3, 2012)

Biagio said:


> @CharleyL, ...But I suppose several billion women can’t be wrong.


Oh no, it's always the man who's wrong. Just ask my wife. :wink:


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## DaninVan (Jan 1, 2012)

Any wife, Tom; any wife. 
And on the remote chance that you are right, do _not _say "See, I told you so." Unless of course you enjoy sleeping under the stars.


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## Cherryville Chuck (Sep 28, 2010)

DesertRatTom said:


> Welcome Jessica. Interesting post. My understanding is that soap simply makes it hard for bacteria to stay attached to the surface of skin, so particles of all types are rinsed away.


The original post was correct. Soap is a somewhat long molecule that is water soluble on one end and oil soluble on the other end. Therefore able to dissolve in both.



> On septic systems: A septic system only functions effectively only when it maintains the right balance of beneficial bacteria. This bacteria helps to break down solid waste, and prevents your septic system from backing up.
> 
> When you introduce certain chemicals into your septic system, the growth of good bacteria can be slowed, or the bacteria may even be completely eliminated. Less bacteria in your septic tanks means more odor, a slower system, more frequent pump outs, or even a costly and inconvenient repair.


True. For that reason I have a drain pit that my washing machine drains into that is separate from my septic tank. The chemicals from the washer are terrible for the septic tank, particularly chlorine bleach, so I only have my toilet, tub, and bathroom sink draining into it. Grey water with plain regular soap isn't that harmful to it. I haven't touched my septic system in the 35 years since I set it up.



> Antibacterial soap is made to kill bacteria. This is great for cleaning, but terrible for your septic system. A septic system requires two types of bacteria to do its job: anaerobic bacteria, which doesn't require oxygen, and aerobic bacteria, which does require oxygen. Inside your septic tank, anaerobic bacteria is needed to break down solid waste, while aerobic bacteria in your system's leach field destroys harmful pathogens which can cause disease. Antibacterial soaps kills both types of bacteria.
> 
> Almost every homeowner uses antibacterial products. Besides antibacterial hand soap, septic system damaging antibacterial products include:
> 
> ...


If you remember back about 25 to 30 years ago Phisohex was very popular. Then they discovered that regular use of it was harmful. It had side effects in some people such as skin irritation. Other possible side effects were suggested coupled with studies that showed anti bacterial soaps were no more effective at cleaning your hands: https://www.webmd.com/cold-and-flu/news/20070817/plain-soap-as-good-as-antibacterial#1 Soap doesn't make your skin too slippery for germs to stick to, it dissolves the oil that they stick to. That coupled with friction of rubbing your hands together breaks them loose so that water can rinse them away. https://www.todayifoundout.com/inde...ll-bacteria-can-really-effective-getting-rid/


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