I’m told I wash my hands for too long but personally, it seems to me that to get my hands clean, the soap has to be on them for a period of time and perhaps that rubbing my hands together activates it or something but I can’t prove either explanation so I’m cur
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While some soaps do have an antibacterial aspect, most just make your hands slippery so the dirt “slides” off.
I’m sure you know, water and oil don’t mix together very well. That’s because oils are non-polar molecules and water is polar. Polar molecules stick to other polar molecules, and non-polar molecules stick to non-polar molecules.
Soap is what is called a surfactant. It’s a long molecule with one polar end and one non-polar end. This allows it to grab onto both a water molecule and an oil molecule, and allows the water flowing off your hand to wash away the oil too.
You don’t need to leave soap on your hands, but you do need to rub it all over your hands, in every crack and crevice, to ensure you’re washing everything off.
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As far as hand washing goes, the thing you need to remember is that you’re supposed to soap up while not in the water stream. Getting it all lathered up basically breaks up and lifts dirt and other undesirable things off your skin, so it can then be rinsed off. If you’re rubbing the soap in while also rinsing, you’re just washing the soap away before it can do this as effectively, wasting time and water.
So, rinse, apply soap, lather up (without running water over your hands), then rinse again.
The lye (sodium hydroxide) in soap is also caustic which allows it a certain solvent like property to cut through grease and dirt. And while some soaps do contain an antimicrobial agent, where you really get your bang for the buck in killing stuff is from the friction, like rubbing your hands together for 20 seconds or more.
There are (mostly) two types of molecules, polar and non-polar. Polar molecules like to stick to other polar molecules but do NOT like to stick to non-polar molecules. Water is a polar molecule, most things like dirt and grease are non-polar. So they don’t like to stick together. When you just rinse your hands with plain water you can get a good amount of the dirt and grease off with just the mechanical force of the water and rubbing your hands together. But there will be a thin layer of dirt and grease and ick left behind. Soap is one of those special molecules that is neither polar or non-polar. Instead it’s polar at one end, and non-polar at the other! So soap works by the non-polar end sticking to the molecules of dirt and grease, and the polar end sticking to the molecules of water, so when the water flows away it takes the soap and the connected dirt molecule away with it!
So yes the soap does need to be on your hands and rubbed in for it to work, because you need to expose all those dirt molecules to soap molecules so they can attach to each other and then attach to the water to get rinsed away. That’s why sometimes if your hands are really dirty or greasy you may need to wash multiple times, because the top layer gets bonded to the soap and then rinsed away but there’s still more beneath it that didn’t get exposed to the soap.
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