Proper hand washing techniques say to wet your hands before applying soap, but I rarely see people doing that.
You have to pump about 5-7 times to get any amount of soap, then you get maybe 5 seconds of frigid ice cold water that you can hardly stand keeping your hands under, with no water pressure at all, then it stops. You either have to press a button again or wait for the sensor to detect you again, which of course takes a while. This goes on for some time. It encourages you to half ass or skip the hand washing procedure. Companies I guess think public health is less important than saving on the water bill.
1. Wet hands
2. Apply soap [ water stops ]
3. Lather well into crevasses
4. Rinse-off
If you are washing grease off your hands then you actually do want to apply the soap/washing up liquid first.
In this way the grease-loving end of the whatever-it-is molecules stick to the grease before the water-loving end gets to adhere to water. You can then remove the grease from your hands using less soap and with less water.
Also you should always silently sing the happy birthday song to yourself whilst washing your hands to make sure enough friction goes on for long enough to get the job done...
http://www.cdc.gov/handwashing/when-how-handwashing.html
World Health Organization:
http://www.who.int/gpsc/clean_hands_protection/en/
Mayo Clinic:
http://www.mayoclinic.org/hand-washing/art-20046253
WebMD:
http://www.webmd.com/cold-and-flu/cold-guide/cold-prevention...
American Red Cross:
http://www.redcross.org/prepare/location/school/flu-preventi...
I read that doing so minimises the risk of irritation, however, isn't that the same as locally diluting the soap? Is that the only reason?
"When is clean too clean" (or something like that) is the CDC document.
I've also heard that wet hands then soap makes for better coverage. I'd think that either way would work the same if peoe took enough time and effort with washing.
I would really like to know - with science - what the best method is. I suspect that at one point someone had to write a set of instructions and so that's what we've been doing ever since.
I'm no biology or chemistry expert so I might not have this completely right, but here's how I understand it.
Soaps are a surfactant, when you add water (dilute? You aren't pouring water on it, come on!) you "activate" the soap and that forms micelles. This is the "lather" reaction. This is good, we want this for cleaning.
http://health.howstuffworks.com/skin-care/cleansing/products...
>. So when you put soap in water, the ends of the soap molecules that are attracted to it latch on right away and the other ends stick straight up in the air. Any soap molecules trapped underneath will fight their way to the surface and eventually you end up with three layers: a layer of soap molecules, a layer of water and another layer of soap molecules pushing themselves away from the main body of water underneath. These three layers form the wall of a bubble .... The different ends of soap molecules are also what make soap so good at cleaning. As you learned earlier, when you mix soap with water, it lowers the surface tension of the water by separating the water molecules, as the soap molecules push up between them. Meanwhile, the other ends of the soap molecules that are attracted to dirt grab on to it. As multiple soap molecules attach themselves to the same piece of dirt, they eventually break it down into tiny particles, which then can easily be washed away
This is most noticed with bar soap, but I still say you can't form a proper lather with liquid soap without wetting your hands first, and it doesn't cover the entirety of your hands (backs, between the fingers) unless you use a TON and I mean a TON of soap.
Those are aimed at clinicians, who are unlikely to be covered in grease.