Muggles wrote in news
lvudp$cvf$1
@wxy247t1uve70-5cv.eternal-september.org:
On 8/3/2017 12:29 PM, Doug Miller wrote:
Muggles wrote in newslvhi0$iam$1
@wxy247t1uve70-5cv.eternal-september.org:
I know there's some sort of process going on when soap foams and bubbles
up whether or not it's bath soap or dish soap, and I always thought the
foam in the soap is what broke down the dirt and oils.
Nope. It's the soap in the water that breaks down oils and helps dissolve or suspend dirt.
http://www.explainthatstuff.com/detergents.html
Foam forms when soapy water is agitated because the surface tension of soapy water is
much lower than that of pure water, that's all.
If it were the foam doing the cleaning, how would a clothes washer ever get your clothing
clean? The foam is all on top of the water, and the clothing is under the water.
OK Thanks for the link!
The one thing I haven't seen a specific answer to is why does bath oil
prevent soap from foaming up?
A soap bubble is a layer of water a few molecules thick, sandwiched between two layers of
soap molecules (or the other way around, I misremember which) -- the key is that this is
enabled by the lowered surface tension of the water that comes from dissolving soap in it.
Dissolving oil into the soap as well disrupts this process, and a bubble won't form.
For example, when I put the liquid bath soap onto a bath puff, it
usually will foam up when I add water to it.
If add some bath oil to the water first, and then try to use water with
bath oil in it to foam up the soap filled bath puff, it's like the bath
soap doesn't do anything - doesn't foam up,
OK so far...
and is useless to wash with.
It's *less* useful, but that's not synonymous with useless.
I understand what has been mentioned thus far in the explanations about
the molecules and emulsions.
Does oil prevent soap from foaming up because the reaction between the
two is instantaneous and soap becomes an emulsion on contact with oil,
therefore, no longer actually being soap?
Almost right. The soap permits the water and oil to form an emulsion. And that's why soap
works to get things clean: it turns something that won't mix with water into something that will.