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How Soap Works: The Science Behind Handwashing

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Re: How Soap Works: The Science Behind Handwashing

#61

Post by atombender »

nyanpasu64 wrote: post #52
NegativeLatency wrote: post #37

Earlier quoted context omitted.

It does just not very well. Maybe the pine sap is more interested in being stuck to pine sap than soap? There are things that are much better at cleaning non polar molecules off of surfaces, alcohols, gasoline, lye, brake cleaner etc, but they’re not great at cleaning your hands because they strip the lipids that make up your skin off.

Ironically I've found that lotion is better at cleaning resins/flux off my hands than soap alone.

Maybe for the same reason that you can remove greasy hair pomade (or other hard-to-wash-out hair products) from your hair by first applying a conditioner, then washing with shampoo. Supposedly the fats/oils in the conditioner bind to the grease and lets the soap get both.

Re: How Soap Works: The Science Behind Handwashing

#63

Post by mccrory »

Isthatablackgsd wrote: post #32
ProjectArcturis wrote: post #4

I understand soap molecules having polar and nonpolar ends, so that it can help nonpolar things dissolve in water. What I've never understood is, why doesn't soap clean off pine sap?

Pine sap are not water soluble, even with soap. Pine sap is resin based, resins need a different solvent that can dissolve it such as alcohol or mineral spirits. It the same for wax (THC/CBD) resins, they need alcohol to clean it off. It the same for blood stains on clothing. They are not generally water soluble, you could get them out if you put it under cold water if the stain is still fresh. Hydrogen Peroxide can…

If you use Hydrogen Peroxide, it will often also take some pigment with it from the clothing if that’s what your are getting the blood out from. So be careful not to inadvertently bleach something.

Re: How Soap Works: The Science Behind Handwashing

#64

Post by sgarrity »

I remember a science radio program from years ago (might have been https://www.cbc.ca/radio/quirks) summing up an explanation of how soap works with the summary: "Soap makes water wetter."

It's obviously an over-simplification for the purposes of education, but it works, as it has stuck with me.

Re: How Soap Works: The Science Behind Handwashing

#65

Post by okdood64 »

elhudy wrote: post #62

I was always under the impression that the purpose of soap isn’t to kill bacteria/viruses as the article implies, but to wash those thing off of your hands. Was my impression wrong?

Yes. If a pharmaceutical company's article (with better expertise in this area than the average HNer) isn't enough to convince someone here's an article from UNESCO:

https://www.unesco.org/en/articles/how-soap-kills-covid-19-h...

Re: How Soap Works: The Science Behind Handwashing

#66

Post by kube-system »

mvcalder wrote: post #15
ProjectArcturis wrote: post #4

I understand soap molecules having polar and nonpolar ends, so that it can help nonpolar things dissolve in water. What I've never understood is, why doesn't soap clean off pine sap?

If you, like me, often find yourself covered in pine sap. The product: Shout, for removing laundry stains will make quick work of removing sap from skin. Maybe the answer to your chemistry question is in there.

I looked up some SDS sheets, and it looks like there are multiple formulations with completely different ingredients.

Re: How Soap Works: The Science Behind Handwashing

#67

Post by lispisok »

When covid first hit I was smug because while everybody was freaking out buying up all the hand sanitizer and Clorox wipes I remembered the section college biochemistry about surfactants and bought a few extra bottles of soap. Sodium Laureth Sulfate et al. are super cool underrated substances imo

Re: How Soap Works: The Science Behind Handwashing

#68

Post by matheusmoreira »

jawns wrote: post #10

This is probably the stupidest question many of you will encounter today, but: If soap has an extraordinary ability to destroy viruses on our skin ... can eating soap give us some of those benefits for viruses that are already in our bodies? I'm not seriously envisioning chowing down on bar soap or using liquid hand soap as a salad dressing. But are there ways to use the _properties_ of soap that make it good for kil…

Your question is important. Sapophagia exists. People do this. It can give you gastrointestinal symptoms. Could be associated with nutritional deficiencies. Might kill you.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9881715/

https://pubmed.ncbi.nlm.nih.gov/30307335/

> The most common symptoms were

> labial oedema (28%, n = 153)

> oropharyngeal irritation (10%, n = 56)

> salivation (10%, n = 53)

> vomiting (9%, n = 48)

> cough (8%, n = 45)

> Among symptomatic patients (n = 276), one patient died from aspiration pneumonia and one patient died from a cardiogenic shock following oropharyngeal oedema, vomiting, cough and bronchial obstruction.

I'd also like to add: don't ever ingest anything containing methanol. That group may include hand sanitizers.

Re: How Soap Works: The Science Behind Handwashing

#69

Post by GauntletWizard »

okdood64 wrote: post #65
elhudy wrote: post #62

I was always under the impression that the purpose of soap isn’t to kill bacteria/viruses as the article implies, but to wash those thing off of your hands. Was my impression wrong?

Yes. If a pharmaceutical company's article (with better expertise in this area than the average HNer) isn't enough to convince someone here's an article from UNESCO: https://www.unesco.org/en/articles/how-soap-kills-covid-19-h...

Confusingly, the one graphic in that article shows the soap binding to dirt and viruses and washing them off and away. It does not show the tearing/destruction of the lipid shells, though the article also talks about it.

Re: How Soap Works: The Science Behind Handwashing

#70

Post by teach »

elhudy wrote: post #62

I was always under the impression that the purpose of soap isn’t to kill bacteria/viruses as the article implies, but to wash those thing off of your hands. Was my impression wrong?

I'm not an expert on this either, but I think it's true that IN GENERAL a lot of the value in soap is just "debulking". It does do that very well.

But in the specific case of COVID-19 soap happens to also destroy the virus particles and that turns out to be pretty valuable too. :)

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