Just a quick theory about why upside down loading, and also face lathering, are so effective...
You've probably all heard the upside down loading method discussed by Mantic59. He discusses the importance of water being in the breech of the brush.
I also read that generating lather needs friction (see below.)
Combining these, my theory is that in the breech, bristles are fixed closer together than at the tips. As you move the brush there is friction between bristles generating bubbles. But in the breech, the tightly packed bristles, and their shorter movements mean the bubbles are small, generating rich lather. At the tips, you're more likely to get big bubbles - suds.
Face lathering not only has the brush sideways or bristles up, you also force the mixture into the breech if you splay the brush. Hence creamy lather is made in the breech.
I know the quote below isn't fully scientific, but it's the best I found searching "how is lather made". Maybe "friction" shouldn't be taken literally.
But do you think my theory holds water?
(Pun intended!)
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Quote from What Makes Soap Lather - Soap Startup - https://soapstartup.com/what-makes-soap-lather/
"Upon mixing water and soap, thin sheets are created where a thin layer of water molecules is put in between two layers of soap molecules. As mentioned before, the hydrophilic and hydrophobic ends are placed accordingly in this position, with the hydrophilic ends pointed toward the water and the hydrophobic ends pointed toward the oil or dirt.
Lather Needs Friction
In order to create the lather, friction also must occur. By rubbing a bar of soap over wet skin or a cloth, this is the friction that is needed, which is also creating tiny air bubbles on the surface of the soap.
Because hydrophobic ends are water repelling, they attach themselves to the air bubbles during this process. Then, this creates a thin film with enclosed air that is trapped in between. This enclosed air is commonly called a soap bubble."
You've probably all heard the upside down loading method discussed by Mantic59. He discusses the importance of water being in the breech of the brush.
I also read that generating lather needs friction (see below.)
Combining these, my theory is that in the breech, bristles are fixed closer together than at the tips. As you move the brush there is friction between bristles generating bubbles. But in the breech, the tightly packed bristles, and their shorter movements mean the bubbles are small, generating rich lather. At the tips, you're more likely to get big bubbles - suds.
Face lathering not only has the brush sideways or bristles up, you also force the mixture into the breech if you splay the brush. Hence creamy lather is made in the breech.
I know the quote below isn't fully scientific, but it's the best I found searching "how is lather made". Maybe "friction" shouldn't be taken literally.
But do you think my theory holds water?
(Pun intended!)
------------------
Quote from What Makes Soap Lather - Soap Startup - https://soapstartup.com/what-makes-soap-lather/
"Upon mixing water and soap, thin sheets are created where a thin layer of water molecules is put in between two layers of soap molecules. As mentioned before, the hydrophilic and hydrophobic ends are placed accordingly in this position, with the hydrophilic ends pointed toward the water and the hydrophobic ends pointed toward the oil or dirt.
Lather Needs Friction
In order to create the lather, friction also must occur. By rubbing a bar of soap over wet skin or a cloth, this is the friction that is needed, which is also creating tiny air bubbles on the surface of the soap.
Because hydrophobic ends are water repelling, they attach themselves to the air bubbles during this process. Then, this creates a thin film with enclosed air that is trapped in between. This enclosed air is commonly called a soap bubble."
