chemistry 101 for salt to thicken liquid soap

[Feather]

Does anyone have the chemistry for what salt does to liquid soap when used for thickening?
Does it affect the grease cutting power?
Does it change the PH?
I have a little background in chemistry and organic chemistry, but, I don't have this. Thank you in advance. ~Feather

 

[lsg]

http://swiftcraftymonkey.blogspot.com/search?q=salt

Scroll down to the heading "Surfactants: Building viscosity - increasing surfactant concentration"

 

[DeeAnna]

"...what salt does to liquid soap when used for thickening?..."

Salt has the ability to alter the chemical structure of a liquid soap. The LS can go from a true solution (individual molecules or very, very small groups of molecules of one material dissolved in another) to a colloid (larger particles/droplets of one material suspended in another) and back again, depending on the salt concentration. A solution is thinner. A colloid is thicker.

Colloid chemistry is the reason why bar soap forms gloppy "snot" when it is dissolved in water to form a liquid. People often think they're going to make this amazing discovery that sodium soap can indeed be used to make a nice liquid soap. Sodium soap is less soluble in water than potassium soap, so rather than go into solution with the water, the sodium soap is even more likely than a potassium salt to form a colloid -- and one with a nasty gloppy consistency.

Colloid chemistry is not covered much in standard chem classes, so don't feel too bad about not knowing much about it. I'm still learning too.

 

[juliet]

Thanks! I've been wondering about that myself.

Funny how it seems to work better with some soaps than others. A pure castile thickens up very quickly with not much salt solution but I cannot get my 100% coconut to thicken up no matter how much salt solution I add, or how much salt I add to the dilution water.

 

[Feather]

Thanks! I've been wondering about that myself.

Funny how it seems to work better with some soaps than others. A pure castile thickens up very quickly with not much salt solution but I cannot get my 100% coconut to thicken up no matter how much salt solution I add, or how much salt I add to the dilution water.

well, I'm no expert but I have done a bit of reading here.
Have you read about 'salt bars', where you take a high coconut oil CP soap (because it is better at cleaning but very drying) and add 75%-125% salt by weights? Supposedly this type of soap will have some lather/creaminess even with the addition of the salt. The salt has a healing effect, akin to bathing in the ocean salt water. Good for many skin conditions.

So there is a jump in my logic here that says, coconut soap, whether cold processed or liquid soap, will not be affected as much (it will still lather) than something made with mostly another type of oil.

1. I haven't seen another type of oil that acts this way--though, I would love to see other oils with this property in soap.
2. I believe but have not tried to thicken coconut oil soap with salt but it would seem to be that the answer to that is "a lot of salt" and that the lathering/creaminess properties would suffer at the same time it begins to thicken the soap.

Now I'm sure there is someone more qualified to give you an answer than myself. Someone will come along soon and educate us all on this. I hope.

 

[juliet]

Interesting, I hadn't thought of the link with salt bars. Palm kernel oil is very similar in fatty acid profile to coconut but it behaves very differently in liquid soap. I make a coconut/palm kernel castor and olive and the pk one dilutes at 1:1.6 and thickens nicely with a little salt (half tsp to 250 ml) whereas the coconut one dilutes at 1:1.2 and needs about double the salt to thicken. I should do an experiment with a 100% pk and try thicken that.

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