Transparent liquid soap becoming opaque at low temperature

[Hoang Duong]

I made a transparent liquid soap sample from fatty acid. My sample is transparent at room temperature. But when I store my sample at low temperature about 20C, it's white and opaque instead od transparent. What happened? Is it still good to use?

 

[Hoang Duong]

I used about 14% fatty acid (lauric, myristic, palmitic and amount of very very small stearic acid), I added some of surfactant such as CDE, CAB, polysorbate 20 and decyl glucoside (about 10%).

 

[ResolvableOwl]

Welcome to SMF, @Hoang Duong !

You seem to already have some experience with formulating liquid soaps. If you don't mind, feel free to introduce yourself, your knowledge, and your motivation in the introduction forum!

To your specific question: I guess you have neutralised the FFAs with KOH to make up the respective potassium salts?

Soaps from long-chain fatty acids (palmitic, stearic) have a very temperature-dependent solubility. It's the reason why Hot Process and rebatching works for bar soap (liquid-ish at high temperature, solidifying upon cooling).
In liquid soap, you either have to live with/work with/embrace an opaque look, or avoid long-chain saturated FAs (e. g. use oleic instead of palmitic/stearic acid). Mid-chain saturated soaps (lauric/myristic) don't precipitate, but the soaps can feel harsh and “stripping” to the skin in an uncomfortable way.

When a hot, clear potassium stearate/palmitate solution cools down, the soaps arrange into tiny crystals that precipitate out of solution, and often shimmer like mother-of-pearl, which can be a quite attractive appearance.
It's still soap, this is a purely physical process and does in no way interfere with the performance of the soap. It might be a cosmetic issue if the tiny crystals settle to the bottom and the soap appears to “tip over”. Unfortunately this is a slow process that is difficult to forecast, and depends on many things like storage temperature, concentration/dilution, and viscosity.

Is there a reason why you use free fatty acids, and not create your own FA profile via saponification of oils/fats?

https://www.soapmakingforum.com/threads/what-to-expect-from-various-oils-in-ls.62864/

 

[Zany_in_CO]

I added some of surfactant such as CDE, CAB, polysorbate 20 and decyl glucoside (about 10%).

Good advice from @ResolvableOwl!
I can't help you. We don't use those ingredients to make lye-based liquid soap. You are in the lye-based liquid soap forum. You will get more responses if you start a new thread in the Bath and Body Forum.

 

[Hoang Duong]

Good advice from @ResolvableOwl!
I can't help you. We don't use those ingredients to make lye-based liquid soap. You are in the lye-based liquid soap forum. You will get more responses if you start a new thread in the Bath and Body Forum.

Thanks for your advice. I will pay more attention to this

 

[Hoang Duong]

Welcome to SMF, @Hoang Duong !

You seem to already have some experience with formulating liquid soaps. If you don't mind, feel free to introduce yourself, your knowledge, and your motivation in the introduction forum!

To your specific question: I guess you have neutralised the FFAs with KOH to make up the respective potassium salts?

Soaps from long-chain fatty acids (palmitic, stearic) have a very temperature-dependent solubility. It's the reason why Hot Process and rebatching works for bar soap (liquid-ish at high temperature, solidifying upon cooling).
In liquid soap, you either have to live with/work with/embrace an opaque look, or avoid long-chain saturated FAs (e. g. use oleic instead of palmitic/stearic acid). Mid-chain saturated soaps (lauric/myristic) don't precipitate, but the soaps can feel harsh and “stripping” to the skin in an uncomfortable way.

When a hot, clear potassium stearate/palmitate solution cools down, the soaps arrange into tiny crystals that precipitate out of solution, and often shimmer like mother-of-pearl, which can be a quite attractive appearance.
It's still soap, this is a purely physical process and does in no way interfere with the performance of the soap. It might be a cosmetic issue if the tiny crystals settle to the bottom and the soap appears to “tip over”. Unfortunately this is a slow process that is difficult to forecast, and depends on many things like storage temperature, concentration/dilution, and viscosity.

Is there a reason why you use free fatty acids, and not create your own FA profile via saponification of oils/fats?

https://www.soapmakingforum.com/threads/what-to-expect-from-various-oils-in-ls.62864/

Thanks for your explanation. I used KOH to neutralize fatty acids in the liquid soap system. The reason I used these fatty acids to make the liquid soap is I want to compare the product's effectiveness made from different ingredients.

 

[Susie]

Thanks for your explanation. I used KOH to neutralize fatty acids in the liquid soap system. The reason I used these fatty acids to make the liquid soap is I want to compare the product's effectiveness made from different ingredients.

Most true soap based liquid soaps will turn cloudy in low temperatures, but will return to clarity when they warm up. Nothing to worry about.