Thursday, 15 January 2015

Ingredient class: What's the Difference Between Sodium Hydroxide andPotassium Hydroxide in soap making?

Ever since I started soap lab, I'm asked this question several times a day.

 So what is the difference between NaOH vs KOH? 
To those of you who learned chemistry, remember the periodic table? The first column with all the one positively charged metal? Well that's where these two chemical fits in. It's in a form of hydroxide because it had reacted with the hydroxide ion, resulting in sodium or potassium hydroxide. Comparatively the molecules of potassium is larger and heavier than sodium, therefore the bonds for potassium is weaker as compared to sodium. 
So what has all this got to do with soap you ask
Well simple, let's go back to soap making centuries ago. To make basic soap, u need fats ( at that point of time they use tallow or lard) reacted with lye solution (a process called saponification) resulting in crude/raw soap and glycerol. This lye/sodium hydroxide/potassium hydroxide needs to be mixed with water before mixing with the fats or it wouldn't have a reaction. When mixing with water, these hydroxide will generate heat (ectothermic reaction) so be careful and wear your safety gears when handling them. 
So does that mean you can use either potassium or sodium hydroxide for making soap? 
Yes and no. Well remember previously I said about the bonds? Well sodium hydroxide will react with the oils, causing the molecules to be denser and tighter as compared to potassium hydroxide, therefore, it's more suitable for solid soap. Potassium hydroxide on the other hand is more soluble in water so it's more suitable for liquid soap. 
Can I use either one for another?
I've never tried it before but theoretically, potassium hydroxide will not solidify the soap as compared to sodium hydroxide. As for sodium hydroxide for liquid soap, yes you can make liquid soap this way, however, it's really difficult to dilute the sodium hydroxide soap paste. Even after that, you will get clumpy liquid soap. Also, because the molecules are so close to each other, it's really hard to get a transparent liquid soap with this. Let me know if anyone tried it and what's the results:) 
I hope I have clarified things for most of you. Let me know what are your thought:) 
Till then have a great day!

Malay version:

Apakah Beza KOH dgn NaOH?
Koh lebih di gunakan untuk membuat liquid soap, dan NaOH di gunakan untuk membuat sabun buku.

Disebabkan Oleh molekul kedua dua chemical ini, KOH adalah lebih soluble terhadap air berbandingkan dengan NaOH. Oleh iTu, Nak keraskan KOH ni lebih susah. NaOH ni pulak, sebab molekul dia sangat rapat, lebih baik untuk digunakan untuk membuat sabun buku.

Bolehkah saya menggunakan NaOH untuk membuat liquid soap?
Secara theory mmg boleh. Tetapi, disebabkan molekulnya yang rapat antar a satu sama lain, quite susah untuk dilute soap paste yang dibuat daripada sodium hydroxide. Dan kalau nak buat transparent liquid soap Lagi susah dengan NaOH ni. Tapi boleh try la kalau nak. Pas tu bagitau kita org yea kalau ada respi best:) 

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