why potassium hydroxide

Soapmaking Forum - Soap & Candle Forums

Help Support Soapmaking Forum - Soap & Candle Forums:

Spice

Supporting Member
Supporting Member
Joined
Mar 21, 2014
Messages
681
Reaction score
227
Location
NorCali
What is the difference between Lye and Pot Ash in liquid soap? Why cant lye be use?:confused:
 

The Efficacious Gentleman

Lifetime Supporter
Joined
Nov 19, 2013
Messages
9,055
Reaction score
9,295
Location
Austria
Potassium hydroxide and sodium hydroxide are made with two different metals - sodium and potassium.

As to why one makes a softer soap than the other, I can't tell you, but it might suffice to say that they are very different in many ways, for example the amount of KOH (potassium hydroxide) required to neutralize x grams of oil is different from the amount of NaOH (sodium hydroxide)

Pot ash, the result of water seeping through ashes, is often something else than both.
 

DeeAnna

Well-Known Member
Joined
Feb 20, 2013
Messages
13,563
Reaction score
19,689
Location
USA
All of the chemicals The Gent named are "lye" because they are all chemicals used to make soap. Unless the context is clear, you can't just say "lye" and have everyone understand the specific chemical you mean.

Sodium hydroxide lye makes solid (bar) soap. Potassium hydroxide lye and potash lye (potassium carbonate) both will make a paste or liquid soap. These are the three most common types of lye.
 

IrishLass

Staff member
Admin
Moderator
Joined
Feb 11, 2008
Messages
17,386
Reaction score
11,211
Location
Right here, silly!
Spice, forgive me, but I'm not sure I understand your question? KOH (Potassium Hydroxide) and NaOH (Sodium Hydroxide) are both commercially produced lyes: KOH is potassium-based lye and NaOH is sodium-based lye.

KOH (potassium-based lye) is what is generally used for making liquid soap, and NaOH is what is generally used for making hard/bar-type soap. So, as you can see, one can indeed make liquid soap from lye, as long as it is potassium lye (KOH)........ although it is possible to make liquid soap using both KOH and NaOH (I believe our Susie has made liquid soap using both lyes).

'Pot ash' is not exactly the same thing as commercially produced KOH. It's as the good Gent said- the result of water seeping through ashes.


IrishLass :)

Edited to add: DeeAnna beat me to it again! lol
 

Spice

Supporting Member
Supporting Member
Joined
Mar 21, 2014
Messages
681
Reaction score
227
Location
NorCali
Potassium hydroxide and sodium hydroxide are made with two different metals - sodium and potassium.

As to why one makes a softer soap than the other, I can't tell you, but it might suffice to say that they are very different in many ways, for example the amount of KOH (potassium hydroxide) required to neutralize x grams of oil is different from the amount of NaOH (sodium hydroxide)

Pot ash, the result of water seeping through ashes, is often something else than both.
All of the chemicals The Gent named are "lye" because they are all chemicals used to make soap. Unless the context is clear, you can't just say "lye" and have everyone understand the specific chemical you mean.

Sodium hydroxide lye makes solid (bar) soap. Potassium hydroxide lye and potash lye (potassium carbonate) both will make a paste or liquid soap. These are the three most common types of lye.
Spice, forgive me, but I'm not sure I understand your question? KOH (Potassium Hydroxide) and NaOH (Sodium Hydroxide) are both commercially produced lyes: KOH is potassium-based lye and NaOH is sodium-based lye.

KOH (potassium-based lye) is what is generally used for making liquid soap, and NaOH is what is generally used for making hard/bar-type soap. So, as you can see, one can indeed make liquid soap from lye, as long as it is potassium lye (KOH)........ although it is possible to make liquid soap using both KOH and NaOH (I believe our Susie has made liquid soap using both lyes).

'Pot ash' is not exactly the same thing as commercially produced KOH. It's as the good Gent said- the result of water seeping through ashes.


IrishLass :)

Edited to add: DeeAnna beat me to it again! lol
Thanks for the understanding, and sorry I wasnt clear. I can use the excuse that I wasnt clear either. I see that Pot ash is not what I thought it was. I thought that Pot Ash was KOH. Thanks IrishLass, for clearing that up. And I didnt even know that all are lyes, thanks DeeAnna. I will be making liquid soap, reading the "How to", I wasnt sure on the "why" for KOH. Thanks Gent because that gives me insight on the two. I will be using KOH for my liquid soap. I'm thinking too, that using Sodium Hydroxide would must likely take longer to soften the soap. Am I right on that thought?
 

DeeAnna

Well-Known Member
Joined
Feb 20, 2013
Messages
13,563
Reaction score
19,689
Location
USA
"...using Sodium Hydroxide would must likely take longer to soften the soap. Am I right on that thought?..."

I'm not really sure what you mean by "soften the soap" so I'll just say this -- Sodium hydroxide really won't work to make liquid soap. You really need to use KOH to make a proper liquid soap.
 

Spice

Supporting Member
Supporting Member
Joined
Mar 21, 2014
Messages
681
Reaction score
227
Location
NorCali
"...using Sodium Hydroxide would must likely take longer to soften the soap. Am I right on that thought?..."

I'm not really sure what you mean by "soften the soap" so I'll just say this -- Sodium hydroxide really won't work to make liquid soap. You really need to use KOH to make a proper liquid soap.
By soft I mean liquid. New to this.:)
 

Susie

Supporting Member
Joined
Aug 1, 2013
Messages
9,744
Reaction score
9,279
Location
Texas
NaOH (sodium hydroxide) makes bar soap. The structure of the molecules once saponification takes place is a rigid crystalline structure. (If I recall DeeAnna's explanation correctly.) Using NaOH to make soap that you then attempt to dilute to make liquid soap will result in a snotty consistency mess that does not function as soap. IN MY EXPERIENCE. Others have other results. But I have tried this over and over, and nothing but snotty non-soapy soap results.

KOH (potassium hydroxide), when saponified, has a looser structure. This yields a paste that can then be diluted for good liquid soap.

Some folks use dual lyes- KOH + NaOH to get supposedly thicker liquid soap. This has not been my experience. However, NaOH is a good bit cheaper for me to buy. So, if I am making some sort of household soap (dish or laundry), I will often use 20-30% NaOH to reduce the cost, without negatively affecting the cleansing power. It does reduce the lather, which is a good thing in a laundry soap.
 

Seawolfe

Well-Known Member
Joined
Jan 21, 2014
Messages
3,272
Reaction score
2,999
Location
So Cal
I remember when I was new and I had hopes that NaOH lye could be used to make liquid soap - and everyone on the internet (it seems) tells you to just dissolve a grated bar of soap in water and BAM perfect liquid soap!!

Yeah no... If you want liquid soap you need KOH - lotsa places to buy it online if you are in the US :)
 

DeeAnna

Well-Known Member
Joined
Feb 20, 2013
Messages
13,563
Reaction score
19,689
Location
USA
If you think of sodium from the NaOH and potassium from the KOH as being magnets in your soap, then here's a way to think about the difference.

The sodium "magnet" is VERY strong and fastens the the molecules of soap firmly together into a solid bar soap. If you mix a lot of water with a sodium soap to try to turn it into a liquid soap, the mixture might be liquid at first, but the sodium magnet does not give up. It might take some time, but the sodium will eventually fasten those soap molecules together to form a more organized structure again. That is what makes a sodium-based "liquid soap" turn back into a firm non-pourable jelly or have an unpleasant ropy or slimy texture.

A potassium "magnet" is more gentle, so it links the soap molecules more loosely. Because the soap molecules are less organized and are free to slide and slither around each other, the result is a soft soap paste or liquid soap that pours easily and stays that way.

I hope this helps!
 

Spice

Supporting Member
Supporting Member
Joined
Mar 21, 2014
Messages
681
Reaction score
227
Location
NorCali
NaOH (sodium hydroxide) makes bar soap. The structure of the molecules once saponification takes place is a rigid crystalline structure. (If I recall DeeAnna's explanation correctly.) Using NaOH to make soap that you then attempt to dilute to make liquid soap will result in a snotty consistency mess that does not function as soap. IN MY EXPERIENCE. Others have other results. But I have tried this over and over, and nothing but snotty non-soapy soap results.

KOH (potassium hydroxide), when saponified, has a looser structure. This yields a paste that can then be diluted for good liquid soap.

Some folks use dual lyes- KOH + NaOH to get supposedly thicker liquid soap. This has not been my experience. However, NaOH is a good bit cheaper for me to buy. So, if I am making some sort of household soap (dish or laundry), I will often use 20-30% NaOH to reduce the cost, without negatively affecting the cleansing power. It does reduce the lather, which is a good thing in a laundry soap.
I remember when I was new and I had hopes that NaOH lye could be used to make liquid soap - and everyone on the internet (it seems) tells you to just dissolve a grated bar of soap in water and BAM perfect liquid soap!!

Yeah no... If you want liquid soap you need KOH - lotsa places to buy it online if you are in the US :)
If you think of sodium from the NaOH and potassium from the KOH as being magnets in your soap, then here's a way to think about the difference.

The sodium "magnet" is VERY strong and fastens the the molecules of soap firmly together into a solid bar soap. If you mix a lot of water with a sodium soap to try to turn it into a liquid soap, the mixture might be liquid at first, but the sodium magnet does not give up. It might take some time, but the sodium will eventually fasten those soap molecules together to form a more organized structure again. That is what makes a sodium-based "liquid soap" turn back into a firm non-pourable jelly or have an unpleasant ropy or slimy texture.

A potassium "magnet" is more gentle, so it links the soap molecules more loosely. Because the soap molecules are less organized and are free to slide and slither around each other, the result is a soft soap paste or liquid soap that pours easily and stays that way.

I hope this helps!
This is just what I needed. I understand the difference of Noah vs KOH and with that I can start to make my liquid soap. I have enough to start. I must likely be asking for all kinds of advice as I get started. Thanks to all.:wave::wave:
 

Susie

Supporting Member
Joined
Aug 1, 2013
Messages
9,744
Reaction score
9,279
Location
Texas
You keep asking questions. There are lots of folks who don't know enough yet to even know what to ask. You help them tremendously with each question.
 

LittleCrazyWolf

Well-Known Member
Joined
Jan 6, 2015
Messages
192
Reaction score
142
Location
East Coast
DeeAnna, I just wanted to say that was a fantastic way of explaining the difference. I plan to try liquid soap sometime in the near future so I was lurking.
 
Top