KOH Potassium hydroxide

[SweetHoneyHandmade]

Has anyone here successfully made soap with potassium hydroxide rather than sodium hydroxide? Anecdotally I’ve heard it’s what is used for liquid soap and soap paste, but I’ve come across instructions for a hard soap bar using it.

 

[artemis]

Try a quick search for KOH and another for potassium hydroxide. Lots of information.

 

[DeeAnna]

Thread about KOH and NaOH in bar soap: https://www.soapmakingforum.com/threads/dual-lye-castile.59747/
SMF Liquid and Cream Soap forum: https://www.soapmakingforum.com/forums/liquid-soap-and-cream-soap-forum.40/
Liquid soap tutorial: https://www.soapmakingforum.com/threads/soaping-101-liquid-soapmaking-video.46114/unread

 

[SweetHoneyHandmade]

I’m more trying to find out if anyone’s had success making hard bar soap from KOH, not using NaOH at all. I have mine in my mold atm, but it still feels a bit springy. I added a tablespoon and a teaspoon of salt before it came to trace, wondering if that’s enough salt to firm it up.

 

[artemis]

I know I have seen posts with similar questions. The answers were not in favor of it, but I don't remember the details. Were you unable to find any such posts when you searched?

 

[SweetHoneyHandmade]

I have done searches for “KOH” and “potassium hydroxide.” Some things I’ve read said [NaOH] soap can be firm the day after pouring into the mold, and mines not. But all the stuff I read about KOH soap is that it will NEVER firm, but mine is (sort of). So I feel like I’m in no man’s land... not really a true KOH soap since I added salt, and not a true bar soap since I used a different lye.

 

[DeeAnna]

I don't know what you're defining as a "firm" soap. Firm as NaOH soap that you can't dent with hard finger pressure? Firm as in holds its shape as long as you don't squish or poke at it?

I make shave soap with 100% KOH. While it will get firm-ish if given enough time to dry, it is never hard-like-a-rock like NaOH soap. I can easily squish it with moderate hand pressure even months after it's made.

All of the historical books I've read about soap making jive with this personal experience. KOH soap is a soft soap. Even if you add salt (sodium chloride) to firm it up by substituting sodium (Na) for some of the potassium (K), it still won't be hard like NaOH soap.

edit -- The other problem is you're not providing all of the background for your question, so people can give you decent advice. I gather from your other thread that this is wood-ash lye that you're using. Wood ash lye is not KOH. While you can end up with a potassium soap using wood-ash lye, the soap will also contain impurities that will affect the properties of this soap. This is not the same kind of soap as you get when making soap with commercial KOH.

 

[SweetHoneyHandmade]

I gather from your other thread that this is wood-ash lye that you're using.

Thank you for taking the time to read and respond. Yours is the clearest response about KOH and soft soap I’ve read and it makes sense to me now. Thank you!

ETA: I just told my husband the soap I’ve made will be his new shave soap, and we both seem pretty pleased with that. Thank you DeeAnna

 

[Richard Perrine]

Thank you for taking the time to read and respond. Yours is the clearest response about KOH and soft soap I’ve read and it makes sense to me now. Thank you!

ETA: I just told my husband the soap I’ve made will be his new shave soap, and we both seem pretty pleased with that. Thank you DeeAnna

Making hard soap with KOH seems to be a lost and forgotten art from, but it is very possible once not an uncommon way to make soap (with potash).

https://www.soapmakingforum.com/threads/making-hard-soap-with-potassium-hydroxide-koh.71629/

Most of the KOH soaps I make harden within 30 minutes to a couple of hours and are or seem to be as hard as my lye soaps. They do not last as long, but the difference in longevity is not dramatic.

 

[karon L adams]

yes, but remember, KOH has a different molecular weight than NaOH, so you must correct for that when changing your recipe. also, a potassium salt of a fatty acid is softer than a sodium salt. so you will get a softer soap.

 

[Richard Perrine]

Hmmm. I thought I had included my recipe on the thread regarding my exploration of KOH soap. Yes, the soap is softer, but not too dramatically softer. The process is different for sure. It is important to use a high percentage of oils that will help make a harder soap. I added a lot of soy wax. Try other oils. I find the bars to be creamier and less stringent. Here is my tried and true recipe:

Potassium Hyroxide (Potash) Hard Soap

Single Bar Recipe

60g Soy Wax (2.11oz)
15g Coconut Oil (.53oz)
15g Castor Oil (.53oz)
10g Canola Oil (.35oz)


15g Salt (Himalayan Pink or other fine pure salt) (.53oz)
38g Distilled Water (1.34oz)
22.4g KOH (.79oz)

-I grind the salt in a mortar and pestle so that it is of fine powder texture. Dissolves and distributes better.
-Add salt in hot water to dissolve. Use the water set aside for the KOH. The added heat from the reaction with KOH aslo helps to dissolve more of the salt. A slighly creamy mixture should form.
-Add hot oils to the potash/salt mixture.
-Stir and mix.
-Add colouring. Mix.
-Add fragrance. Mix quickly and pour

 

[SweetHoneyHandmade]

Thank you so much Richard for including your recipe! I regard you as the KOH pioneer, from previous posts in the forum I’ve read!

 

[karon L adams]

yeah. molecule for molecule, it works out the same, but the fact that the molecular weights are different is what sets up the difference in the amounts needed. and, yes, using oils that make harder soaps is the best way. stay away from liquid oils, unless the goal is a liquid soap.

 

[Richard Perrine]

Thank you, but I only modified a process someone else created some time ago. [emoji6] I’m surprised there isn’t more information on this or I’m just not seeing it.

 

[karon L adams]

there's a couple of reasons. KOH is easier to come by now that it was in 1990, when I started this stuff. but it still is not as common. and not a lot of folks really know how to use it. the books I was reading back then were written in the 1800's and most of them were written FOR KOH and I had to convert for NaOH, but naOH was always easier to get, especially in 55 gallon barrels. and back then, Na was in bead form and the only KOH I could get was flake. not a huge problem but a little harder to handle. in the end, I preferred the soap I got from NaOH, so that was all I used. I sold KOH for those who wanted it. most people used it strictly for making liquid soap back then.

 

[Richard Perrine]

Karon. It is clear that using KOH would be less cost efficient. I also found using KOH limited me from being a little more creative.[emoji5] I like the texture and feel of it.

 

[karon L adams]

oof, I have no idea about that. I haven't bought any of them in so long, I have no idea what it costs. the difference in weight isn't really enough to make a significant difference in the cost of the soap. it's just a question of getting the chem right.