Making soleseife with potassium chloride salt?

[Morning Glory]

Has anyone tried making soleseife with potassium chloride? I've been reading about the wonders of dual lye bar soap and I'm wondering if dual salt soap would have any benefits.

I thought I'd ask you all before putting in my order for potassium hydroxide to see if it would be worth ordering potassium chloride as well.

 

[DeeAnna]

A "dual lye" bar soap is typically made with an alkali solution of 5% KOH with the remainder as NaOH. My comments here are based on making soap with this type of alkali solution.

This percentage is not a weight percentage, by the way. Dual-lye percentages are based on the proportions of alkali molecules, not the proportions by weight.

Soleseife soap is typically made by adding enough sodium chloride (NaCl) in plain water to make a saturated solution. At room temperature, roughly 1 part NaCl by weight can be dissolved in 3 parts plain water. In other words, in 100g of this saturated solution, there would be about 25g NaCl and 75g water.

The solubility of potassium chloride (KCl) in water is about the same as NaCl in water, so you can dissolve roughly 1 part KCl in 3 parts water by weight.

If you make a saturated solution of KCl like this and used this solution to make soap, you'd be adding a LOT more potassium to the soap than if you use a dual-lye solution. There would be a real risk of making soap that is more like a liquid soap paste than a solid bar soap.

To mimic a 5% dual-lye alkali solution using KCl instead, you'd need to determine the amount of potassium (K) supplied by the dual-lye solution. Then translate that into the weight of KCl that would supply the same amount of potassium. Then make the solesiefe brine with that amount of KCl and enough extra NaCl to make up the difference.

It's a do-able task if you're comfortable with the chemistry and math and interested enough to try the experiment.

 

[Morning Glory]

A "dual lye" bar soap is typically made with an alkali solution of 5% KOH with the remainder as NaOH. My comments here are based on making soap with this type of alkali solution.

This percentage is not a weight percentage, by the way. Dual-lye percentages are based on the proportions of alkali molecules, not the proportions by weight.

Soleseife soap is typically made by adding enough sodium chloride (NaCl) in plain water to make a saturated solution. At room temperature, roughly 1 part NaCl by weight can be dissolved in 3 parts plain water. In other words, in 100g of this saturated solution, there would be about 25g NaCl and 75g water.

The solubility of potassium chloride (KCl) in water is about the same as NaCl in water, so you can dissolve roughly 1 part KCl in 3 parts water by weight.

If you make a saturated solution of KCl like this and used this solution to make soap, you'd be adding a LOT more potassium to the soap than if you use a dual-lye solution. There would be a real risk of making soap that is more like a liquid soap paste than a solid bar soap.

To mimic a 5% dual-lye alkali solution using KCl instead, you'd need to determine the amount of potassium (K) supplied by the dual-lye solution. Then translate that into the weight of KCl that would supply the same amount of potassium. Then make the solesiefe brine with that amount of KCl and enough extra NaCl to make up the difference.

It's a do-able task if you're comfortable with the chemistry and math and interested enough to try the experiment.

Thank you for all this information! It will help me design my experiments better. I gotta say the fact that no one else seems to have done this makes me want to try it even more. I'll post my results when they're ready.

 

[Morning Glory]

Update.

I made three test batches each a day apart. They all were made with olive oil, a 37% lye solution, and a 5% superfat.

3.5% sodium salt brine
5.55% potassium salt brine
11.1% potassium salt brine

When carving the date into the bars the 5.55% potassium bar was harder at 24 hrs than the 3.5% sodium bar at 48 hrs. They are CPOP so I suppose it's possible this is due to gelling inconsistently. 24 hrs after that (72 hrs for sodium and 48 hrs for potassium) the carving hardness inverted with the sodium bar being a smidge harder. For shaving hardness the sodium bar is quite brittle. The 11.1% potassium bar is softer for carving the date. I have not shaved its edges yet as it is still in its mold.

I shaved off pieces of the 3.5% sodium bar, 5.55% potassium bar, and another OO bar I made two weeks ago and when washing they all felt about the same to me. I am inexperienced at soap making so I'm not sure if there was something to notice or not.

The 11.1% potassium lye solution became very cloudy while the others did not. It also took longer to get to trace. It strangely seemed to come to trace but after I had removed the stick blender and wiped the batter back into the container it wasn't at trace any more. I don't know what to make of that.

 

[AliOop]

The 11.1% potassium lye solution became very cloudy while the others did not. It also took longer to get to trace. It strangely seemed to come to trace but after I had removed the stick blender and wiped the batter back into the container it wasn't at trace any more. I don't know what to make of that.

My best guess is that this is due to what DeeAnna warned you about above, to wit:

If you make a saturated solution of KCl like this and used this solution to make soap, you'd be adding a LOT more potassium to the soap than if you use a dual-lye solution. There would be a real risk of making soap that is more like a liquid soap paste than a solid bar soap.

What you described (appearing to trace, and then the emulsion broke when you stopped blending) is exactly how liquid soap batter usually behaves for me. It takes a long time to come to actual trace. There will be a few times before that where it appears to be emulsified/ traced, but won't stay that way if I stop blending at that point. My understanding is that's because potassium hydroxide is a weaker alkali than sodium hydroxide, and thus takes far more mixing to reach a stable emulsion. And apparently there is some correlation to that phenomenon when adding potassium chloride, as well.

 

[Morning Glory]

Update

I redid my lather tests with the 3.5% sodium soap, no salt soap, 5.55% potassium soap, and 11.1% potassium soap. This time I was checking for how long it took for a dry freshly shaved curl to lather. The results were what you would expect them to be with the sodium soap taking it's sweet time to lather, followed by no salt soap, 5.55% potassium soap, and 11.1% potassium soap as the quickest. I hadn't paid attention before to how long it took to lather. The hardness/brittleness of the bars also follows the same pattern.

I ordered potassium hydroxide and hope to find time this weekend to making a couple small batches of different concentrations to compare. I'll update this thread when that eventually happens.