My experience with Sodium Lactate

[Ozzietx]

I have read that sodium lactate will help harden soap and can harden soap quicker than without.
I decided to try sodium lactate as I was also going to use silicone loaf molds. I have read sodium lactate can help
soaps de-mold from silicone molds easier. I typically use 3" PVC for molds for my round soap bars. With my regular recipe
I can usually de-mold in about 18-24 hours. Once I incorporated the sodium lactate( one tsp PPO) my curing time went up
significantly. I had to wait 48 hours, and the soap still seemed very soft. Both in my PVC molds and the Silicone soap mold. When I cut the soap, it seemed much more crumbly.
I am not really seeing the benefit for me. Has anyone else experienced a similar result? Am I doing something wrong?

 

[DeeAnna]

Context is important when using additives to "solve" problems.

Your soap recipe already is rich in palmitic and stearic fatty acids -- rich enough to produce a hard soap all on its own fairly soon after saponification is finished. The fact that you can remove the soap from molds at 18-24 hours is proof of this.

So you already have soap that's already hard fairly quickly. It doesn't make sense to then add one or more salts (sodium lactate is a salt) to improve a situation that's already at an optimum.

Most bar (NaOH) soap makers don't realize that adding salts can have the paradoxical effect of softening bar soap that's already at optimum hardness. Liquid (KOH) soap shows this effect more clearly than bar soap -- we know salts can add thickness to liquid soap, but only to a point. Adding salt(s) beyond that optimum point actually causes the soap to become thinner. In bar soap, the effect is similar in that salts added beyond the optimum amount will tend to increase the softness of the soap.

One soap maker was having problems with their soap some time ago due to this effect. They were adding several sodium-based salts to their soap. Each of the salts was used at a normal dose, so there was no concern there. But there were several salts being added -- I don't recall what they were doing exactly, but it was something like adding sodium citrate as a chelator, sodium lactate for easy unmolding, and sodium chloride (table salt) for greater hardness. The combined effect of this high overall load of salts caused the soap to become softer and rubbery. Once the soap maker eliminated some of the salt load, the soap was no longer overly soft.

If your soap isn't ready quite soon enough to suit you, you might try increasing the lye concentration a bit -- maybe try 35% rather than 33% -- and see if that is helpful.

And/or try soaping slightly warmer to ensure the soap goes into gel during saponification. Your comment that the soap was crumbly is a hint that this particular batch of soap might not have gotten warm enough during saponification.

And/or refrigerate the finished soap to cool the outer surface enough so the soap can be removed from the mold.