Soda Ash Eruptions

[Becky1024]

I made two batches of cold process soap one day a month ago in loaf molds, cut them and left to cure covered under a light cotton towel. Uncovered them yesterday, and one batch looked fine, the other had white powdery eruptions on the cut sides of the bars. The tops, sides and bottoms of the bars look fine. The only difference in the batches was the colorant and essential oils. I'm convinced the white powder is soda ash - it tastes bitter, not like lye, and dissolves in water quickly. I wish I had taken pictures before I scraped and washed all the ash off! I had this happen once several years ago with a couple of soaps that I CPOPed and thought the oven temperature was too hot. Now I'm wondering if this batch got too hot even though I didn't CPOP it.

What are your thoughts? Here's the recipe. The salt and citric acid were thoroughly dissolved in the water before adding lye, and then the lye was thoroughly dissolved. The soaping temperature was lye 102 F / oils 110 F , which are pretty typical temperatures for my batches. The loaf was gelled by wrapping a few towels around it, and the bars were cut a day later. The ingredients are ones I use all the time, except the vetiver which was hidden in the back of my essential oil cabinet and hasn't been used for a couple of years.

NaOH lye	150 g​
water	209 g​
salt	7 g​
citric acid	21 g​
	​
	​
olive oil	526 g​
coconut oil	177 g​
shea butter	296 g​
castor oil	52 g​
	​
lemongrass EO	14 g​
vetiver EO	14 g​
patchouli EO	14 g​
cocoa powder	2 tsp ​

 

[AliOop]

More heat will speed up saponification, typically reducing the chance of soda ash. So extra heat should not be the problem, unless maybe there was some heat-generated reaction with the silicone mold. But that doesn't sound like a possibility in your case, since you mentioned that it was on the cut sides, not the mold sides.

Certain additives, including AC, cocoa powder, some EOs, and certain micas (esp purples and blues) cause ash on my soaps, no matter what else I do to prevent it, including heat, low water, covering, spraying with alcohol, etc.

Your process included heat and low water, so my best guess would be the cocoa powder or one of the EOs. It is weird that it only happened to some of the soaps, but maybe they had more air exposure somehow? Or perhaps those particular surfaces were not as far along in the saponification process as the rest of the soap.

 

[KiwiMoose]

Sometimes there is no rhyme or reason as to why soda ash occurs. Gelled soap is less likely to ash, but it's not immune. Mine rarely get ash on the silicone sides or even the cut soap - but often on the very top.
Sometimes it can be climate related - sometimes the EO I use. If I get it now I just 'wash' it off.

 

[Becky1024]

More heat will speed up saponification, typically reducing the chance of soda ash. So extra heat should not be the problem, unless maybe there was some heat-generated reaction with the silicone mold. But that doesn't sound like a possibility in your case, since you mentioned that it was on the cut sides, not the mold sides.

Certain additives, including AC, cocoa powder, some EOs, and certain micas (esp purples and blues) cause ash on my soaps, no matter what else I do to prevent it, including heat, low water, covering, spraying with alcohol, etc.

Your process included heat and low water, so my best guess would be the cocoa powder or one of the EOs. It is weird that it only happened to some of the soaps, but maybe they had more air exposure somehow? Or perhaps those particular surfaces were not as far along in the saponification process as the rest of the soap.

I should have mentioned that it was a drop swirl, so only parts had cocoa powder. But colored and uncolored alike had the ash eruptions. The Eos were in both parts. I haven't used the vetiver in awhile, but use both lemongrass and patchouli EOs quite a bit and have never had problems with them. Also used the vetiver in the other batch I made the same day that turned out fine. Its a mystery!

 

[Zing]

I had soda ash one time. Now after pouring, I spray with alcohol, cover with plastic wrap, then cardboard. I gell so I add a pile of towels as well. I have not gotten soda ash ever since with my loaf molds.

With my single cavity molds, I've learned to prevent soda ash by keeping them in the molds for 5-7 days before unmolding.

And my trick to deal with unexpected results is to call it "rustic." Good luck!