- Jan 14, 2021
- Reaction score
|NaOH:KOH mass ratio||100:0||97:3||89:11||100:0 + sorbitol|
|Na:K molar ratio||100:0||98:2||92:8||100:0 + sorbitol|
|Lye concentration XOH/(NaOH+KOH+H₂O)||38.3% | 0%||37.5% | 1.1%||35.2% | 4.3%||38.3% | 0% | 3.1% sorbitol|
All made from the same oil blend (30% HO sunflower & RBO, 15% macadamia, plus just enough hard oils to make them harden up in a reasonable time). It has plenty MUFA (52% oleic acid, 3% palmitoleic acid), so it should be somewhat prone to oleic slime. No lauric oils added, to not distort bubbliness properties by coconut & friends (still 5% castor though).
Additives: ROE + 0.8%TOW citric acid. The rightmost bar has another 1.1%TOW sorbitol added, so that I can compare the behaviour of the dual-lye bars with the one of a known bubble booster.
With dual-lye, I have to choose one fixed concentration parameter. I went for the lye molarity of 9.58 mol hydroxide per kg lye (that's why the XOH mass concentration increases with KOH content, because KOH is heavier per mole than NaOH). No idea if that makes sense from a fundamental point of view, but it made sense from my masterbatch blending technique.
- Does a few % of KOH make overly soft bar soap, to a degree where it impedes unmoulding? Apparently not! Following up @KiwiMoose reports of an “emergency dual-lye” batch that went just fine, I was surprised and wanted to know better. The recipe is rather soft, so I gave it two days, and the hardness of all three Na/K soaps was essentially the same. Only the one with sorbitol (right) has a different texture (a bit of a chalky/velvety feel) to it. Not sure if the partially speckled look (stearic spots? false trace? separation? You'll never know with microbatches…) has to do something with the lye composition; the sample size is too small to decide (and has other error sources, like varying temperature of oils and lye between the batches). The bar with sorbitol had much worse soda ash issues than the other three, but once again it's too early to draw conclusions from this observation.
- Three data points for the oleic slime reducing properties of a few % of KOH. (Part of the reason why I have formulated the recipe as high-oleic)
- Bubbliness? The logic: KOH → increased solubility → less slime: is suggestive as well to increase the willingness of the soap to give off lather. Some folks around here have made good experiences with the lather of dual-lye, and this trial can add some grounding to it. (Part of the exclusion of lauric oils, to interfere less with subtle changes in lathering ability.)
- Easier solubility sounds like worse longevity? Let's find out!