20% Castor | CP±OP | 2% Vinegar

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Notorious Lyear
Jan 14, 2021
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Finally, tackling that open question back then in the Castor thread: How can high-castor soaps appear translucent-gummy to some, but rough and chalky to others? And does vinegar (sodium acetate) play a role here?

Well. There is probably a way to find this out.
Recipe: 20% of each castor, sesame, coconut oil, mango butter, and palm stearin.


Variation parameters:
  1. H: forced gel (CPOP) or C: suppressed gel/false trace (fridge)
  2. adding (A) or not (no A) vinegar to the lye water (accounted for with NaOH dosage)
So (four weeks ago) I made the oil blend, split it into two, and added 33% lye to each, but with 2%TOW of sodium acetate added to one. Then I distributed the batter over two small silicone moulds each. One pair went into the oven to full-blown CPOP, the other into an ice water bath, and overnight into the fridge, to avoid gel at any cost.
Please don't judge my dosage skills to aim for equally sized soaps.
One thing to notice is that even in CP batter, the acetate helped with a smoother, more easily pourable batter, that gave a more even top (but also more soda ash, and a weird texture).



I had used the very same oil blend before, and noticed that it's really eager to gel even in small 25ish gram moulds. It had went fully opaque and rock hard within one hour or so, and so it did this time as well (both the ones with and without acetate). But just to be sure CPOP to enforce things.

The aggressively cooled soap cubes did have some cohesion issues (particularly the one with acetate – it broke apart during unmoulding), but the CPOP ones as well to some degree – see later on.
False trace could be part of the issue, but this isn't the whole story. The CPOP'd HA (bottom right) does not only look like it consists entirely of soda ash, it also behaves like that!


One weird thing to note is that CPOP gave rise to some shrinkage. More pronounced with the acetate-free pair of soaps, warm reaction gave a bar that was noticeably contracted. Or did the acetate cause expansion, like the crackling pattern on the CA soap ash might suggest?

The look & feel
The only soap that gave the impression to be decent was the H soap. The others shared the same bright white appearance and weird chalky, plaster-like touch that high-castor soap isn't well-known for, but I had been observed before.
Not sure where the air bubbles on the surface of the H soap come from. Maybe CPOP + gel/reaction temps were so high that the soap went all the way up to in-situ HP and some water boiled off? This would fit with the HP-like appearance, but doesn't explain why it didn't happen as well to the HA soap, that has been in the oven at exactly the same conditions (the only difference: the 2%TOW vinegar).

Within the tested parameters, this recipe can not reproduce the gummy, translucent look that others (including myself) have reported from castor-heavy soaps. The H soap is indeed somewhat translucent, but no more than any other HP soap.


Lather & dissolution speed
This is where things becane really awkward. I'll start with the H soap, since it is the only that IMHO deserves the name “soap” at all. At the sink, it behaved like an average HP soap. Not impressive, but nothing to hunt for either. Have had better soaps from these ingredients. But no trace of the proverbial stickiness and slipperiness that castor is said to impart to soap when overdosed.

The three other pieces were entirely different – to a point where I hesitate call them soap at all! First, the texture, that loosely reminds of (mediocre) salt bars, as if soda ash formation had progressed throughout the entire bar. Or think of wet chalk. Very dominant graininess. Even when rubbed, zero viscous/creamy suds. Nothing to lather up with the hands, a lather that is worse than a young castile soap. And oh boi, did I try. Just look at the before/after pics: I've used up nearly half of the HA soap during one hand wash test! Still no lather to speak of!
I easily could indent the HA soap with my fingernail, to test hardness/inner texture. Somewhere between half set-hard gypsum plaster, and ice cream. No fun.

This experiment confirms my previous observations that highish-castor soaps can develop a gritty, chalky texture, and it sheds some light upon the conditions at which this happens. It appears to be favoured by not forcing gel, and vinegar/acetate addition. However, neither is necessary to achieve this. From these findings I'd call acetate incompatible with (elevated) castor. Yet, not adding vinegar does not guarantee that the wet chalk phenomenon wouldn't occur – acetate is not the main culprit.
In balanced soap recipes (hardness 42, longevity 28, PUFA 12), there is no point for that high castor addition. 5% do boost lather, but 20% don't add anything (if you're in luck), or completely destroy it. In line with what others have reported from 100% castor soap bars as well as my findings with castor LS foam decay and viscosity ruining, it appears that generous castor additions lead to a quicker decay of lather, up to the point where it doesn't form at all.
One step further in a theory what this “boosting” effect might be all about: castor speeds up the readiness of a soap to go from solid into (runny) liquid. In small additions, it can help the other soaps to enter that “gel” state that feels like “slime”, but can be easily whipped up to lather; but larger castor levels liquefy the whole suds and prevent bubbles altogether.

What now?
This was some four weeks into cure. I don't expect the soaps to change much with time. I will probably grate/grind them up (or smash them with a hammer, lol), to sprinkle into confetti or rebatch or HP soap. Dilute the castor to the point where it can play off its strengths without getting into the way of itself.
And keep the castor close to the folkloristic 5% in future recipes.