ResolvableOwl
Notorious Lyear
This is kind of a follow-up to this post/discussion initiated by @Orla that didn't go out of my head … until I would make my own hands dirty. 
Short recap: Palmitic and stearic acids are most often mentioned in one breath (“hardness”, “longevity”, “creamy lather”, “solubility”, “stearic spots”…). Still, the two acids are not identical. How far can you safely swap one for the other, and which differences are to consider? Is japan wax or hydrogenated vegetable oils (and/or a blend of both) the last word in making hard, long-lasting no-palm soaps without the need for fancy butters?
Many hard oils/butters and most recipes contain both acids in a somewhat balanced ratio, and the vote with the feet corroborates this. P:S is most often around 1:1 to 2:1 – to little surprise: in most recipes palm, lard, tallow, cocoa butter, butter blends, and/or rice bran oil have a finger in the pie.
But what are we missing when we stay within this comfort zone of well-proven recipes?
There's a way to find out. Roughly orienting on Orla's efforts, I played around with soap calculators and came up with the following two literally eccentric recipes:
P: 33% rice bran oil, 33% HO sunflower, 25% Japan wax
S: 63% cupuaçu butter, 21% HL sunflower, 7% hydrogenated canola wax
Each also contains 9% palm kernel oil as a lauric oil, as well as ROE. 6% lye discount; dual lye with 8% NaOH swapped by KOH (to compensate the missing castor oil/increase solubility/reduce castile slime).
Of each batter, I poured two thirds into a mould, and mixed the remainders to make a third bar of the same size. CPOP time!
Some process remarks: Japan wax has a strong tendency to evoke false trace (particularly at this high addition rate) if handled just a few degrees too cool (note to myself: water bath next time). Contrary, the cupuaçu batter was “too well-behaved” and traced so slowly that the emulsion sedimented. I noticed after half an hour and gave it a mix; now they're all three sitting in the oven, experiencing a thorough gel phase.
With the obvious P/S exception, the recipes are fine-tuned to be as similar as possible. About 40% oleic and 13% poly-unsaturated. All the property numbers virtually identical, and INS/iodine as close as imaginable. Since the molecule chains of palmitic acid are shorter than stearic, the P soap has a higher saponification value, hence it contains more water and alkali %ppo. (This is inevitable, unless I had summoned some black magic with esoteric acids like palmitoleic, arachidic or erucic.)
The P soap has a P:S ratio of 7.2:1, while the S recipe calculates P:S to about 1:3.6 (caveat: this number is not very precise, since due to laziness/missing information, I treated the hydrogenated canola like the 100% hydrogenated soy like offered by many calculators. I have reasons to assume that my stuff is not fully hydrogenated, but at least partially elaidic). More extreme P:S ratios were not possible within limits of reasonable soap recipes, unless I had expanded my oil/butter/wax library even further. In fact, the above mentioned thread was (one of the) reasons why I had bought Japan wax in the first place.
I now have three soaps that are identical from their fatty acid profile – except for one that obtains its hardness virtually exclusively from palmitic acid, the second from stearic acid, and one in between with equal amounts of either. Tomorrow is picture time! A few days in, I'll start comparing their mechanical hardness, solubility/lathering, and skin feel.
Short recap: Palmitic and stearic acids are most often mentioned in one breath (“hardness”, “longevity”, “creamy lather”, “solubility”, “stearic spots”…). Still, the two acids are not identical. How far can you safely swap one for the other, and which differences are to consider? Is japan wax or hydrogenated vegetable oils (and/or a blend of both) the last word in making hard, long-lasting no-palm soaps without the need for fancy butters?
Many hard oils/butters and most recipes contain both acids in a somewhat balanced ratio, and the vote with the feet corroborates this. P:S is most often around 1:1 to 2:1 – to little surprise: in most recipes palm, lard, tallow, cocoa butter, butter blends, and/or rice bran oil have a finger in the pie.
But what are we missing when we stay within this comfort zone of well-proven recipes?
There's a way to find out. Roughly orienting on Orla's efforts, I played around with soap calculators and came up with the following two literally eccentric recipes:
P: 33% rice bran oil, 33% HO sunflower, 25% Japan wax
S: 63% cupuaçu butter, 21% HL sunflower, 7% hydrogenated canola wax
Each also contains 9% palm kernel oil as a lauric oil, as well as ROE. 6% lye discount; dual lye with 8% NaOH swapped by KOH (to compensate the missing castor oil/increase solubility/reduce castile slime).
Of each batter, I poured two thirds into a mould, and mixed the remainders to make a third bar of the same size. CPOP time!
Some process remarks: Japan wax has a strong tendency to evoke false trace (particularly at this high addition rate) if handled just a few degrees too cool (note to myself: water bath next time). Contrary, the cupuaçu batter was “too well-behaved” and traced so slowly that the emulsion sedimented. I noticed after half an hour and gave it a mix; now they're all three sitting in the oven, experiencing a thorough gel phase.
With the obvious P/S exception, the recipes are fine-tuned to be as similar as possible. About 40% oleic and 13% poly-unsaturated. All the property numbers virtually identical, and INS/iodine as close as imaginable. Since the molecule chains of palmitic acid are shorter than stearic, the P soap has a higher saponification value, hence it contains more water and alkali %ppo. (This is inevitable, unless I had summoned some black magic with esoteric acids like palmitoleic, arachidic or erucic.)
The P soap has a P:S ratio of 7.2:1, while the S recipe calculates P:S to about 1:3.6 (caveat: this number is not very precise, since due to laziness/missing information, I treated the hydrogenated canola like the 100% hydrogenated soy like offered by many calculators. I have reasons to assume that my stuff is not fully hydrogenated, but at least partially elaidic). More extreme P:S ratios were not possible within limits of reasonable soap recipes, unless I had expanded my oil/butter/wax library even further. In fact, the above mentioned thread was (one of the) reasons why I had bought Japan wax in the first place.
I now have three soaps that are identical from their fatty acid profile – except for one that obtains its hardness virtually exclusively from palmitic acid, the second from stearic acid, and one in between with equal amounts of either. Tomorrow is picture time! A few days in, I'll start comparing their mechanical hardness, solubility/lathering, and skin feel.
. Obviously, my CPOP-late mixing was not thorough enough to stir up all of the settled lye, yet so strong that it destroyed the finish, and it looks as rustic as HP soap now, plus that whitish stuff at the bottom. So far, no hints of stearic spots, but the upper (translucent) phase still feels greasy.
