Help needed - Hardness and Longevity

[Mobjack Bay]

I need some help understanding the various options I have for increasing the hardness and longevity of a soap, aside from the cure. Here’s what I *think* I know:

• Increasing the percentages of palmitic and stearic FAs will increase hardness and longevity, and enhance dense, creamy lather (I am not interested in increasing CO).
• Using a high percentage of OO will produce a hard soap over time. Is this a function of the high oleic acid percentage, or something unique about OO? Do the soap calculators give a reasonable approximation of longevity when the percentage of oleic acid or OO is high?
• Adding salt will increase hardness and longevity, but also reduce lather if the recipe is held constant.
• Adding vinegar will increase hardness. I have no idea how vinegar affects longevity and lather or why.
• Adding beeswax will increase hardness. Ditto what I said for vinegar, but maybe the answer is in the soap calculator or on the forum.
• Adding a small percentage of stearic acid would be similar to adjusting a recipe to have a similar percentage of stearic added via a base fat (this is going out on a limb based on my existing knowledge and no experience with stearic acid...)

TIA for any useful threads or insights you can provide.

 

[DeeAnna]

A soap high in oleic acid (aka olive oil soap) is highly water soluble. While this type of soap may be physically hard-like-a-rock, especially after cure, it will never be a particularly long lived soap.

The soap calcs use the % of palmitic + stearic + myristic + lauric to estimate hardness. That's basically a measure of hardness shortly after the soap is made to give the soap maker some idea of how quickly a soap can be removed from the mold.

Longevity is the sum of palmitic + stearic. These fatty acids make soap that is almost insoluble in water, which is why it makes sense to use them as a measure of how long a soap will last.

The % oleic acid is not (and IMO should not) be included in either property as the soap calcs define them.

Salts -- table salt (sodium chloride), sodium acetate (vinegar + NaOH), etc. -- harden soap by causing the soap to "salt out". Salting out is what happens when soap molecules become less soluble in the water phase due to the addition of salts, alkalis, and other chemicals.

Beeswax doesn't trigger "salting out" so, while it adds hardness, it's not doing so by the same process that salts add hardness.

 

[Mobjack Bay]

A soap high in oleic acid (aka olive oil soap) is highly water soluble. While this type of soap may be physically hard-like-a-rock, especially after cure, it will never be a particularly long lived soap.

The soap calcs use the % of palmitic + stearic + myristic + lauric to estimate hardness. That's basically a measure of hardness shortly after the soap is made to give the soap maker some idea of how quickly a soap can be removed from the mold.

Longevity is the sum of palmitic + stearic. These fatty acids make soap that is almost insoluble in water, which is why it makes sense to use them as a measure of how long a soap will last.

The % oleic acid is not (and IMO should not) be included in either property as the soap calcs define them.

Salts -- table salt (sodium chloride), sodium acetate (vinegar + NaOH), etc. -- harden soap by causing the soap to "salt out". Salting out is what happens when soap molecules become less soluble in the water phase due to the addition of salts, alkalis, and other chemicals.

Beeswax doesn't trigger "salting out" so, while it adds hardness, it's not doing so by the same process that salts add hardness.

Brilliant answer! Thank you! Now that I finally have a good basic understanding of how soaps with different FA profiles feel and lather, I will be turning my attention to hardness and longevity. As it turns out, none of the many non-lard recipes I’ve made to date have more than 34% stearic + palmitic. My high p+s recipes are palm-rich and I like them, but they definitely challenge my soap making skills due to how fast they trace compared with my other recipes.

 

[Mobjack Bay]

Does anyone make a recipe that is around 40% combined stearic & palmitic FAs? I’m not having much luck finding the right information using a search. If so, can you tell me more

and @DeeAnna based on what you wrote above, It seems as if the net effect of adding salt vs. more stearic & palmitic could be the same for longevity. I think this means that if I like the lather quality I could add a bit of salt to make the soap harder. If the lather could stand to be denser and creamier, I should probably try increasing the percentages of palmitic and stearic FA. This may seem obvious to you soap wizards, but I feel like a light bulb just came on (unless you tell me that I’m off track, of course)

 

[cmzaha]

Mine average 31-35 Stearic/Palmitic these are my tallow/lard, palm/lard, and palm/shea which is my vegan soap with 46% palm oil recipes.

 

[Mobjack Bay]

Mine average 31-35 Stearic/Palmitic these are my tallow/lard, palm/lard, and palm/shea which is my vegan soap with 46% palm oil recipes.

So maybe I’m not so far off. Do you put vinegar in those soaps? I think I remember that you put vinegar in all of your soaps. Thanks.

 

[DeeAnna]

You can build the stearic and palmitic FA content high enough that the soap becomes too insoluble. It won't lather much if at all or it will take a LOT of work to build the lather. And the lather, once built, tends to not rinse off the skin well, so there is a residue left on the skin that can be drying and irritating.

Shave soap borders on the edge of being too insoluble, which is why it takes a brush and a dab of patience to build a good lather, even with a nice shave soap.

If you make a shave soap with zero "bubbly" fats, so the soap is mostly stearic-palmitic-oleic, it's not very nice as a shave soap -- hard to create much lather and the lather, when you get it, is almost leathery or plastic-y. It would be a horrible bath soap. (Don't ask me how I know this.)

There's a balance to find between all the properties that make soap nice to use -- you can't focus on one property because you'll end up short-changing the others.

 

[MarnieSoapien]

The soap calcs use the % of palmitic + stearic + myristic + lauric to estimate hardness. That's basically a measure of hardness shortly after the soap is made to give the soap maker some idea of how quickly a soap can be removed from the mold.

I had no idea that hardness was referring to the time you could remove your soap from the mold. Thank you for that explanation!

 

[DeeAnna]

Saturated fatty acids from fats such as palm kernel, coconut oil, palm, lard, tallow, and the butters tend to make a bar soap that is firmer faster so it can be removed from the mold sooner. Unsaturated fatty acids, especially the polyunsaturated ones, tend to make a soap that stays softer longer, so it usually needs to stay in the mold longer. Any soap with any combination of fatty acids can get quite firm as it cures.

Remember the "hardness" number is based only on the fatty acids in the soap. If you change the water content, saponification temperature, superfat, or other soap making parameters, the soap might not be as hard or as soft as you might expect just by looking at the "hardness" number.

For example, a soap that doesn't get warm enough during saponification might stay softer than the hardness number predicts. Or a soap with a lot less water than usual might be firmer than soap made with a more typical amount of water.

 

[cmzaha]

I do use vinegar in almost all my soaps and I also use NaOH/KOH at 95/5% to help my bars lather faster. It really helps my bars in which I use the higher palm ie my vegan bars with 46% palm oil. All my bars lather very well and last approx 30 showers depending on how the bar is taken care of. The vinegar allows me to de-mold in 8-10 hrs and does not interfere with lather. If I want a milk soap I use powdered milks. I usually use vinegar at 50% since I like to masterbatch my lye.

 

[Dawni]

I tried upping those numbers in some of my current formulas for experimentation's sake and I was getting nowhere near 40 in any of them without sacrificing the other numbers that I like lol

I haven't tried with all my recipes though hehehe

My current ones are around 31-36 average, the highest being the ones that contain both lard and also a small amount of butters. I don't have access to palm and pure soy wax.

 

[DeeAnna]

My current favorite recipes are 29-33% palmitic + stearic.

 

[Mobjack Bay]

Surprisingly few of the many recipes I’ve tried to date have more than 30% palmitic & stearic. The ones that are >30% have been palm based and all moved fast even if I started at emulsion. I would like to formulate a palm-based recipe that has a higher longevity number, but I have a major fear of soap on a stick . I’ve been starting the palm-rich recipes mostly at around 105-110 (initial batter temp) to avoid stearic/palmitic spots, but in reviewing my notes I found that I made a successful batch using palm + shea (palmitic & stearic was 29%) where I started at 100 F. I almost always use 33% lye concentration (except for my HW:LW soap), and the soaps made in loaf molds have all gone through gel phase. I guess I can try upping the palm a bit with a starting temp of 100 F. I’m also wondering if hand mixing or mostly hand mixing would be helpful.

@Dawni I haven’t tried any recipes that have butters added to lard. Do you like the ones you’ve made?

As far as I can tell, no one seems to think that tempering the higher melting point fats helps with stearic/palmitic spots in soap but I wonder why that is. It seems to me that holding the fats slightly above the melting point for a bit would help to ensure that even the finest crystals are fully melted.

 

[Dawni]

@Dawni I haven’t tried any recipes that have butters added to lard. Do you like the ones you’ve made?

Yes

Two of my soaps have lard at 28% and both cocoa and shea at 10% each. One is my current best seller.... Although I only sell two soaps lol

The other is a beer soap that I'm currently thinking of adding as my 3rd one for sale. The difference, other than additives, is the beer one uses more RBO and less almond, and the other one's amounts are reversed.

The soap my son has been using for about half a year now has lard at 22% and also the same 10% of both butters. That has neem too, to up the longevity. My sister only uses that one when she comes over.

My high lard soap does well in terms of longevity without any butters but that's got 60% lard. I'll say it's my second hardest bar, the first being my extra rice soap. I can't say the lather is better or not as good, it's just different.

 

[Mobjack Bay]

A lard test bar I made for Szaza at 80% lard and 20% CO does not seem super hard to me, but maybe that’s due to the amount of CO. It’s a nice bar of soap, and enough so that it had me asking myself why I spent so much time formulating a lard recipe the first time I used it.

 

[Ladka]

The lard test bars I made for Szaza had the same ingredients in the same amounts. I find them fairly hard which I like but perhaps a bit drying to the skin - I attributed this to high coconut oil content.

 

[Mobjack Bay]

The lard test bars I made for Szaza had the sameingredients in the same amounts. I finf them fairly hard which I like but perhaps a bit drying to the skin- I attributed this to high coconut oil content.

Compared to my other high lard soaps, which have a max of 60% lard (except one 100% batch), they are way more bubbly at 20% vs. my normal 15% CO plus 5% castor. I keep trying to convince myself that they’re noticeably more drying, but so far I’m not convinced.

 

[DMCC]

I do use vinegar in almost all my soaps and I also use NaOH/KOH at 95/5% to help my bars lather faster. It really helps my bars in which I use the higher palm ie my vegan bars with 46% palm oil. All my bars lather very well and last approx 30 showers depending on how the bar is taken care of. The vinegar allows me to de-mold in 8-10 hrs and .

.

Do you also adjust your amount of lye because you’re using vinegar?

 

[Mobjack Bay]

.

Do you also adjust your amount of lye because you’re using vinegar?

Yes, See info here: https://classicbells.com/soap/aceticAcid.asp