Question about the hardness of a soap bar

Hello!

I wanted to make a face-soap for myself. I read in a book that the hardness value of the soap calculator should be less than 34 but I do not really understand why. I developed the following recipe:

Olive Oil 47%, coconut 18%, castor oil 10%, soy wax 15% and avocado 10%, water concentration 25% and 10% of superfat. The hardness value was 39.

After 15 days of being in a mold I tried to unmolded. I found the soap bar quite soft and when I tried to cut it it got sticky to the knive and I left it to get drier. Is it because of the hardness value or because of the high percentage of superfat?

Does anyone have experience with soaps of low values of hardness.

Cheers

verotxu said:

Hello!

I wanted to make a face-soap for myself. I read in a book that the hardness value of the soap calculator should be less than 34 but I do not really understand why. I developed the following recipe:

Olive Oil 47%, coconut 18%, castor oil 10%, soy wax 15% and avocado 10%, water concentration 25% and 10% of superfat. The hardness value was 39.

After 15 days of being in a mold I tried to unmolded. I found the soap bar quite soft and when I tried to cut it it got sticky to the knive and I left it to get drier. Is it because of the hardness value or because of the high percentage of superfat?

Does anyone have experience with soaps of low values of hardness.

Cheers

Click to expand...

My guess is that it would be because of your high amount of soft oils and your high super fat. Also, if your lye concentration was 25% (I assume this is what you mean by "water concentration"), that would also contribute to your soft bar. If 25% is your water as a percent of oils concentration, that appears to give you ~33% lye concentration, which is good. If it was me, I'd increase the lye concentration to 33% at least, and either reduce your amount of olive oil or your superfat.

Why did you superfat at 10% with oils that likely already had your "conditioning" value through the roof?

Any particular reason for adding wax to your face soap?

Hi!

The concentration of lye was 33%. So I guess that it may be because of the high superfatting. I chose that value because I wanted to feel the effect of the avocado on my skin...which value would you recommend?

I added wax to have a contribution of hard fats....according to the calculator soy makse the bar harder and the lather creamy. I also wanted to check the effect of soy in soaps.

I use that % of water and 10% SF all the time and my soap isn't sticky.

I suspect that the combination of high OO, castor and soy wax is why your soap is sticky.

Did you gel?

Hardness, by the way, has to do with solubility (how quickly your soap dissolves) as opposed to how easy you can dent it with your finger. Castille soap is the classic illustration of this. When fully cured, it's like a brick. Drop it on you foot and it will hurt. But it will dissolve relatively more quickly in the presence of water than a 100% CO soap.

Give your soap a good long cure and see how it works for you. Also if you want the effects of avocado oil, you could make an oil serum and dab a bit on your face after cleansing.

I bet it is the soy wax. How about trying the same recipe with an oil instead of the soy wax.


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"...I wanted to feel the effect of the avocado on my skin..."

If you are making cold process soap, you will get a mixture of fats in the finished soap, not just the avocado. Upping the superfat in the typical soap recipe will only decrease your lather and make your soap softer -- it won't make the effect of the avocado oil more obvious.

It doesn't work to add an oil at trace with the hope that the lye will not react with it. If you specifically want the avocado to be the superfat, then you will want to make this recipe as a hot process soap and add the avocado when the cook is done and the soap is fully saponified.

"...I read in a book that the hardness value of the soap calculator should be less than 34..."

Did the author of this book give the reasoning behind this instruction? It seems rather odd.

18% castor oil is really high. In my recipes, I use it at either 1% or 3% and the soaps made at 3% are quite noticeably stickier longer. That's with percentages no where near yours. Not that lots of castor oil is bad or anything, your soap is just going to be stickier longer.

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Is it possible that was a typo and meant to say it shouldn't be below 34 for hardness? That would seem to make sense. You can add sodium lactate to your lye mixture which should help harden and I believe help with the stickiness. I can't remember the usage because I just use the cap on my bottle from Bramble Berry to measure mine.


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"...Is it possible that was a typo..."

Hard to say for sure without more info. But I wondered that too.

Hello!

many thanks for you comments!

I took the info of the hardness value from the "complete *****'s guide to Making natural soaps" by S.W. Trew and Z. B. Gould (page 44). The authors say that their facial bar have a hardness value of 34 or below.

Regarding the meaning of the hardness value, there a post debating about the meaning but unfortunately I am not able to find it..if I remember correctly they were commenting about the hardness meaning the softness of the soap bar when unmolding...

Cheers

Veronica

If it was me I would lower the castor to 5%, take out the soy wax and make up the amounts with palm oil and ignore the "numbers" on soap calc. Give it a good cure and try it out. It should be a nice bar of soap and just fine. Only by using the actual soap will you be able to know if it fits with your skin. Good luck

The "hardness" number in SoapCalc is the sum of the average amount of straight-chain fatty acids -- myristic, lauric, palmitic, and stearic -- in a soap recipe. It is a measure of the physical hardness of a soap after it's made ... hard like a brick vs. soft like clay.

As far as the water solubility -- the "melting" of soap in water -- well, the hardness number is not strictly a measure of water solubility. The reason is that the four fats included in the hardness number vary quite a bit in their solubility.

The shorter myristic and lauric fatty acids (found in coconut oil and palm kernel oil) make a soap harder and MORE soluble, all other things being equal. That's great if you want a soap that is a strong cleanser and lathers well in cold or hard water.

The longer palmitic and stearic (found in lard, palm, and tallow) make a soap harder and LESS soluble, all other things being equal. That's great if you want a soap that is milder and lasts longer, especially in warm or hot water.

So if you want a physically hard AND a less soluble soap, keep your hardness number fairly high (lauric + myristic + palmitic + stearic) AND keep your cleansing number (lauric + myristic) low. That means more tallow, palm, lard, etc. and less coconut, palm kernel, etc.

Water Solubility = SoapCalc Hardness - SoapCalc Cleansing
The bigger the solubility number, the LESS soluble the soap -- meaning the slower it will dissolve in water.

As far as what the author was getting at by keeping the hardness number below a certain value, I suspect she's trying to get you to formulate a recipe that is high in the monounsaturated and polyunsaturated fats (oleic, linoleic, and linolenic) and lower in the straight-chain saturated fats (lauric, myristic, palmitic, and stearic).

I guess I can see limiting the lauric and myristic, since these soaps can clean too well and sometimes irritate sensistive skin. But I don't entirely understand her goal of limiting palmitic and stearic. Lard, palm, and tallow make mild soaps that some people like for sensitive skin.

I agree with Sistrum -- less castor, omit the wax, add some palm (or tallow or lard if you are okay with animal fats), and try it.

Hi!

Many thanks for the explanation about the hardness parameter!

I will follow your advices and tell you the results. I am from Spain and it is not easy to get palm oil around here. I thought soy wax was a relatively inexpensive way of making the soap harder. It is way cheaper that cocoa butter or sheabutter.

Seems like soy wax is not very popular . Any reason for that?

Cheers

Soy wax is fully hydrogenated soybean oil. Waxes often melt at higher temperatures than the more common soap making fats. Beeswax melts about 150-160 deg F. The soy wax products I found melt at 110-180 deg F, depending on the product. Depending on the particular soy wax you use, its high melt point could make soaping a challenge, because you have to soap hotter and watch for "false trace".

The discussions I found about soy wax in soap is that it does add hardness, but reduces the lather. According to SoapCalc, soy wax is mostly stearic acid (87%) and palmitic acid (11%). These fatty acids will make soap physically harder, less water soluble, and have lower lather. Zen Soap did an experiment with single oil soaps. They evaluated a soy wax soap: http://www.zensoaps.com/singleoil.htm

If those properties are what you want to add to your soap recipe, there's nothing wrong with using it. A low lather soap doesn't seem like a good quality in a facial bar, however, which is why some of the posters on this thread might not be too enthusiastic about the soy wax. But if you like the qualities it adds to your soap, then you should use it.

Many thanks for your explanation!

I still need to learn a lot about the properties of the fatty acids.

Cheers!