Soap cracking after cure

[Chispa]

Hello,

I have a hand soap that is cracking apart. It is three months old, and sees heavy use.

ingredients:
55% Coconut oil
37% Lard
5% Castor oil
3% lanolin

3% tea tree EO as fragrance
2% sugar
2% salt
2% Citric acid + extra lye to offset

1% superfat

What causes this kind of cracking, and how do I prevent it? I can see the same thing beginning to happen to the other bar of hand soap I have out.

The cracks are purple because the kids washed their hands after watercoloring.

 

[CaraBou]

Wow, that's cool! Let's figure it out!

I've never used lanolin but I know it's waxy. I'd guess the lanolin formed a distinct pattern as saponification occurred around it. I imagine that could happen if the batter wasn't warm enough to keep it melted and fully integrated into the batter. But that's just my best guess.

Other potential leads: Was it hot processed? Or perhaps a plop and swear? By the latter I mean did it accelerate or solidify quickly when you made it, such that you had to spoon it in the mold?

All of my questions relate to components of the batter solidifying at uneven rates, and then wearing down unevenly too.

I'm very interested - I think you and your boys just found a new design technique

 

[Millie]

Hey, this is exciting, I've never seen that in person or on any of the soapy troubleshooting blogs either. I'll stick around to see what everyone comes up with.

I'm voting for high coconut, along with low superfat, maybe salt and definitely frequent use contributing to this interesting effect. The first three leading to a brittle bar, the last adding stress. Plop CaraBou's idea in there too, something to stress over

 

[Chispa]

The lanolin is waxy, but not solid wax, more like a vaseline texture. The batter was reasonably warm to melt the coconut oil. The batter was clear not cloudy when I made it. I seem to remember the lanolin accelerating it quite quickly. I think it was at a very heavy trace. It was my third or fourth soap, and I wasnt taking as detailed notes back then. I CPOPed it at 65C for three hours.

The bar is very hard, and makes the most beautiful lather. It cleans the hands very well but doesn't seem to dry the skin out. I figure it is probably too strong to use on the rest of the body, but it is perfect for dirty hands. This cracking thing is the only real problem with it.

The cracks do not appear until the bar is used for a while.

 

[The Efficacious Gentleman]

Is the the location in the picture where the soap generally sits? Does it get a lot of use? How dry is the room? Is there an extractor or dehumidifier running?

I'm thinking maybe it is really quite wet from use but the outside is getting dried

 

[Chispa]

Is the the location in the picture where the soap generally sits? Does it get a lot of use? How dry is the room? Is there an extractor or dehumidifier running?

I'm thinking maybe it is really quite wet from use but the outside is getting dried

It's in the bathroom, it sits there on the side of the sink as shown in the picture. It gets used 10-15 times a day by kids who can barely remember to flush the toilet, much less respect the soap. The humidity in my part of the world is quite low, but it's a fairly busy bathroom which would raise the humidity a bit. The extractor is hardly ever run, no dehumidifier.

You might be on the money Craig.

 

[Susie]

Although I doubt it has anything to do with the cracking, your soap would benefit by having something under it that allows water to drain away like this:

https://www.ebay.com.au/itm/Silicon...hash=item25d487f6fd:m:mDapJQhKp61v5xtgJaDzJ8A

On a side note: I noticed that your Amazon was only books. I can't begin to express how sorry I am! I am completely addicted to our Amazon that has everything in it. It is my go-to source for hard to find items.

 

[Lion Of Judah]

Quick question Chispa : " How long did you cure your soap for ? " Some of the other opinions shared here I'm in agreement with as far as drainage and the use of a soap dish to help dry out the bar between use. I have never used lanolin so I'm not up on its characteristics in soap. The only thing that comes to my mind in watching the soap it that it may be something to do with curing time and quick use before full cure compounded with poor drainage of the soap.
That missing hexagon piece within the soap [ like it fell out ] seems to indicate the soap did not have one solid uniformity , like it was segmented , as you sometimes see in early HP soap making , as stated earlier hinting to "plop" or "spoon" filling the mold. All in all I'm interested in the answer or general consensus as to why it looks like this.

 

[DeeAnna]

Cracking like this is also seen in commercial soaps. It happens when the soap remains a little too damp for a little too long. While damp, the more water-soluble soap particles are able to absorb water and soften. The next time the bar is used, these softer bits wash out of the main body of the soap. Eventually a crack forms as more and more of the softened soap washes away.

In commercial soaps cracking happens more often around the sides and ends of the bar, and not so much on the larger faces, because of the way these soaps are mechanically mixed and then pressed or extruded into bars. In hand crafted soaps, the cracking can happen all over, but it's still the same general thing. Not every soap will crack like this. Whether a soap forms cracks or whether it wears away more evenly depends on the specific way the soap is being used as well as its general formulation.

Every bar of soap is a mixture of various types of soap molecules, and these molecules naturally want to organize themselves in certain ways. There are going to be natural "fault lines" where more of the water soluble soap particles are concentrated. These fault lines aren't always visible but they are always there to some degree. Cracking is a visible example of these fault lines, and they're also visible when soap shows obvious mottling and streaking (aka glycerin rivers). It's just a normal thing that soap does; sometimes we can see it and sometimes not.

An important part of the solution to the cracking is to use a soap dish, so the soap can drain well and also can dry out as much as possible between uses. You want the water to stay as much as possible on the outside of the soap -- you don't want the water to have lots of time to penetrate deeply into the soap.

If the bar is used as frequently as you say, a soap dish may not entirely solve this problem, but leaving any soap to sit in a puddle of water will always cause the soap to deteriorate quickly, regardless of whether the soap cracks or not.

Another thing that will help is to reformulate your recipe so the bar contains a higher percentage of soap that is not as soluble -- in other words, use more fats high in palmitic and stearic acids, such as palm, lard, or tallow. If you reversed the percentages of coconut and lard, for example, that would be helpful.

Remember too that cracking is a cosmetic fault, not a sign the soap is "bad."

 

[MorpheusPA]

I've had this happen as well, with a heavily water-discounted soap. The recipe for that was 50% coconut, 50% soy wax, and the last time I ever made that particular formula.

My unfounded assumption at the time was that the soy tore the structure apart as it set, and the coconut sure wasn't helping matters. Future soap substituted lard or tallow for the soy, and it's plenty hard enough.

In my case, it was just for at-home usage as gardener's soap and I mentally called it "Summer Pavement" and ran with it.

 

[Chispa]

Thanks for the clear explanation DeeAnna. It makes perfect sense to me. A soap dish will probably help with the problem, but probably not solve it.

Another thing that will help is to reformulate your recipe so the bar contains a higher percentage of soap that is not as soluble -- in other words, use more fats high in palmitic and stearic acids, such as palm, lard, or tallow. If you reversed the percentages of coconut and lard, for example, that would be helpful.

I'll try swapping the lard out for tallow, and use a larger proportion of tallow for a more durable bar.

 

[Susie]

You can keep using lard. It is the high amount of coconut oil that she is referring to. Tallow and lard used together is my favorite. Tallow for bigger bubbles and extra hardness, lard for that lovely dense lather.

"ingredients:
55% Coconut oil
37% Lard
5% Castor oil
3% lanolin"

Should read more like:

Lard and/or Tallow 55-80%
Coconut Oil 15-20%
Castor Oil 5%
Lanolin 3%

 

[DeeAnna]

I don't see a huge difference between tallow and lard as far as adding longevity to the soap. Tallow tends to make a harder bar -- brittle even. But physical hardness is not the same thing as durability/longevity, and I know people often confuse the two.

Like Susie says, a blend of both is nice, but I prefer the lard to dominate. My latest recipe contains both at 3 parts lard to 1 part tallow to give an idea of the proportions. If I had to pick only one to use, I'd pick lard over tallow.

 

[Chispa]

I don't see a huge difference between tallow and lard as far as adding longevity to the soap. Tallow tends to make a harder bar -- brittle even. But physical hardness is not the same thing as durability/longevity, and I know people often confuse the two.

With tallow having much more stearic acid than lard, I would not have suspected lard of having better longevity. That's very interesting!

 

[DeeAnna]

"...With tallow having much more stearic acid than lard, I would not have suspected lard of having better longevity...."

I didn't intend for you to take my comments as saying lard makes a longer lived soap than tallow. That was poor writing on my part. I was thinking more about soap in general and people in general when I said that physical hardness is often confused with longevity.

IMO, the total % of palmitic and stearic acids is a good measure of the durability or longevity of a bar, not just stearic alone.

I agree that tallow has more stearic + palmitic than lard does, and I agree that a high or all tallow bar is definitely hard and long lasting. But there's such a thing as too much of a good thing. In my experience, soap with a high % of tallow is too insoluble and too hard. A high tallow bar of soap can be brittle and thus difficult to cut. As Susie pointed out, the lather of a high tallow soap is also not as abundant and pleasant, compared to lard.

I hope this clears up the confusion I've caused.

 

[Chispa]

"
IMO, the total % of palmitic and stearic acids is a good measure of the durability or longevity of a bar, not just stearic alone.

I agree that tallow has more stearic + palmitic than lard does, and I agree that a high or all tallow bar is definitely hard and long lasting. But there's such a thing as too much of a good thing. In my experience, soap with a high % of tallow is too insoluble and too hard. A high tallow bar of soap can be brittle and thus difficult to cut. As Susie pointed out, the lather of a high tallow soap is also not as abundant and pleasant, compared to lard.

That makes perfect sense and jives well with what I understand about soap. Thanks for clearing that up!

 

[SaltedFig]

Just to add a little ... I believe that reducing the time and the temperature of the CPOP (perhaps even to no extra heat at all for this recipe) would also help.

And hi!

The lanolin is waxy, but not solid wax, more like a vaseline texture. The batter was reasonably warm to melt the coconut oil. The batter was clear not cloudy when I made it. I seem to remember the lanolin accelerating it quite quickly. I think it was at a very heavy trace. It was my third or fourth soap, and I wasnt taking as detailed notes back then. I CPOPed it at 65C for three hours.

 

[Totem Eco]

Hi Chispa,

Joining this thread very late but was interested to see your post as there appears to be little written about this cracking issue post saponification.

A lot of cracking forums/websites talk about the issues of cracking due to overheating etc during saponification but not after, or during the lengthy curing process.

We have also witnessed surface cracking almost identical to the photo you posted. In our case, this is not attributed to hard oils such as coconut or waxy components and is the result of environmental conditions during the curing process, more specifically - ambient temperature and climate control (in this case, the lack thereof).

Where are you curing your soaps and what sort of environment are they in? I see you're from Australia as are we As you know, our temperature and humidity differs greatly between summer and winter in the land of OZ and we find that winter is not our friend during the soap curing process.

If you have soap constantly exposed to significant temperature and humidity fluctuations as your soap dries out during the curing process, you will find that while invisible to the naked eye, your soap is also constantly expanding and contracting that ultimately leads to cracking. If you look closely during the curing process (2-3wks after pouring or longer), you'll see that the first signs of this issue - very faint hair-line cracks across the surface of the soap (more visible in natural light). Over time, these hair-line cracks will deepen and become clearly visible, just like the cracks in your photo. If you didn't see them before you started using your soap, the cracks were probably already there as hair-line fractures and simply but made more prominent upon use and with the addition of kid's water colours entering the cracks.

During winter in particular, the temperature of your house can plummet overnight and depending on where you're curing your soaps, daily temperature fluctuations can be significant. And if you're curing your soaps in a laundry space for example, you may also find that clothes' driers can greatly influence humidity which can also contribute to this issue.

If it sounds like this could be a contributing factor, we suggest you try and find a more controlled space for curing your precious soaps where you can maintain a more stable temperature and humidity during the curing process.

We'd love to know if these tips help and hopefully you're still enjoying the wonderful world of soap making

www.totemeco.com.au
Totem Eco. (@totem_eco) • Instagram photos and videos
Totem Eco