Crackle explained!!!

Many of us have asked about the dreaded crackle look - at long last I came across this article with an explanation! Mystery solved!!

http://thenovastudio.blogspot.com/2013/06/hot-stuff-explaining-crackled-soap.html

I've always liked the visual interest. I know it bothers some people but not me.

thanks so much for sharing! it has always baffled me why some batches do this...I always thought it had to do with titanium dioxide (white pigment.) well, another soap mystery solved!

I am skeptical of the "glycerin in veins" theory. Glycerin is a liquid at room temperature. If this theory is correct, then glycerin "rivers" in the soap would be runny, wet channels, not clear trails of firm soap.

The old soap makers (1800s to early 1900s) made mottled soaps that were popular with the customers of the day. They would add a coloring agent to a finished soap, pour the soap into "frames" (large molds), and carefully control the rate of cooling. The soap molecules formed from short-chain fatty acids (palmitic, lauric, myristic, and stearic) would solidify into pale-colored "islands" first, essentially concentrating the color into the remaining fluid oleic and linoleic soaps. When the oleic and linoleic soaps solidified at a cooler temperature, they formed "rivers" of darker color around the "islands". The size and appearance of the mottles were controlled by the oils in the recipe, the way the finished soap was handled, and the rate of cooling of the soap in the frames.

The old makers used dyes to make the "rivers" dark colored and the "islands" lighter. Titanium dioxide is a ground pigment, not a dye, so it will concentrate differently if used in a soap -- it obviously is trapped within the "islands" not the "rivers".

"...When [soap] is permitted to cool rapidly the colouring matter remains uniformly disseminated throughout the mass; but when means are taken to cause the soap to cool and solidify slowly a segregation takes place: the stearate and palmitate form a semicrystalline solid, while the oleate, solidifying more slowly, comes by itself into translucent veins, in which the greater part of the coloured matter is drawn. In this way curd, mottled or marbled soap is formed..." Source: http://www.1911encyclopedia.org/Soap

Related thread: http://www.soapmakingforum.com/showthread.php?t=35815

it is a beautiful mystery , now explained. i still find it to be very lovely and somewhat artistic look to soap.

I truly love how it adds character to a soap!

DeeAnna, so this would mean that any soap that is gelled or not cooled in the fridge/freezer will show mottling because it is cooled while pouring then will solidify slowly? Or only show if colorants are added which can highlight or make the mottling apparent? Or is it thought to happen more often when your soap is high in stearate and/or palmitate oils? I don't mind it, in fact I think sometimes it can add to the beauty of a soap.

I certainly don't have definitive answers, Kazmi, but I am hearing two recurring themes when experienced soapers talk about crackle.

One theme is that obvious crackle seems to be strongly related to using titanium dioxide. I don't know if TD just makes the crackle more obvious or if it can actually trigger crackle in recipes that might not crackle without TD. Some of this connection of TD with crackle might be that folks are putting TD in their soap batter before it is fully wetted. Several people say they mix TD in water, glycerin, or oil and let the mixture stand for awhile, even overnight, before using it. Oil-soluble TD versus water-soluble TD might also be a factor, but I'm not sure which might be less prone to crackle.

Someone commented that there was very little talk about crackle just a few years ago, and the commenter thought this issue is discussed a lot more now. I wonder if perhaps that's because people are using TD more often now to make the fancy swirled and brightly colored soaps? I don't have a way to know that, but it seems like a possibility. Maybe someone who has been soaping longer than I have can comment.

Another theme is that crackle is more common in soaps made with palm oil, which can have a high stearic fatty acid content if it is not well mixed before use. Some thoughts people have about using recipes with large amounts of palm include:

mix the palm thoroughly before measuring it to ensure the oil is consistent
keep the batter temperature warmer -- 110-115 deg F (43-46 C) -- rather than soap at room temperature
reduce the palm content if crackle is a persistent problem (one person was getting crackle with a recipe that had 70% palm and eliminated crackle by going to a 40% palm content)
use as strong a lye solution as is reasonable, rather than stick with "full water"
and, yes, another suggestion was to avoid gel

Just my thoughts and observations -- I'll be curious to see what you all think. I rather like soap with crackle/stearic spots/TD streaks/snail trails/mottles or whatever you want to call it.

As a side note, I've had the dreaded crackle but I don't use Palm or TD!
It's happened in my bars with ultramarines and in some other bars here and there from time to time.

DeeAnna said:

Someone commented that there was very little talk about crackle just a few years ago, and the commenter thought this issue is discussed a lot more now. I wonder if perhaps that's because people are using TD more often now to make the fancy swirled and brightly colored soaps? I don't have a way to know that, but it seems like a possibility. Maybe someone who has been soaping longer than I have can comment.

Click to expand...

:wink: I think you're spot on. Also, hardly anyone used CPOP.

Lady M -- I think crackle can happen in any soap formulation, given the right conditions of cooling and ideally the use of a colorant (your ultramarines, for example). Just that TD and palm seem to increase the probability of crackle in current-day soaps. The old guys I quoted in an earlier post in this thread didn't use TD nor did they use a lot, if any, palm. Their soaps were often tallow and coconut based due to cost and availability.

I agree - palm + TD can be a crackle nightmare

Interesting DeeAnna! I'm a newbie at this and have a lot to learn. If I use palm it's usually no more than 10-20%, I typically avoid gell, and haven't used a lot of colorants/TD yet so I haven't experienced crackle. But I have noticed a difference in texture of my soap when I use palm and gell it. That's probably related to the stearate and palmitate solidifying at different rates than the rest of the oils. So much to learn!!

kazmi said:

Interesting DeeAnna! I'm a newbie at this and have a lot to learn. If I use palm it's usually no more than 10-20%, I typically avoid gell, and haven't used a lot of colorants/TD yet so I haven't experienced crackle. But I have noticed a difference in texture of my soap when I use palm and gell it. That's probably related to the stearate and palmitate solidifying at different rates than the rest of the oils. So much to learn!!

Click to expand...

:wtf: sooooo many recipes, yet so little time--LOL! I just go ahead and embrace the crackle, the ash, the discoloration, the odd shaped bars and what-have-you...it still beats anything from the store, and it definitely looks handmade!

I noticed I only get crackle when I use TD mixed with water and occasionally with ultramarine violet. Definitely occurs more often when I gel but not all of the time. I always use palm. Interesting info!

That was interesting, but I have never had a crackle effect unless I use TD..