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Soap Challenge Club October 2020- Ghost Swirl

The Soap Challenge Club, hosted by Amy Warden, is a group of soap makers who come together to learn new techniques and engage in a little healthy competition each month. Amy shares a tutorial and soap makers have the month to practice the technique, ask questions, share tips, and finally enter a soap for competition. For October, the challenge was to create a "ghost swirl" soap. Clara Lindberg of Auntie Clara’s developed the technique we know as the ghost swirl in 2015.

This technique creates subtle differences in opacity of soap only by manipulating the water content of different portions of the soap batter. This difference in water content controls whether or not a soap will go through "gel phase". The reaction that produces soap is exothermic. Remember that term from high school chemistry? That means a chemical reaction produces heat. So when you pour your soap batter into your mold and then put your hand on the side of the mold a couple hours later, it will be warm or even a little hot to the touch. Gel phase occurs when the soap batter reaches about 180 degrees Fahrenheit causing it to take on a gelatinous appearance. This gelatinous appearance is only temporary, and the soap will perform the same whether or not it went through this gel phase. However, the color of the final soap bar will be a little different. Soaps that went through gel phase will appear more opaque and vivid in color. Many soap makers insulate their soaps to encourage uniform gel phase. Or they may put soaps in the refrigerator to discourage it, such as in the case of milk soaps where the sugars in the milk can scorch if the soap heats up too much.

Water content affects how easily a soap will go through gel phase. A lower water content soap will have to reach higher temperatures in order to gel. Therefore, if you mix soap batters with fairly different water contents as the only difference between them, you can get a subtle difference in the appearance of the soap. Ideally, the higher water content will have gone through gel phase taking on a more opaque appearance. In contrast, the lower water batter will not have reached gel phase and will remain less white, or less opaque. Hence the "ghost swirl". 

In a ghost swirl soap, there is no specific way to swirl the soap; it's at the soap makers discretion. This was the case for the October challenge for the Soap Challenge Club. The rules for the advanced category were that soap batters at different water concentrations are to be mixed or swirled together with no additives or colorants used. The only difference between the soap batters being used would be the water content. The different batters should also come from the same masterbatched oils and not prepared separately.

I had not attempted the ghost swirl prior to this challenge; however, I was quite eager to do so. I was interested in the technique since it's a manipulation of the chemistry of soap making to create design, and I am a certified science geek. (Not sure if there really is a "certification" for science geek, but I'm sure I would qualify.) Soap making appeals to me because it is the perfect amalgam of chemistry and art. I am grateful to the Soap Challenge Club for providing me an opportunity to learn the ghost swirl.

I attempted the ghost swirl twice. Both times I used two different batters with different water contents. I prepared my oils, added a little lavender essential oil to the them, then divided the oils in half. I had prepared two different lye solutions. One was a 45% lye solution (55% water, low water), and the second was a 30% lye solution (70% water, high water). This was done by using the same amount of lye and just changing the amount of water that was used to dissolve it. I did add an equal amount of sodium lactate to each cooled lye solution to help in unmolding, but that was it. No other color or additive was used.

Ghost swirl prep

If I were to use my scientific method here, I hypothesize that my low water batter would not go through gel phase and would not look as opaque as my higher water soap batter, creating the subtle ghost swirl. I also hypothesize that my lower water batter would trace, or turn into soap, faster.

In my first attempt, I did create a ghost swirl soap, just not a very interesting one. My hypothesis about the lower water content soap batter tracing faster was correct. I barely stick blended it and it was decidedly thick. I tried to "catch up" my higher water batter by stick blending a lot, but it remained much thinner. I attempted a hanger/butterfly swirl, but the low water soap batter was so thick that I didn't get much swirling. Also, my hanger swirl tool was really too thin to move thicker soap batter. I placed my mold (a wooden mold with silicon liner) on a heating pad on low setting for two hours and insulated the mold with a few layers of towels. After the two hours, I turned off the heating pad, but left the soap to sit insulated in towels overnight. This is to encourage uniform gel phase. A picture of my first attempt is below. You can see the subtle differences in the soap batter, but it just looks like "blobs" and not interesting swirls.

ghost swirl


My second attempt was done the same as my first, except I focused on trying to keep my low water soap batter thinner and pouring the two batters at thinner and similar consistencies. I did a much better job at this. I pulsed the low water batter once or twice and blended the "you know what" out of the higher water batter. They were both at a light-medium trace when poured. The low water batter was still a little thicker, but they were much closer in consistency. I decided to attempt a tiger stripe pour, alternating batters to create uneven, imperfect layers. I did put a twist on this though. I placed a large straw on my hanger swirl tool and placed it in the center at the bottom of my mold before I started pouring. I poured batters on top of the hanger swirl tool, alternating the high and low water amounts. Once I poured all the batter into the mold, I pulled the hanger tool straight up and out of the mold. This drew the layers upward in the middle. The straw on the hanger tool made it wider and better at moving thicker batter. This created a design that reminded me of the ribs of a skeleton. This was not intended, but a pleasant surprise for the October Soap Challenge! Once again, I used a heating pad and towels to encourage gel phase.

My second attempt was also successful at creating a ghost swirl and was a little more interesting in design. My hypotheses proved to be correct in that the higher water batter reached gel phase and looked whiter and more opaque than the lower water batter. When I have the time to try this again, I would work a little harder at keeping the low water soap batter thinner so I could attempt a more intricate swirl technique. I also would like to see if the oven process method produces a different result. The oven process method uses heating an oven to its lowest temperature, placing soap inside, then turning off oven and leaving soap overnight. This would replace the heating pad/towel method to encourage a full gel phase. I enjoyed working on the ghost swirl and October is the perfect month to do it. Thank you Amy and the Soap Challenge Club!

Ghost swirl


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1 comment

  • Hooray for science!!! What a great post and fascinating results! Very ironic and appropriate rib cage design for sure! I think the CPOP method might give more contrast, but I can’t be certain. Hope you’ll try it to find out! :)

    Amy Warden

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