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Why do some recipes heat up and others don't?


PurpleHippie

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I've been testing several different recipes and noticed a difference in the geling stage. The past soaps have all been wraped with thick towels and placed in the same location. The room temp. there is around 79-81 degrees. All of the recipes I have tested this past week heat up pretty quickly and start to gel fast. The one I tried today only became slightly warm and didn't gel like the others. It's tucked in for the night so I won't know how the finished product will be until the morning. The only thing different about this recipe than the others is the addition of 5% Castor Oil and a different FO. What causes some recipes to heat up and gel quicker than others?

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Assuming the same batch size and mold, I think you're basically seeing differences in how fast the saponification goes. It can be affected by the amount of NaOH discount, the lye concentration and temperature of the mixture. Two of the biggest factors would be the oils you use and the fragrance.

Some oils saponify faster than others. The saturated fatty acids in harder oils speed things up. Polyunsaturated fatty acids in very soft oils slow things down. The ricinoleic in castor oil has unique properties that can speed up the reaction. Free fatty acids saponify very quickly and those could come from stearic acid you add to the recipe, or from oils with a higher acid content like olive pomace or anything that's going rancid.

Fragrance oils can have a huge impact. Some have very little effect and give you a leisurely soaping experience, while others give you very fast trace and possibly a hotter batch. I think the difference might have something to do with how the fragrance affects the emulsification of the mixture, sometimes facilitating the oil and NaOH coming into contact.

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Top's especially right about fos speeding things up. I used a green aloe and clover that instantly put the soap into a thick heavy trace. I used the stick blender to even it out and quickly poured it in the mold. You never know until you try it and see what happens. I soap at really cool temps (I guess) around 80 degrees and match my oils and lye water temps but depending on the formula; sometimes you may need to soap at a warmer temp. HTH.

Steve

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One more thing occurred to me.

Some of the things that affect the rate of saponification do so by affecting how easily the oil and lye solution are pulled into emulsion. The emulsification of the mixture (the process of bringing the oil and water together) is also controlled by the soaper.

All the mixing you do to achieve trace is about emulsifiying the ingredients to kick-start saponification. If you do less of it and pour at a thin trace, the whole process can go much slower. If you mix a lot and get it to a thicker trace, that will give it a bigger kick-start and you might get more accumulation of heat in the mold.

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All the mixing you do to achieve trace is about emulsifiying the ingredients to kick-start saponification. If you do less of it and pour at a thin trace, the whole process can go much slower. If you mix a lot and get it to a thicker trace, that will give it a bigger kick-start and you might get more accumulation of heat in the mold.

That is really interesting! I had not thought of that. I know when I do my 100% coconut salt bars (even without salt, if I do 100% coconut with high super fat), I get the batter quite thick so I can mix the salt in, and I have to take great care that it doesn't over heat.

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That is really interesting! I had not thought of that. I know when I do my 100% coconut salt bars (even without salt, if I do 100% coconut with high super fat), I get the batter quite thick so I can mix the salt in, and I have to take great care that it doesn't over heat.

I think all the saturated fatty acids in the coconut oil recipe would account for the fast trace.

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The rule of thumb that I learned off the Miller Soap site is that when your soap rises by 2 degrees its ready to pour. I watch my thermometer and wait for that 2 degree shift. If I pour past that climb in temp its usually a much thicker trace and is much more difficult to smooth out and remove air bubbles. Watch the next time you soap and see if that happens and then pour your soap. HTH.

Steve

Edited by chuck_35550
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One more thing occurred to me.

Some of the things that affect the rate of saponification do so by affecting how easily the oil and lye solution are pulled into emulsion. The emulsification of the mixture (the process of bringing the oil and water together) is also controlled by the soaper.

All the mixing you do to achieve trace is about emulsifiying the ingredients to kick-start saponification. If you do less of it and pour at a thin trace, the whole process can go much slower. If you mix a lot and get it to a thicker trace, that will give it a bigger kick-start and you might get more accumulation of heat in the mold.

That's exactly what I did with this recipe. The previous ones were mixed longer and poured at a thicker trace. I am experimenting with pouring thicker and thinner to practice swirling. I poured at a thin-med. trace. Thanks for adding that information Top!

Such good advice here. I appreciate everyone's help:)

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Hey, I could go on.

At the beginning I said, "Assuming the same batch size and mold." But that's a significant consideration too. Obviously some molds are better insulated than others, but also more heat gets trapped in larger batches than in smaller ones. The heat that's being generated throughout the batch has to escape from the surface of the soap, but as the batch gets larger the volume of soap increases faster than the surface area. That's especially true for block molds.

I make my production soap in block molds. My procedure includes some insurance to make sure the soap gels, but most batches probably would do so without any help. However, if I'm just trying out a formula in my 2-bar mini-mold, it have to keep it in an oven to make sure it gels. It would never warm up enough on its own. If I decided to use a mold twice the size of my normal ones, I'd have the opposite problem and would be worrying about overheating.

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