Ugeauxgirl
Well-Known Member
I made a loaf of CP soap and just checked on it- seemed hot so I took it's temp with my heat gun. 140F. How hot does it have to get before it causes alien brains? In other words, should I uncover it or leave it alone?
How hot is too hot
- Thread starter Ugeauxgirl
- Start date
Help Support Soapmaking Forum:
Ugeauxgirl
Well-Known Member
After I posted that, the temp dropped to 130, and it's now at 110. Looks good. I still want to know, though. At what temperature should you uncover it to prevent cracking, alien brains, etc.
My question... At what temperature do you get the results you want. That is the correct temperature. Temperature is just a number. Not a written rule. Took me a while to get it thru my brain.
The recipe I use, would be in full gell. At that temp. And I would start cooling it down.
The recipe I use, would be in full gell. At that temp. And I would start cooling it down.
I've never thought to take the temperature of my soap while it's saponifying.
How hot a soap can get without developing alien brains is recipe dependent. I mostly make small batches using a high lye concentration and usually have to force gel by putting the mold on a heating pad or cpop’ing. Even though high lye concentration soap has to get quite hot to gel, I don’t get alien brains. Auntie Clara did a nice series of experiments to tease apart some of the factors that influence overheating and the development of alien brains in cpop’ed soaps: What's Hot and What's Not - A Study In Overheating
Ugeauxgirl
Well-Known Member
. I'll uncover it the next time it gets over 130.ETA- I don't have a set recipe. I guess a better question would have been, how hot does it need to get to fully gel
I have taken temps of saponifying soap a few times and found 140-150 F is a typical temp for the center of the loaf during active saponification. A temp in the 140-150 F range doesn't necessarily define whether the soap is overheating, however. It's not only the max temperature, but it's also the length of time the center of the soap is at that temp that determines whether the soap is going to show the effects of overheating or not.
I get good results simply by monitoring the appearance of the top of the loaf. If the center is beginning to swell upward, it's telling me it's on the edge of getting too hot and is likely to crack. When I see this swelling, I uncover the loaf if it's covered, set the mold in an area where there's good natural air circulation, and check it occasionally for another hour or so.
Many times that is all I need to do, but if I then start to see tiny cracks in the top -- or if the house is extra warm on a hot summer day -- I set the mold on a few food cans and aim a small fan at the mold to blow room air over it. That further increases the rate of heat transfer.
My soap has had a few cracks from time to time, but never alien brains or a volcano.
Ways to avoid overheating -- soap a bit cooler, reduce the lye concentration to raise the temp at which the soap gels, use a little less insulation, avoid CPOP (or use a lower temp CPOP method for a shorter time), and peek more often for that tell-tale swelling of the top.
I get good results simply by monitoring the appearance of the top of the loaf. If the center is beginning to swell upward, it's telling me it's on the edge of getting too hot and is likely to crack. When I see this swelling, I uncover the loaf if it's covered, set the mold in an area where there's good natural air circulation, and check it occasionally for another hour or so.
Many times that is all I need to do, but if I then start to see tiny cracks in the top -- or if the house is extra warm on a hot summer day -- I set the mold on a few food cans and aim a small fan at the mold to blow room air over it. That further increases the rate of heat transfer.
My soap has had a few cracks from time to time, but never alien brains or a volcano.
Ways to avoid overheating -- soap a bit cooler, reduce the lye concentration to raise the temp at which the soap gels, use a little less insulation, avoid CPOP (or use a lower temp CPOP method for a shorter time), and peek more often for that tell-tale swelling of the top.
Last edited:
The answer is pretty much the same - it's recipe and technique-dependent. This article by Kevin Dunn provides some of the answers:
To Gel or Not To Gel - Wholesale Supplies Plus
For a soap made with his recipe, starting with oils that are at about 100 F and using a 50% lye concentration (low water soap), the temperature of the soap in the mold reaches approximately 175 F within 45 minutes, but the soap does not gel (melt) because the melting point of the soap is higher (> 200 F). High water soap (25% lye concentration) made from his recipe melts at a lower temperature (approximately 145 F) and gel is achieved within about an hour if the starting temperature of the oils is at least 140 F. For his recipe, high water soap made with cool oils (100 F) will need external heat to force gel. The horizontal line on his charts for medium and high water soaps indicates the temperature required for the transition from solid to melted (gelled, "neat") soap. There's no transition temperature indicated on the chart for low water soap because they do not transition to gel. It's important to keep in mind that his recipe has no additives that cause heat generation, like honey or beer, and he does not add FOs, which may cause an otherwise well-behaved recipe to overheat.
From a practical standpoint, my best advice is to watch your soap until you get a good feel for how your recipe(s) behaves with and without additives and with different types of FOs. If you're using 33% or lower lye concentration you may or may not need to insulate the soap and it could take an hour or more for the soap to start to gel.
For my recipes and the methods I use, the soap usually won't gel unless I add heat and insulate. For example, for batches made in small test molds using 450-600 g of oil, recipe < 20% coconut oil, sugar added, 38% lye concentration, batter starting temperature of 90-100 F, and a non-heating FO, I put the mold on a heating pad set to high and also cover it with a blanket or thick towels. If it's not doing anything unexpected within the first 30 minutes, I leave everything as is and the soap will typically gel within two hours, which is when heating pad shuts off automatically. When I bought a new small slab mold last summer, this approach didn't work for my first batch, which gelled out to within 1/2" of the corners of the mold. For the next batch, I dropped the lye concentration a bit and the soap gelled all the way through. When I use beer or honey in the recipe instead of sugar, I may insulate the mold, but I probably won't need to add heat. When I make soap using my soy wax recipe, with a starting batter temperature > 120F, less external heat is needed to force the soap to gel. I haven't had many soaps overheat, but if I see the top getting puffy or it looks like it's going to crack, I put the mold on a rack and use a fan until it cools down.
DeeAnna posted just as I was getting ready to post this response.
To Gel or Not To Gel - Wholesale Supplies Plus
For a soap made with his recipe, starting with oils that are at about 100 F and using a 50% lye concentration (low water soap), the temperature of the soap in the mold reaches approximately 175 F within 45 minutes, but the soap does not gel (melt) because the melting point of the soap is higher (> 200 F). High water soap (25% lye concentration) made from his recipe melts at a lower temperature (approximately 145 F) and gel is achieved within about an hour if the starting temperature of the oils is at least 140 F. For his recipe, high water soap made with cool oils (100 F) will need external heat to force gel. The horizontal line on his charts for medium and high water soaps indicates the temperature required for the transition from solid to melted (gelled, "neat") soap. There's no transition temperature indicated on the chart for low water soap because they do not transition to gel. It's important to keep in mind that his recipe has no additives that cause heat generation, like honey or beer, and he does not add FOs, which may cause an otherwise well-behaved recipe to overheat.
From a practical standpoint, my best advice is to watch your soap until you get a good feel for how your recipe(s) behaves with and without additives and with different types of FOs. If you're using 33% or lower lye concentration you may or may not need to insulate the soap and it could take an hour or more for the soap to start to gel.
For my recipes and the methods I use, the soap usually won't gel unless I add heat and insulate. For example, for batches made in small test molds using 450-600 g of oil, recipe < 20% coconut oil, sugar added, 38% lye concentration, batter starting temperature of 90-100 F, and a non-heating FO, I put the mold on a heating pad set to high and also cover it with a blanket or thick towels. If it's not doing anything unexpected within the first 30 minutes, I leave everything as is and the soap will typically gel within two hours, which is when heating pad shuts off automatically. When I bought a new small slab mold last summer, this approach didn't work for my first batch, which gelled out to within 1/2" of the corners of the mold. For the next batch, I dropped the lye concentration a bit and the soap gelled all the way through. When I use beer or honey in the recipe instead of sugar, I may insulate the mold, but I probably won't need to add heat. When I make soap using my soy wax recipe, with a starting batter temperature > 120F, less external heat is needed to force the soap to gel. I haven't had many soaps overheat, but if I see the top getting puffy or it looks like it's going to crack, I put the mold on a rack and use a fan until it cools down.
DeeAnna posted just as I was getting ready to post this response.
Last edited:
140F sounds normal when you consider that CPOPing is done around 170F. I have 'baked' a soap. It was the second time I tried CPOP, forgot to turn the over off. Remembered about four hours later. I had 'silicone rash' on the outside and it was gelled, but no cracks (from expansion).
The first time I made Goat Milk Soap it overheated. I don't know for sure how hot it got, didn't have a digital thermometer at the time, but I figure it got up there since it was still a bit warm 18 hours later. It didn't crack, but it separated and it burned. It was this yucky brown color and it smelled and it dripped oil.
Also early in my soap days, I used the wrong Lye Solution. I was just so excited that it was the weekend and I got to make soap and so I grabbed the Lye Solution for 33oz of Oils instead of 14oz. I no sooner whizzed it into my Oils that it got so hot that I thought it was going to catch on fire!
Older advice about CPOP usually does suggest heating the oven to 170 F / 77 C and leaving the oven on while the soap was in the oven.
But a lot of people here on SMF have been recommending for quite some years now to heat the oven no higher than 140 F / 60 C and turn the oven off at the time the soap goes into the oven. All you need to do is heat the outer surface of the soap sufficiently warm and only for a fairly short time. The heat coming from the center of the loaf will finish the job.
I did a few CPOPs at 170 F when I first started making soap, but switched to the 140 F method not long afterwards from the SMF crowd, probably from Irish Lass who has been an advocate for this lower temp method for a long time.
But a lot of people here on SMF have been recommending for quite some years now to heat the oven no higher than 140 F / 60 C and turn the oven off at the time the soap goes into the oven. All you need to do is heat the outer surface of the soap sufficiently warm and only for a fairly short time. The heat coming from the center of the loaf will finish the job.
I did a few CPOPs at 170 F when I first started making soap, but switched to the 140 F method not long afterwards from the SMF crowd, probably from Irish Lass who has been an advocate for this lower temp method for a long time.
What I was hearing was 170F and turn off. My oven doesn't go that low...I have "warm" and then 200F.
Mine doesn't either. The work around --
Put a thermometer in the oven, turn the oven on at its lowest setting, and time how long it takes for the oven to warm to 140. Then you can warm the oven to the desired temp based on time, not the oven's thermostat.
My workaround: don't use the oven at all. Use a heating pad. 
Heating pads and heat blankets is what I use with my soap molds in low crates.
