Soap is heating up without any apparent reason

[Melonia]

Hello everyone. I crafted a soap using milk, but it burned and cracked, making it impossible to cut. Following this, I made a second batch and placed it in the freezer for 24 hours. However, three days into the curing process, the soap began looking darker, felt weak and dry, and overall was not pleasant. For the third batch, I opted to remove milk from the equation and instead used oatmeal and chamomile. Yet again, my soap began to heat up, exceeding 56 degrees Celsius, and started showing small cracks in the middle only 15 minutes after being placed in the mold. To remedy this, I immediately put it in the freezer.
HERE IS A BRIEF OF EVERY BATCH:
In the first batch, which used powdered milk but did not involve any freezing, the batch burned and cracked upon being demolded after 24 hours. It was so difficult to cut into pieces. The oils used in this batch were as follows:
Olive oil: 45%
Coconut oil: 25%
Palm oil: 25%
Castor oil: 5%
7% superfat
Sodium lactate was also added.
In the second batch, I again used powdered milk but this time put the soap in the freezer. Two or three days into curing, the soap began exhibiting a darker, drier appearance. The oil percentages remained consistent with the first batch, but I only added salt, omitting sodium lactate.

In the third batch, I didn’t use powdered milk but incorporated oatmeal and chamomile instead. This batch became extremely hot, but the percentage of oils used was unchanged. I did include sodium lactate this time.

I believe the oils play a crucial role in these outcomes. Previously, I had made a batch using oatmeal but with different oil percentages, and it didn’t overheat. Plus, the resulting soap was of good quality. The oil percentages were as follows:
Olive oil: 35%
Coconut oil: 30%
Palm oil: 30%
Castor oil: 5%
7% superfat
Both salt and sugar were included.


I’d appreciate any insights on what could be happening here.

 

[ScentimentallyYours]

Your oils look fine, ie not the cause of overheating. What percentage of water:lye did you use?

 

[Melonia]

I used 2.5:1

 

[Ford]

That's a lot of water for that recipe. Try lowering your water. 2.0:1 should be enough. For that recipe.

 

[Melonia]

but water doesn't cause overheating, I sometime use 2:1 it depends if I want to make different layers with different colors so I need more water to slow the trace.

 

[Mobjack Bay]

Are you using relatively fresh fats? Older fats may contain high percentages of free fatty acids that will cause the soap batter to accelerate. Past that, it will be difficult to identify factors that may be contributing to overheating without additional details. For the best troubleshooting, please provide your full recipe and information on your methods. What was the weight of each fat, the water and lye weights and the amount of milk powder and sodium lactate you used? What was the approx. temperature of the oils and lye solution just before you mixed them? Did you add a fragrance oil or essential oils? How did you add the milk powder? What do you mean by the soap felt weak? Can you post a photo of the soap?

 

[Melonia]

Are you using relatively fresh fats? Older fats may contain high percentages of free fatty acids that will cause the soap batter to accelerate. Past that, it will be difficult to identify factors that may be contributing to overheating without additional details. For the best troubleshooting, please provide your full recipe and information on your methods. What was the weight of each fat, the water and lye weights and the amount of milk powder and sodium lactate you used? What was the approx. temperature of the oils and lye solution just before you mixed them? Did you add a fragrance oil or essential oils? How did you add the milk powder? What do you mean by the soap felt weak? Can you post a photo of the soap?

yes I used fresh oils, my full recipe details is written in my post for every batch, the water lye rate as I mentioned 2.5:1, AND for the milk I used 5 tbsp. mixed with water and put it in the freezer to prepare ice cube for lye to mix, my oils was 1000 Grams and 20 Grams of sodium lactate, the temperature was at room temp 23 C. I used fragrance oil 20 Grams.
AND the overheating is only happening when I am using these percentages with or without milk:

Olive oil: 45%
Coconut oil: 25%
Palm oil: 25%
Castor oil: 5%
7% superfat

with these percentages, there isn't any overheating at all:

Olive oil: 35%
Coconut oil: 30%
Palm oil: 30%
Castor oil: 5%
7% superfat

Initially, I thought the mold might be the problem, but the same mold is used every time. And by the way, it’s a homemade mold made of cardboard and lined with parchment paper. Here’s a photo of the second batch of milk soap. It didn’t burn because I stored it in the freezer, but it did darken after a few days from unmolding and cutting. Moreover, the overall structure of the soap feels weak and prone to cracking:

 

[DeeAnna]

I highly doubt your problem comes from the slightly different proportions of the various fats in your recipe. If the fats are the issue, we'd be seeing this problem in a lot of people's soap, assuming you're using fats typical of the ones used worldwide by many soap makers.

The photos you provided in your last post show soap with extremely mottled coloring and irregular texture. I'd have guessed it was a soap made with a hot process method and the hot soap was packed into the mold with wetter and drier parts all mixed together. That can create a weak, crumbly structure.

I gather you used a cold process method, however, so it's possible this soap riced or otherwise saponified very quickly. That suggests there was some kind of accelerant in the the batch. Fragrance is often the culprit.

 

[Melonia]

I highly doubt your problem comes from the slightly different proportions of the various fats in your recipe. If the fats are the issue, we'd be seeing this problem in a lot of people's soap, assuming you're using fats typical of the ones used worldwide by many soap makers.

The photos you provided in your last post show soap with extremely mottled coloring and irregular texture. I'd have guessed it was a soap made with a hot process method and the hot soap was packed into the mold with wetter and drier parts all mixed together. That can create a weak, crumbly structure.

I gather you used a cold process method, however, so it's possible this soap riced or otherwise saponified very quickly. That suggests there was some kind of accelerant in the the batch. Fragrance is often the culprit.

Yes, I worked with the cold process. When I added the fragrance oil, I noticed some crumbles in the mixture. I used gardenia and vanilla fragrance oil. However, when I first removed the batch from the freezer, it didn’t have this appearance. It was matte, creamy, and had a nice color and texture. Yet, after a few days, it changed to a darker, crumbly, and weak structure, as shown in the photo.

 

[DeeAnna]

... I used gardenia and vanilla fragrance oil. ...

Floral fragrances tend to be accelerants. My guess is this one caused your soap to saponify extremely quickly. Hard to say without watching while you made the batch.

I'd be wary of this fragrance -- not every fragrance is suitable for use in soap making. Be sure to use fragrances tested in soap and read the supplier and customer reviews for any advice about how the fragrance behaves.

It doesn't matter how the soap looks at first when it's newly made. What's more important is how the soap turns out as it cures.

 

[Melonia]

Floral fragrances tend to be accelerants. My guess is this one caused your soap to saponify extremely quickly. Hard to say without watching while you made the batch.

I'd be wary of this fragrance -- not every fragrance is suitable for use in soap making. Be sure to use fragrances tested in soap and read the supplier and customer reviews for any advice about how the fragrance behaves.

It doesn't matter how the soap looks at first when it's newly made. What's more important is how the soap turns out as it cures.

Yesterday, I made salt bars using gardenia fragrance oil, The soap had firmed up nicely but with different oil percentages, I believe the mold may have played a role. My cardboard mold is deep, which might have retained too much heat, but again that only happened when oil percentages be like: Olive oil: 45% Coconut oil: 25% Palm oil: 25% castor oil 5%.

thank you, I will do more experiments with other molds and with deferent scents.

 

[ScentimentallyYours]

I believe the mold may have played a role. My cardboard mold is deep

How deep is the mold? I find this interesting because I used a Pringles can for a mold last month with a well tested recipe, and the soap got very and rose out of the can with a crack before settling most of the way back down. later I read that I needed to leave a full inch of room for expansion.

 

[Melonia]

How deep is the mold? I find this interesting because I used a Pringles can for a mold last month with a well tested recipe, and the soap got very and rose out of the can with a crack before settling most of the way back down. later I read that I needed to leave a full inch of room for expansion.

The depth is 11 cm and it has a thickness of 2 cm. I noticed a difference when I used a silicone cavity mold with the same fragrance oil and fats percentages. It didn’t heat up as much and there weren’t any cracks. Of course, the fragrance oil did play a role in accelerating trace a little, but overall the soap turned out fine.


I conclude that using a shallow silicone cavity mold may help to reduce heat. Although I have been using my cardboard mold without any issues, it appears that it was not suitable for making milk soap with a floral fragrance oil.


Please see the pictures below, The soap on the right was made using the cardboard mold, while the one on the left was made using the silicone mold, both milk soap was made using same recipe I mentioned " the second batch":