two bars of hot process soap

Using Hot Process Soapmaking for Production Soaping

guest contributors soap science and info

This article comes to you courtesy of Molly.

Like many of you, I learned how to make soap using the cold process method. My soap story actually started with a large jar of coconut oil that I wanted to find a use for, and after a google search of "uses for coconut oil" learned that it is a wonderful oil to use in soap.

Needless to say, I found Soap Queen TV and never looked back.

After a few batches of basic cold process soaps, I wanted to step it up and learn to swirl and play around with various fragrances. And this is where I met my first set of soapy frustrations: a column pour with 5 colors that morphed into different colors, plus a disaster with an accelerating lilac fragrance oil that destroyed my plans for a wonderful butterfly swirl.

In my research, I came across a method of soapmaking called hot process. Hot process soapmaking sounded fun but looked oh-so rustic, which was not what I wanted to do.  I gave it a try anyway.

Here we are, several hundred batches of hot process soap later! I am here to tell you that if you think hot process soaps must be "rustic" like I did, you are mistaken. Many soapmakers are creating colorful, swirly and gorgeous hot process soaps.

(The soaps I have shown in this article are my own, simply because I have the rights to my own work!  There are, however, a slew of other hot process soapmakers out there creating far more stunning soaps.)

Hot process soapmaking is on a roll in the soapmaking world, and many soapmakers are rocking out this method. There is a huge list of benefits to hot process soapmaking, but what makes it's even better is that it is a fantastic method of soapmaking for large batch production!

 Ridgeway Soapworks Beer Hot Process Soap

Before I dive into what makes hot process soapmaking awesome for production, I would like to clarify what I mean by hot process soapmaking. The hot process soapmaking method uses heat to cook the soap, or in other words, to accelerate the saponification process. If you make cold process soap and insulate your soap to force the soaps to gel, you are mimicking hot process soapmaking but it is much slower than hot process and has a cooler temperature overall. The chemical reaction between oils and lye that creates soap is exothermic, meaning it creates heat. However, when you add an external heat source to the mix, the saponification timeline is sped up.

You may be wondering at this point who is writing this and why. I'm Molly, and I am not an expert in hot process soapmaking. I actually am not a fan of the word "expert" at all because we are all students (of soapmaking in this case.) Some of us are just a little bit further along in our education than others! I will never be done learning about soapmaking for as long as it remains a passion and my business! I do, however, love to make soap, love to research & learn, and love to write about soapmaking. That is why I am here: to share what I have learned about hot process soapmaking with all of you!

Benefits of Hot Process Soapmaking for Production

So, let's get back to business: what are the benefits of HP and why should production soapers pay attention?

Hot process soaps require a shorter cure time.

Faster curing is a benefit that many people are aware of when it comes to hot process soapmaking. Hot process soaps are fully saponified before they go into the mold, but they need time to harden up before packaging. The amount of time varies based on how much water you use in your formulas. I find that two full weeks of curing for my hot process soaps is plenty. (I use a 35% lye solution.)

That is a lot less time than the normal cold process cure time of four to six weeks! My wholesale clients love the shorter wait time when I need to whip up a new batch. Plus, if you create single color hot process soap (i.e. no swirls), you can water discount further and have your soap ready to package in less than a week!

Hot process soapmakers get to ditch their ricing and acceleration worries due to fragrance.

This one is HUGE for me! I love to try new fragrances and hot process soapmakers really luck out in this regard. For hot process soapmaking, it does not matter if a fragrance causes issues in cold process soapmaking! Why? In hot process soapmaking, the fragrance is added to the soap once it's already saponified! Every fragrance acts exactly the same in hot process: hoorah!

Hot process soapmaking allow you to choose your superfat oil/butter.

In cold process soapmaking, the lye is an equal opportunity saponifier: the lye doesn't care what you want the superfat to be, it's going to choose for you. In hot process soapmaking, you can add specific superfat oils after the soap is fully saponified!

I like to add my favorite skin loving oil to my hot process soaps, and doing so allows a particular oil to remain in its natural form and not be changed by saponification. Being able to do this is also great for label appeal. My favorite oils (which are usually butters) to add after the cook as my superfat are shea butter, cocoa butter and mango butter. However, you can add any oil that you like as your superfat! I actually add a whole bunch of goodies after the cook - goat milk, clay, colloidal oatmeal and yogurt.

 A Ridgeway Soapworks Hot Process Bar Featuring a Beautiful Swirl - it can be done!

Hot process soaps are less prone to colorant morphing.

Some cosmetic micas and natural colorants can change in cold process soapmaking due to the high pH level. Some colorants drastically change, while others fade or disappear. In hot process soapmaking, you add your colorants after the cook so they skip out on saponification and don't tend to change!

Cleaning up after a hot process soapmaking session is a cakewalk.

Cleaning up after hot process soapmaking is a dream compared to cold process soapmaking. I take everything I used, put it in the largest container I used, and let it soak for 15 minutes. Drain, rinse and repeat! No oily residue to clean off like with cold process soap, because the hot process soap is fully saponified! Time is money in production soaping and a fast clean-up is efficient!

Limitations of Hot Process Soapmaking

Now, no method is perfect, and hot process soapmaking does have its drawbacks! I still do a little cold process soapmaking every now and then for the some soaps. However, that does not mean everyone has to, but I have found that cold process soapmaking is more consistently reliable in some situations.

 A soleseife soap made with the cold process method of soapmaking

Struggles with Hot Process Soapmaking Salt Bars & Soleseife

I know a few soapmakers who make great salt bars with the hot process method, but I have only had struggles here. If you are not familiar with soleseife, it is a technique of using salt water as your lye water (either ocean water or by mixing salt into water yourself). Soleseife soaps are rock hard and have a wonderful lather.

Salt bars refers to handmade soaps where you add a fair quantity of salt to your raw soap batter. When I have tried to make hot process soap with a high salt content, the soap got very hard quickly and I had difficulty molding the soap in a loaf mold.

 A cold process soap made in a detailed individual mold

Struggles with Hot Process Soapmaking in Intricate Detailed Molds

Using detailed molds like the one in the photo above require a very fluid soap batter so that each little nook & cranny fills with soap. This can be quite difficult to do with hot process soap. I have tried to use detailed silicone molds for hot process many times, and while the soaps came out okay, I still prefer to use the cold process method for these types of soaps.

Limitations with Hot Process Soapmaking and Batch Size

With hot process soapmaking, just like cold process soapmaking, you will be limited in your batch size based on the container you use. However, in hot process soapmaking, the container needs to be able to be heated!

If you make hot process soap in a crockpot, you will be limited by the size of your crockpot and/or how many crockpots you have. However, there are large turkey roaster crock pots that can be used. The downfall is that they are expensive, and you will again be limited to how big they are and how many you have.

Hot process soap can be made in other types of pots though. I personally use a large steel lobster pot! As I continue to make larger batches of hot process soap, I can purchase bigger pots. The limit for me will be how heavy of a batch I can make and lift, which is also a challenge in production soaping using the cold process method.

So, let's recap on why hot process soapmaking is great for production soaping: you can turn hot process soaps around quickly, you get extremely predictable results when using fragrance and colors, and your expensive luxury oils (or other additives) retain their skin-loving properties by avoiding saponification.

Next up, I'll dive into the various methods of hot process soapmaking, the benefits of each method, which methods are best for big batch production soapmaking, and what I recommend starting with if you have not done hot process yet!

Have some hot process soapmaking goodness you want to see? Leave me a comment below and let me know what you'd love to learn about hot process soapmaking!

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