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How I Started Making Big Batch Hot Process Soap

I love to hear stories from other soapmakers about how they started their businesses, and what the turning points were that made a big difference in their growth. So I thought I would share a little about my own experiences with my business!

I started out as a cold process soapmaker. After getting really frustrated with morphing colorants and fragrances that turned my fluid soap into an un-pourable solid, I gave hot process soapmaking a try.

For most of 2015, I was a happy, small batch, crockpot hot process soapmaker. I sold primarily online and at my local farmer’s market and when I ran low on a soap, I made another batch of ten bars. Life was simple! I had a few small wholesale accounts that would buy twenty¬†or so assorted bars at at time, usually selecting from my on-hand inventory.

My Jump into Big Batch Hot Process Soapmaking

When I got an order for 200 bars of Clean Cotton Soap, I eagerly took on the project. I calculated how many single loaf batches I would have to make to get this order done: twenty batches!

The thought of repeating the same exact batch twenty times was unappealing. Plus, my crockpot was only big enough for one batch!

It was time to make the jump to big batch hot process soap! I looked into buying a huge turkey roaster. Unfortunately, I didn’t have the space to store more big appliances, and the roasters are expensive.

Another soapmaker, Sharon Johnson, had recently written an ebook and posted videos about a different way to make hot process soap, using hot oils, hot lye solution, and constant mixing. With guidance from Sharon, I tried this method. The biggest benefit to me was that I could make hot process soap in any type of approved container. (Due to the high temperatures, stainless steel is the safest container to use.)

This method is not recommended for inexperienced hot process soapmakers, and a soapmaker should use extreme caution when using it. The temperatures and mixing often create a soap volcano, which can be dangerous if a soapmaker does not know what to expect or how to handle it. You have to be careful about your temperatures and you cannot leave the soap unattended. 

I bought a few more loaf molds that matched the one I was using a lot at the time. I started to make double batches instead of single batches. So, twenty batches became ten double batches, which was a lot less work! And it was exciting to be more efficient!

My first foray into bigger batches of hot process soap for an order of 200 bars!
My first foray into bigger batches of hot process soap for an order of 200 bars!

The following year, I started to pound the pavement to get more wholesale accounts. After a while, my hard work started to pay off.

Slowly, I picked up a few more accounts. At this point my larger wholesale accounts would order fifty to one hundred bars at a time. It was common for the orders to be for twenty bars each of five scents.¬†For the time being, I was content making double batches using my silicone molds and Sharon’s method.

And then it happened again!

I got an order that exceeded my experience level, this time for 400 bars of soap. It was time to really dive into big batch hot process soapmaking! I asked my husband to build me a few wooden slab molds; I got a log splitter (similar to this one) and a big stainless steel lobster pot. And I cranked through ten batches of forty bars in a few days, and delivered the order on time. Whew!

Big batch hot process soap making made 400 bars of soap easy!
Big batch hot process soap making made 400 bars of soap easy!

How I Make Big Batch Hot Process Soap Now

I still use Sharon’s method , coupled with¬†stainless steel lobster¬†pots¬†and a reliable stick blender. For me, this method gives me soap that is consistently fluid, which allows me to make swirled¬†hot process soaps.

What I’ve Learned About Big Batch Hot Process Soapmaking

A lot of these tips apply to making big batches of soap, no matter the method. But, some tips are specific to making big batch hot process soap:

Safe soapmaking¬†is more important than ever. A big batch of hot process soap coming in at¬†200¬į F (93¬į C) could severely burn you, both thermally and chemically depending on the stage of saponification. Know what to expect, how to handle it, and wear your safety gear. Exercise¬†caution: respect the ingredients and method. (Please!)

Like with cold process soapmaking, masterbatching is key.¬†(Kenna has written a great resource covering masterbatching and efficiency!)¬†If you don’t know what masterbatching means, it is a term for measuring out oils and other ingredients for multiple batches of soap at one time. If I have to make ten batches of soap, I measure out all my oils at one time instead of ten times. This is a huge step towards efficiency!

Water discounting affects the soap differently in big batches, so I had to cut back a little on that. I like to hold back a big amount of water so that I can add that liquid at the end of the cook. With big batch hot process soap, a large water discount could mean trouble. The soap will get hotter, could potentially volcano over and over, and takes forever to cool down. (If you do try Sharon’s method, I recommend not doing a water discount until you have a few batches under your belt.)

Maintain a production calendar. A production calendar will help you get organized. An order for hundreds of bars of soap in a variety of scents becomes less overwhelming when you have a plan. Decide in advance which soaps you are going to make on certain days and stick to your plan.

Use a slab mold (if you can.) Using a slab will allow you to make more soap at one time. Plus, all your soap will be more uniform in appearance. When you make multiple individual loaves, you waste time weighing each mold to ensure they’re accurate. You don’t have to do that with a slab! (You can make¬†your own wooden molds, too!)

My slab mold that holds sixty bars of big batch hot process soap!
My slab mold that holds sixty bars of big batch hot process soap!

Buy your ingredients in bulk. You will save a lot of money on your ingredients when you buy in bulk. When¬†wholesaling, that money saved¬†can make or break your business! Always order what you need in advance. Don’t wait until you are out of lye or a particular oil to order more!

Be aware of what you can carry, weight wise. My current limit is twenty-five pounds: this is what I know I can safely handle. One day, I may work up to larger batches, but not right now. A stainless steel pot full of twenty-five pounds of hot soap is a little intimidating. I bought a massive ladle to scoop my big batch hot process soap to make it easier (and safer!)

Lots of swirly hot process soap!
Lots of swirly hot process soap!

You can swirl big batches of hot process soap, but keep it simple. Be thoughtful about which soaps you send to potential accounts as samples. If you send a soap with a complex swirl or an intricate design, they will expect something similar Рno matter how many they order. Keep your designs simple and easy to recreate.

Big Batch Hot Process Soap vs. Big Batch Cold Process Soap

“Why do you make your soaps using hot process when cold process seems like less work?”

Well, there are a few benefits for me that keep me cooking my soap for production soapmaking.

First, the faster¬†turnaround time is a huge benefit. I can make a big batch of soap and deliver it with two weeks. For my big accounts that are busy, this is a huge advantage. In some cases, the fast turnaround¬†was the reason I won over the account. It allows me to make soap “on demand” – meaning I can wait until someone wants to buy a particular soap to make it.

The alternative would be to make a huge amount of soap, store it somewhere, and wait until someone buys (fingers crossed). This allows me to offer more options to my accounts, and saves me from having to store inventory that may not sell.

A slab of big batch hot process soap before cutting it up.
A slab of big batch hot process soap before cutting it up.
A slab of big batch hot process soap cut into six loaves.
A slab of big batch hot process soap cut into six loaves.

Another reason why I make big batch hot process soap instead of cold process soap is less limitations. I can use any scent (fragrance oil or essential oil) or any colorant, and I know what will happen. Since there is no ricing or accelerated trace or morphing of colors, my hot process soaps are reliable and consistent. If a client wants a soap in a fragrance I have not used before, I am not worried about how the fragrance will react during saponification.

Big batch hot process soapmaking is not for everyone, but, for me and my business, it has been a great fit!

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27 Responses

  1. I met Sharon last summer and fell in love with her process. I don’t know if I was mixing too much with the stick blender constantly on for the 10 minutes, but I blew out 2 stick blenders, so I tried the new ones, which looked like a better model, that I saw others using. They were very loud, heavy and the button was so hard to press and holding them in for so long seriously hurt my hand. I started getting terrible painful cramps in my wrist and was having trouble straightening out my hand, so I stopped and now I’m back to regular hot process, just mixing then putting the cover on. I have the larger crockpot, so I can do 2 loaves at a time. I’m just selling at festivals and online, no wholesale yet, but would like to. I know she sells her handbook with all the details, but can you tell me how much you’re mixing with the stick blender? When I saw her demonstration it looked like she was blending most of the time, just near the end going in short bursts.

    1. I use my stick blender for only a minute or two – until I get to thick trace. And then I cover it and let it continue to cook in its own. I stay very close until it vocanoes the first time, stir it down and then let it continue to saponify on its own. I have had the same cuisinart stick blender through hundreds of batches and thankfully have not burned it out yet!

      1. When I saw her demonstration she was using the stick blender most of the time. I noticed that if I wasn’t blending or stirring, the temperature would go down, but she said not to let the temp go below 170 before I hit the final stage. So you’re saying I could get a giant stainless steel pot, heat my oils up, and pour in my lye, leave it alone and it will saponify right in the pan without losing heat or solidifying?

  2. Hi Molly, What’s the maximum water discount one can take with Sharon’s method. I usually like to use different milks as liquid in cp, but understand it’s better to use water or tea with Sharon’s method and add milk after the cook. Would like to know what’s the maximum discount I can use before and what’s the maximum liquid that can be added after the cook. Also what’s the maximum super fat %(oils n butters ) that can be added after the cook. Thank you for your help.

    1. I am not sure what the max limits are, however, I soap at 35% liquid. I like to swirl my soaps, so if you want a single color you can go lower. I superfat at 8% but don’t know what would happen if you went higher.

  3. Thank you for your reply !!! One more for you, if adding oils like avocado ,almond etc is it better to add after the cook or with the rest of the oils?

  4. This was one of the best articles I have read on hot process soaping. I am at the point, like one of the soapers above, where I am using the larger crocks and still working in loaf molds, but production is about to jump up and I am not quite ready for it. Did you ever try a paint mixer attachment to a drill (like some people use when they large batch CP)? I am trying to imagine how large the pot is for the 25 pound batch you described, and how a stick blender will fit down into the pot without being too short. Am I missing something? Any tricks or tips on designing your own mold? I have never been much good with math, lol…am scared we will design and build a mold that doesn’t hold the right size bars that I need. Thanks for any help.

    1. Thanks so much Kirsten! I have a whole bunch of different pots at this point, which I very in usage depending on how big of a batch I am making. I like my batter to take up no more than 1/4 of the pot to allow for volcanoing. This is why the stick blender still reaches into the soap without issue. Some HP soapers have huge stick blenders but I am still using the same cuisinart blender I have had for a year and a half. My husband made my molds out of plywood and my only tip is to make sure that they don’t concave in or the soap won’t come out! good luck! Molly

  5. Hi, those look great, but I have a question: do you find that soaps cure irregularly with HP?? Mine do, and that’s one think I don’t like about it. I love how smooth CP is. I make HP with 30% water hoping it will prevent uneven shrinkage. But I can still see it. Do you have that?? Thank you. ūüôā

    1. I do notice that my bars harden more quickly when the humidity is very low, but i plan for that in my process. if you are referring to warping, I have had issues with that when i add too much water when mixing my colorants, but if i am careful about that, i don’t have warping.

  6. I tried this method of hot process, and it became a big disaster! Why? Because I’m very inexperienced, and it was my first ever attempt at hot processing. It did work, yes, it became soap, but I had to throw it away. I burned everything because of inexperience. Burned milk, oats and sugars had to go straight in the bin. Plus a jelly lye solution because of cornstarch in the lye solution.

    But now I have learned. Learned a lot! I know that if the soap separates badly, as mine did, it will go toghether again with stick blending. I have learned not to add things too early that can burn too. And I have learned that cornstarch can not go into hot lye! Also learned that I had to stick blend a lot more than I thought I would. And seen that it went really fast from scratch to finish. And most important of all, I have learned NOT to make a big batch if something is your first ever try and when unsecure of the process. It’s not funny to throw away a big batch.

    The volcanoes, yes, I was really prepared for that after seeing lots of Youtube videos. So that was no problem at all. I knew that I could not leave my soap for even one second.

    So I will try this fast hot process method again, for sure. Now I know a lot of what not to do, and that is a start. And I don’t have a crockpot, and don’t want to buy one either since I don’t need it, so this method is perfect. And it was the only hot process method I could try apart from microwave hot process, which is sort of the same. But since it worked like magic, apart from burning and jelly-lye, I definately not need any crockpot. The method itself is great!

    I didn’t make any swirls or anything. I had plans to do so, but since I knew early it would fail, I didn’t bother. I just wanted to go thru the whole process instead of quitting and see if the vaseline stage would appear, and if I could master this techniqe of hot process. And it did, and I could. And the mold was the next goal, just to get it cold and in a manageable stage to throw away.

    I also learned that I have to buy some heavy duty commercial grade supplies. The spatulas and such from the local grocery store was in such a bad quality that it totally was destroyed, even before I tried to stir! The cold process batter had destroyed it, or the dishwasher, or just by looking at it. So such crap does not work for anything, and especially not soap. That’s why I used the stick blender a lot, the only heavy duty item fit for the job. So I learned a lot from my very failed batch of soap, and hopefully I don’t have to throw away the next batch. I will make HP soap on a rope (which was the original plan all the time), so we will see if I manage to get it right and get the ropes where it should be and not float around everywhere else.

  7. Hi! I have a question in regards to master batching. I like to mix my oils and stash them away for when I need to make a quick batch. I combine my oils and store them in pouches so I am always ready. When doing hot process is there any issue or loss of integrity when heating my oils twice? Once when I combine them and a second time when I actually use them? Thank you.

  8. Hello Molly! A great article as usual. I have a few questions for you and I hope I’m not overwhelming… I was wondering what are the dimensions of the slab mold you used? What tool did you used to cut the soap into the six loaves? How many bars of soap do you get out of this specific slab mold and the oz per bar? Thank you!

    1. my husband makes my molds for me and they are 15 x 11. I use a log splitter to cut the slab into logs. the mold has a removable panel so it can make 40, 50 or 60 bars of soap. If i cut into 6 loaves that becomes 60 bars. hope this helps!

      1. Thanks so much! How many inches high is this mold? When you get 60 bars from one batch usually how many ounces is each bar approximately? ūüėä

  9. How many inches high is this slab mold? When you get 60 bars of soap from one batch usually how many ounces is each bar approximately? I was also wondering if your corner logs are rounded or not. Can’t see well… If they’re rounded do you shave them? Thanks in advance!!

  10. Hi Molly,

    Thanks for sharing. What does your lobster pot look like? Is it just a big steamer? Does it work like a double boiler? Is it electric?

    1. a lobster pot is a large, straight sided, stainless steel pot. Also used to make giant batches of soup, sauces, etc. in a commercial kitchen. it is not electric. it is not a double boiler. Just a run of the mill big pot (must be steel though – never aluminum!)

  11. Hello Molly,

    Much needed article i should say.

    I have been making SJHP since 1.5 years. My usual batch size would be 3 kg, of which oils will be 1.6 kg. I had no issues with making small batches. Instead of 10 mins i used to finish my soap in 15 mins. I always made my soaps in Stainless steel vessels.

    Due to wholesale orders, from past one month i started making bigger batches of SJHP i.e about 7 kgs. I use a large stainless steel vessel. My water portion is 25% of oils. Although i am able to successfully make soap, i am having many issues. My major issues are :

    1) Its taking about 40 mins from start (mixing oils and lye stage) to finish. Even i change the water % to 33 % of oils it taking the same time. There is no change in behavior of the soap.
    2) The soaps is volcanoing faster but is staying seprated for longer periods. Frequent force pulsing is being required. The separated soap is having poridge like consistency
    3) soap is not getting emulsified faster

    Did you face similar issues? how long dose it take for you from start to finish ? i am getting frustrated and looking for turning back to traditional hp.

    The below are the steps of how the soap is behaving:

    1) I blend the soap for 2 mins after pouring lye water (oils temp at 93 degree celcius and lye water at 77 degree). The soap stars separating and volcaoning at only 86 degree Celsius.
    2) After stirring down the volcano the soap dose not emulsify properly , nor dose it volcano again. It has a consistency of a poridge
    3) I have to pulse for a while and the soap volcanoes again. By this time the soap turn translucent and would be about 83 degree to 84 degrees. At this stage i can see the oils floating on the soap.
    4) I have to pulse for one more time then the soap emulsifies properly. At this stage the soap PH will be about 11 to 12
    5) I have to let the soap sit for 5 to 10 mins then the soap PH drops to below 10.

    Thank you

  12. Molly
    This is the best article I have ever read in this topic. You have made me travel through the small batch to big batch production.

    Thank you so much for explaining it clearly. I am going to try this in sometime.


  13. Hello! Thanks for this beautiful article! It helps me a lot! Actually I didn’t think it would be possible to make big batch HP soap. My big struggle is when it’s time for my soap to dry. It takes so many weeks then I’m afraid to pack them in case making it may affect their quality. I’m going to try all tips here and in your others articles. I’m sure it will work, so I’d be able to pack my soaps.

  14. I use only palm kernel oil to make my bar soap I recently started adding animal fat to it though its cold process I want to start hot process soap making I don’t know anything about hot process soap could u please send me d procedures in making hot process soap via my email santity23@gmail.com

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