How to Make Cold Process Soap

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How to make cold process soap
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As the long-term effects of antibacterial soaps become more widely known, people are turning to more natural alternatives. This movement has resurrected the art of soap making. If you are new to making soap you are in for a real treat! It can seem like a daunting undertaking at first but it is such a rewarding process.

No farmer’s market would be complete without the beautiful array of homemade soaps. It is wonderful to support these local vendors but if the price-tag is out of reach for you, don’t despair. You can still ditch the antibacterial soaps by making your own homemade cold process soap!

How Is Soap Made?

Soap is a chemical reaction that occurs as a result of mixing an animal or vegetable fat with a base (sodium hydroxide). This chemical reaction is called saponification.

Merriam-Webster defines saponification as “the hydrolysis of a fat by an alkali with the formation of a soap and glycerol.” OK, so what does that mean?

Each fat has a unique combination of triglycerides. Triglycerides are compounds made up of a single molecule of glycerol and 3 fatty acids. Each combination requires a different amount of alkali to complete the saponification process. The alkali in soap-making is sodium hydroxide, also called lye.

The lye is mixed with water to create a basic solution. This solution is then mixed into your fats. As they are combined and begin to react, the glycerol molecule is separated from the fatty acids. The fatty acids then react with the hydroxide ions in the lye solution. This is saponification.

The two resulting products of the saponification process are glycerin, which is wonderfully moisturizing for the skin, and soap. No lye remains as it has all reacted with the fats to create a completely new substance.

Worried About Lye?

As I covered in-depth in this post, it isn’t truly possible to make soap without lye in some part of the process. Lye is the necessary agent for saponification and any true soap, even one you buy, is made with it. You can purchase a pre-made soap base but it is much less budget friendly.

Cold Process Soap vs. Hot Process Soap

The method you choose is a matter of personal preference. This post is to teach you about cold process soap but you can take the same recipe and use the hot process method instead.

Both of these methods begin in the same way. You make a lye/water solution and mix it with the oils to begin saponification. To make a cold process soap you would incorporate any additives and pour it into the mold as soon as it reached trace (more about trace later).

For hot process soap you would let the soap batter “cook” in a slow cooker on the lowest heat to accelerate and complete saponification. Then you would stir in your additives and mold it.

Cold process soap takes 4-6 weeks to completely saponify and be ready to use. In theory, hot process is ready to use immediately. However, it is wise to let it sit a week or so to harden a bit. This will make it last considerably longer.

I have made soap both ways and I like each method for different reasons. Cold process soap is easier to pour into the molds so if you are trying to use a mold with a design or pattern I would recommend cold process.

I like hot process for my everyday soaps (especially because I don’t always get them made on time, *ahem*), so it is great if I am in a pinch and need soap, like, yesterday.

Both methods are great and in the end you get the same result, soap! If you would like to try hot process you can try my recipe for basic slow cooker soap.

Ingredients for Making Soap

The most basic ingredients you will need are water (distilled is best), lye (sodium hydroxide), and some type of animal or vegetable fat (such as olive oil or tallow). These three ingredients are essential and it is wise to use a lye calculator to accurately determine the ratios needed for proper saponification.

There are countless combinations of oils you can come up with for a soap recipe. Each fat or oil has it’s own impact on your finished product. Some are great cleansers while others are more gentle and moisturizing. Some make large bubbles as opposed to others that create a low lather.

You can use all of one type of oil or a mixture of several different ones. A pure olive oil soap, also called castile soap named for a region in Spain, makes a very gentle bar of soap. A pure tallow soap has high cleansing ability and makes a great laundry bar.

I personally like to use at least two different oils to give the soap a bit more character. With a blend of oils it is much easier to achieve the qualities you are desiring in a soap.

Some of the most popular soaping oils are:

  • coconut oil
  • olive oil
  • castor oil
  • cocoa butter
  • mango butter
  • sunflower oil
  • sweet almond oil
  • jojoba oil

If this will be your first time making soap, a good place to start would be to use olive oil, coconut oil, and castor oil. This combination will give you a mild soap with a good lather and these oils are easy to come by. We will use these oils in the instructions below.

Optional ingredients can be added to customize your soap recipe. Essential oils added after trace are a natural option for giving your soap a lovely scent. Clays add a silkiness to the soap that is especially good for shaving. Sea salt soap (do not use dead sea salt) is exfoliating and detoxifying.

Ground coffee, oatmeal, and botanicals like dried lavender flowers or herbs give a nice texture to the soap. For a natural colorant you can try adding mica powders, cocoa powder, turmeric, or spirulina.

As you learn more about soap making you can even experiment with alternate liquids such as goat milk, herbal tea, or even beer.

Working With Lye

Lye is used to make all soap. Even melt and pour soap bases were originally made with lye. There is a common misconception that soap is not natural or healthy if it is made with lye. This simply isn’t true. It is necessary to use lye to achieve the chemical reaction, but you can be assured that when done correctly, no lye remains.

In fact, most soap is “super-fatted.” This means that there is extra fat worked into the recipe so that there is no possibility that any lye will remain. This also makes the bar more moisturizing. A good rule is to superfat by 5%.

I would guess that working with lye is the greatest deterrent for people who are thinking about making soap. I can understand how this would be a stumbling block but if you know and follow proper safety measures, you shouldn’t have any problems working with it.

Lye safety measures

  • Wait until children are in bed. Making soap is not an activity to do with children. Watch out for pets as well. Children and pets can cause distractions or spills.
  • Wear long sleeves and protective gear including safety glasses and rubber gloves.
  • Make sure your workspace is free of clutter that could cause a spill. Also, remove anything that could be ruined if a spill were to happen.
  • When the lye and water are mixed it will create fumes. Do this step in a well-ventilated area or even outside. I prefer to do it outside so I have no concern about fumes and then if I were to spill (I haven’t yet) it would not be in my house.
  • Always add lye to the water. DO NOT add water to lye. It will create a caustic eruption! The adage in the soaping world is “snow floats on the lake.” It MUST be done in this order.

Hopefully these safety tips serve to make you feel more comfortable working with lye. The first time is a bit nerve-wracking but once you have done it you will see that it is not so frightening!

Cold Process Soap Making

Now that we’ve got those little details out of the way, let’s get into the nitty gritty of soap making, and more specifically, the cold process method!

Soap Making Supplies

I have a set of tools I keep just for soap-making. It is not absolutely necessary to keep them separate but it eliminates any possibility of not getting your tools clean enough for food preparation.

  • Non-reactive pot or slow-cooker for warming oils
  • Heavy plastic pitcher or quart mason jar for mixing lye/water
  • Second jar or disposable cup for measuring lye
  • Infrared thermometer or 2 candy thermometers
  • Mold (this one will fit this recipe)
  • Digital scale
  • Stick blender
  • Spoon
  • Spatula
  • Safety glasses and rubber gloves
  • Lye – I have purchased lye online and also at a local hardware store. (Try a smaller store as the large chain stores do not typically carry it.) You will have to ask an employee for it.
  • White vinegar for final cleanup

How to make cold process soap
3.79 from 19 votes

Basic Cold Process Soap Recipe

Ditch the antibacterial soap and make your own beautiful cold process soap at home.
Active Time1 hour
Resting and Curing Time29 days
Yield: 12 bars
Author: Katie Wells




  • Prepare your mold. Wood molds will need to be lined with freezer paper or wax paper. Silicone molds are ready to use as is. You can also use any box if you line it with freezer paper, wax paper, or a thick garbage bag.
  • Put on protective gear, place a glass jar on the scale, and tare the scale.
  • Pour distilled water into the jar until it reads 12.54 oz.
  • Set aside.
  • Put a second jar on the scale and tare the scale.
  • Carefully pour lye into the second jar until the scale reads 5.09 oz.
  • In a well-ventilated area or outside, slowly pour the lye into the water.
  • Stir the mixture until the lye is dissolved. It will become quite hot so be careful if you need to move it.
  • Let this mixture sit and cool to between 100-120°F.
  • While the lye is cooling, measure all other ingredients EXCEPT the essential oils and warm them together in a pot or slow-cooker.
  • Once they are melted, remove them from the heat and let cool to between 100-120 degrees. I use the infrared thermometer about every 5-10 minutes to test the temperature. This works really well, but a candy thermometer placed in each container also works. If one is cooling faster than the other you can put your oils back on the heat source or the lye/water mixture in a warm water bath to slow the cooling process a bit. Ideally, you want the lye/water and the oils to both be between 100-120 degrees and within 10 degrees of each other.
  • When the temps match, slowly pour the lye/water into the oils.
  • BEFORE you turn your stick blender on, make sure the blade is completely under the mixture or you will splash it everywhere. Use the stick blender to bring the batter to a light trace. It should be slightly thick and resemble cake batter.
  • If using, add the essential oils now.
  • Blend essential oils in by pulsing the immersion blender a few times. This should bring the mixture to a medium trace. You can tell when you have reached a medium trace by lifting your blender up out of the mixture (in the OFF position) and observing how the drips behave. They should leave a trail or “trace” on the surface. If you don’t use essential oils, just pulse your blender a few more times to bring it to medium trace.
  • Pour the soap batter into your prepared mold, using a spatula to get it all out. Remember that the soap is not fully “cooked” yet at this point and could still irritate your skin so you should still be wearing your gear.
  • Put the mold somewhere it can sit for 24 hours.
  • Place an upside down cardboard box over the soap and cover with a towel. If your house is warm the towel may not be necessary.
  • Let sit for 24 hours.
  • You can now remove your soap and cut it. This recipe in the silicone loaf mold makes about 12 bars weighing approximately 4.5 oz each, but you can cut them whatever size you like.
  • Stand the bars up in a dry area with an inch or so of space in between to allow for air circulation and let them sit for 4-6 weeks. This will allow the soap to complete the saponification process. The soap will also lose some of its water during this time making the bar harder. The harder the bar, the longer it will last.


Soap Making Clean-up: 
Rinse the jars and any supplies that had lye or soap batter in them well, with running water. I have washed the tools two different ways. You can pour some vinegar in a sink filled with hot soapy water and wash them in there, or you can wash your well rinsed dishes in the dishwasher.

A Note About “Trace”

Most soap recipes tell you to blend the lye/water and oils together until you reach trace. What this means is that you will need to blend until there is no separation left in the mixture. If the lye/water and oils are not completely mixed, your oil will separate in the mold and leave pockets of lye.

When your mixture has reached a light trace it will resemble cake batter. A medium trace is more like pudding but still pourable, and a thick trace holds its shape. When you have gone as far as a thick trace, your soap will likely have to be spooned into the mold.

Have you made your own soap? Share your favorite recipe!

Ghee is a clarified butter made from removing the milk proteins from butter. It is a traditional sacred food in many cultures and has incredible flavor.

Katie Wells Avatar

About Katie Wells

Katie Wells, CTNC, MCHC, Founder of Wellness Mama and Co-founder of Wellnesse, has a background in research, journalism, and nutrition. As a mom of six, she turned to research and took health into her own hands to find answers to her health problems. is the culmination of her thousands of hours of research and all posts are medically reviewed and verified by the Wellness Mama research team. Katie is also the author of the bestselling books The Wellness Mama Cookbook and The Wellness Mama 5-Step Lifestyle Detox.


75 responses to “How to Make Cold Process Soap”

  1. Rebekah Avatar

    I tried your recipe today, and didn’t get to trace…my oils are still liquid and just that, oils! In troubleshooting, I found that my lye was probably bad. Why didn’t I think that my lye that was all clumped together had absorbed moisture and was no good??? 🙁 I hate to throw everything away…do you think I could add more (good, fresh) lye tomorrow and try again? Or, do you think that it would then be “lye heavy”? I really want to get this soap making down!

    1. Jessie Avatar

      I’m SO sorry ?! I hate it when that happens!
      Because you don’t know that exact percentage of lye that was actually still active, if you were to add the amount of lye originally needed, you could potentially end up with a very lye-heavy soap, dangerous for you and anyone else who used it!
      My suggestion is to chuck it all. It hurts, I know, but better safe than sorry. But it’s not a usual suggestion for mishaps. If it was a case of separation, I’d say leave it alone and hope it becomes a solid. And if it was only a little lye-heavy, I’d say rebatch it. But there’s too many unknowns here so it’s not safe to “just fix it”.
      Sorry, I wish you the best with the next batch!!

  2. Leslie Avatar

    Thank you for your wonderful natural, homemade recipes! They are changing my life. I have already made your crockpot soap recipe last week, and today I made this cold process soap recipe. It is so fun for me. It is my newer hobby, and I get a fun break while my kids are at school. God Bless you and your family. 🙂

  3. Bianca Avatar

    So glad I found this website. I am very new to this and I have few a questions about the finished product. When used, how does it feel on the skin? Does it leave a residue? Can you see particles floating in the water after use? We have been using Dove Sensitive for years and I like it because I don’t feel anything left over on my skin or in the bath water.

  4. Tracy Avatar

    If you want to super-fat your soap, do you just increase any one of your fats or the combination of fats by 5-7% and continue?

    What fats are the best for dry and sensitive skin?

    Thank you for all you do and information. Love your site so much!

    1. Jessie Avatar

      When you start thinking about your recipe (or even if you’re using someone else’s), you’ll NEED to run it through a lye calculator (Google “lye calculator” and use any that come up). In the form you’ll be asked what oils or fats you’re thinking of using, and either how much of them or what proportion of each one. The other questions are about lye concentration (or similar), and superfat. There might be other questions but those are the main ones.
      Superfat is how much of the total amount of oils you want to remain free (not turned into soap). Unfortunately, you can’t really decide which oil will be left free. Even making your soap by hot method won’t guarantee this. Lye is a hungry monster that will turn all available fatty acids into soap. The only way to guarantee that oils WILL remain free is to add just the right amount of lye to do this, hence the superfat option in your lye calculator.
      Your question as to which oils or fats are best for dry skin is kinda complicated. Let me explain:
      Coconut oil is considered to be very good for dry skin BUT, in soap-making, if you add too much you’ll get a very DRYING bar of soap, even though it’ll be very sudsy and a relatively hard bar. So coconut on it’s own will be moisturizing but in soap it’s very cleansing.
      Olive oil is considered the mildest of oils but if you make a olive oil only soap, you’ll get a very hard bar that takes forever to cure (be good enough to use), and there won’t be any suds, just a very thin and slimy kind of lather.
      Your best recipe for YOUR skin, or your purposes, will be a mixture of oils that have what you want.
      A really good beginner’s recipe is the one published here: olive oil (use light, not extra virgin), coconut oil (the cheapest for now), and castor oil found in the stomach section of your local drugstore or supermarket drug section). My personal recipe? 75% olive oil, 20% coconut oil, 5% castor oil. And I add 1 teaspoon of regular salt to warm bottled water per pound of oil (all the oils and fats together), added and dissolved before I add the lye to the water.
      Sorry this is a long-winded reply but, meh, I like being thorough. I hope this helps someone.

  5. Keli Avatar

    This is the absolute BEST article I have read, detailing how to make cold-process soap! Thank you so much. I can’t wait to get started 🙂

  6. Marley Avatar

    In soap, you can use either. Since you are not eating soap, either is fine for your use.

    Food grade lye is greater than 95% pure, and the remaining percentage is guaranteed to be food safe. Non-food grade is considered to be about 97% pure lye, but it is not guaranteeing that the remaining percentage will consist of food grade material.

    However, even products that are 100% lye will never be 100% pure. Just be sure the lye is considered 100% lye, and does not contain some other caustic substance that may be included for the purposes of cleaning drains. It should clearly say on the label: 100% Lye (Sodium Hydroxide) NaOH

    I have a personal preference for the Food Grade Lye available at many soap supply sites (Amazon, Essential Depot, Bulk Apothecary, etc) because it is readily available and comes in easy to use 2# containers. Even if I am buying 50# of lye, I want it in 2# sealed containers. Lye attracts moisture, so I don’t like the 50# sacks of it sitting around my workshop. Chances are you won’t use it up quickly enough to buy that much lye at once when you’re only using a few ounces of it per batch.

    Another lye that is easily accessible from the plumbing department of most hardware stores (Lowes) is the 2# container of Roebic. Roebic is considered 100% lye, and I have found it to be perfect in making soap. It can be found in the plumbing department because it is used as a drain opener. I have never had any problem using Roebic Lye.

    One particular lye that I am not in favor of using (although many soapers use it) is called Rooto and is available at Ace/True Value Hardware Stores. It comes in a 1# can and is cheaper than Roebic. If this is all you can find, go ahead and use it. It is fine for making soap; however, when you make your lye solution be on the lookout for black specks that are in the lye. Some minerals in your water (if not using distilled water) can cause black specks to appear in your lye solution; however, I have found black (metal like) specks in the actual can of lye. It’s just a pain to have to pull them out prior to using the lye. The lye itself is fine.

    Hope this answers your question.

  7. Crystal Avatar

    Food grade vs. non food grade lye. What’s the difference? I would imagine the impurities in the non food grade lye would affect the quality and/or consistency of the soap. No? Thanks. LOVE your blog, but LOVE.

  8. christie Avatar

    Can you use stainless steel bowls or should you use plastic when mixing?
    Can you also use lard? I saw another video where she uses lard, but you only mention tallow.
    Thanks Katie. Super excited about trying this out.

    1. Wellness Mama Avatar

      You can use lard. I’d recommend a soap calculator to make sure that the fatty acid proportions stay correct if you sub lard for one of the ingredients though. Steel should be fine for mixing, just make sure to avoid aluminum or other metals.

      1. Marley Avatar

        Plastic Recycle No. 5 is also safe for both your lye mixture and for your mixing bowl. One way to avoid having to designate a separate cooking pot for solely soap making, is to use whatever pot you have for JUST melting your fats. Once the fats are melted, you can transfer them to a plastic (No. 5) bowl and continue to make your soap in that plastic bowl. The only thing that went into your cooking pot is fat, which will in no way prevent you from using it again for normal food preparation.

    2. Jessie Avatar

      @Marley is right, but I’ll add that HDPE, plastic #2, will also be heat resistant. Those are large yogurt containers, as a for instance.

  9. Sarah Gutierrez Avatar
    Sarah Gutierrez

    Thank you for posting this. Could you give a few recommendations for types of salts to use and what the benefits would be? Thank you and God bless you and your family.

  10. Moe Avatar

    Wow, thanks so much for this information! I have yet to come by anything you’ve written that hasn’t worked! And the beauty of it is that your recipes can be tweaked with and given a personal touch. I bet a lemon and Ylang ylang would smell just dreamy. Then again……maybe not? Haha.
    I read awhile ago you were expecting……and perhaps you’ve had the babe by now, but I just wanted to say congrats!! I have four of my own and life is busy as it is. So I admire you to bits for all this work you do!! And the help you have given me for natural living!
    God bless you and yours!!!!!!!

    1. William Ridgeway Avatar
      William Ridgeway

      Hi I have a question, Can hot process soap be reheated and then add other fragrance items to it? Bill

      1. Teresa A Oberg Avatar
        Teresa A Oberg

        Bill, You can!!! It is not as easy as you think though. I shred soap I want to repurpose – but only soap I have made. I use a cheese grater to make them into tiny bits and add them to a crockpot with a tiny bit of coconut milk, then heat on low until it starts “melting” – adding coconut milk to make it a little runnier so it can be remolded. You have to be careful here, you can at any point add more milk, but you can’t take it away if you made it too slushy. after it hits an almost translucent color, it is pourable and ready to add an additional fragrance and mold. Alternately, you can take those same shreds, add them to new soap batter (you can do the weighing to decide how much to make by subtracting the weight of the shreds from your standard batch – just run it through the saponification calculator.) This method has actually made some of my favorite soaps!

  11. Allison Avatar

    A mason jar might crack when adding sodium hydroxide to water. Better to use a strong plastic or stainless steel.

    1. Marley Avatar

      This is a good recommendation, Allison. Using a glass vessel repeatedly for your lye mixture (even a Pyrex one) can cause the glass to become “etched” and can eventually shatter at some point in its life. Some people think this is not a valid precaution, but having had it happen to me I can tell you that I would take this precaution seriously. I use a stainless steel container or a Plastic Recycle No. 5 container. If you insist on using a glass vessel, I suggest swapping it out for a new glass jar every few batches.

  12. Jon Avatar

    Silly question….How do you cut them? Is it easy?
    Can the stick blender and all other tools and bowls be used for food prep or do they have to remain dedicated to soap making?

    1. Jessie Avatar

      If this is just a hobby right now, best of all is a cheese cutter, the kind used in bygone times at cocktail parties. Next best is a very thin bladed knife or baker’s bench scraper. Last of all would be a regular chef’s knife that’s not very thick or a bread knife.
      As for segregating the equipment, I don’t and I’ve been making soap for friends and family for over 3 years. The plastic pitcher I use to dissolve the lye and the small plastic disposable cup to measure it I rinse right away, if I can. The rest of the batter- or oil-covered equipment I leave piled up for 2 days so the batter can saponify and able to wash itself and the oily stuff. The one thing I do that’s a bit more is to use a toothbrush to make shrub sure the blade stem of the stick blender doesn’t have soap stuck to it. Not that it’s bad just would add a strange taste to our refried beans!
      Have fun soaping! ?

  13. Susannah Avatar

    I love making soap. I like to add chia seeds for a little exfoliation. I enjoy experimenting, but I usually make fairly basic and not very attractive soaps for family use only. I usually use a blend of coconut & olive oil, but sunflower and grapeseed work well too. I usually just stick to hot process. I made cold process thinking it would turn out a lot better and there we no discernable difference. I like to superfat to about 6 or 7 % so it isn’t drying, but doesn’t melt awaytoo quickly.

  14. Christy Avatar

    Excellent recipe, can’t wait to try it, no matter, will keep this precious information it will always be useful. Thank you!

  15. fiona Avatar

    I make tomato soap with great results. I use canned or fresh tomato’s and puree them. Then freeze them which slows down the cooling process after I add the lye. Just add the lye to the frozen tomatoes and they will melt to almost the right temperature. Don’t add any water. I add basil or other herb eo.

    Sprinkle a line of dried herbs down the soap so that when its cut , each piece has a bit of herbs in it. It looks great.

    1. Anna Avatar

      5 stars
      This recipe looks great! I was wondering if you could sub out the coconut oil for a different one? My husband maybe allergic and I’ve been looking for one without it

  16. Harmony Avatar

    Oh my Goodness!! It’s amazing to me that you post an article on Exactly what I’m trying to learn or research! It’s like you’re reading my mind & and do so Frequently! Just yesterday I purchased lye and last evening was reading your post about hot process soap – ( because we need some like yesterday”.. ahem!lol ) and was scouring the Internet for recipes. My thought was to make a batch of hot process that we can use in a week or so and then make a second batch cold process…
    I know you’ll be welcoming a new lil Love sometime this month and am keeping you and your family in my prayers that this labour will be shorter & easier than the others! 😉

      1. Veronica Avatar

        Hi wellnessmama, I purchased a soap stamp for my soaps. When would I use it with the cold process and the hot process?
        Thanks. Keep up the good work!
        Veronica. 🙂

        1. Jessie Avatar

          In soap-making, ALL measurements are by weight for most accuracy. So, fluid or dry, every ingredient is measured by weight, be that ounces or grams.
          Personal preference, I use grams because they’re more accurate than ounces.

        2. Jessie Avatar

          Sorry! I’m not sure why my comment for another poster got posted here!
          But, this is for @Veronica, about stamping her soaps.
          The best time to stamp them would be before they’re so hard they won’t take the stamp. And that will vary between soap recipes. Some will harden very quickly (thinking of salt bars), and others might be too soft for days (high olive oil bars). You’ll have to be your own best judge.
          Happy soaping!

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