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How to Better Understand Water Discounts When You Make Soap

One of the most common issues I run into with soapmakers is not understanding how the lye solution in soapmaking works. For instance, a soapmaker might take one of our recipes and incorrectly use the “water as a percentage of oils” option instead of the “lye concentration” option and think there is something wrong with the formula. Or misunderstand how to partially replace the water in a recipe, like the Lemon Zest & Blueberry Yogurt Recipe.

Understanding Water Discounts and Lye Solution in Soapmaking

Even bigger issues crop up when a soapmaker tries to scale up and doesn’t understand the lye solution when trying to masterbatch or when they reach out for recipe help because the recipe is soft, traces too quickly, or takes a long time to cure!

Many soap calculators compound the issues by presenting the default options of calculating the water as a percentage of the oils, so newer soapmakers are missing out on this vital information!

Understanding Your Lye Solution in Soapmaking!
Understanding Your Lye Solution in Soapmaking!

Let’s talk about the elephant in the room first: what’s wrong with calculating your water amount based on the oils?

Simply put, you end up with a large variety of solution strengths! Different oils need varying amount of lye of to saponify, but the amount of water won’t change based on the lye. Since the amount of water present helps determine both your speed of trace and your cure time, this can create inconsistent results from batch to batch.

For instance, if calculating your water amount based on a percentage of the oils, these two formulas are wildly different:

100% Olive Oil Soap

  • 16 ounces of Olive Oil
  • 2.06 ounces of Lye
  • 38% of oils: 6.08 ounces of water
  • results in a 25.3% lye solution

100% Coconut Oil Soap

  • 16 ounces of Coconut Oil
  • 2.79 ounces of Lye
  • 38% of oils: 6.08 ounces of water
  • results in a 31.42% lye solution

The olive oil soap will trace slower and cure slower than the coconut oil soap, due to the varying lye solution strength from batch to batch, even if you made the soaps on the same day! However, the coconut oil soap will saponify even faster and enter gel phase at a much higher temperature (though the gel phase will be shorter duration).

The bigger problem with this is that olive oil saponifies slower than coconut oil anyways! It would be better to have a stronger lye solution and less water for the olive oil soap (so that it doesn’t take a year to cure and an hour to trace). Since coconut oil saponifies more quickly on its own, it would be more beneficial to have a weaker lye solution and more water so the lack of water isn’t compounding the issue.

If this is news to you, you might want to read up on controlling trace and the various factors that affect trace!

My biggest concern with calculating your water as a percentage of oils is that you might accidentally discount your water too much! If you aren’t keeping your lye in mind by calculating your water based on your lye, you could do something like this:

100% Olive Oil Soap

  • 16 ounces of Olive Oil
  • 2.06 ounces of Lye
  • 15% of oils: 2.40 ounces of water
  • results in a 46.19% lye solution

100% Coconut Oil Soap

  • 16 ounces of Coconut Oil
  • 2.79 ounces of Lye
  • 15% of oils: 2.40 ounces of water
  • results in a 53.72% lye solution

The coconut oil soap’s lye solution is too concentrated! Lye cannot dissolve into a solution with less liquid than its own weight. If you were to make this soap, it would be lye heavy and unevenly saponified, with free particles of lye in the bar.

In order to master water discounts and water replacements or alternative liquids, you must be able to understand your water in relation to the lye instead. The easiest way to do this is to look at your lye solution as a whole ingredient and calculate your water as a ratio of the lye.

The Most Common Lye Solution Strengths in Soapmaking

Most early soapmaking books and recipes use a “full water” amount, which is a misnomer as there is not a maximum amount of water you can add to a soaping formula. (Yes, you could use more!)

When most recipes refer to full water, they are usually calculating a lye solution strength between 25% and 28%, which means that 25% to 28% of the solution is lye and the remainder (72% to 75%) is water.

A 25% lye solution is made of 25% lye and 75% water.
A 25% lye solution is made of 25% lye and 75% water.

As we know, the higher the amount of water, the slower the trace (but also the longer the temperature phase during saponification). Using “full water” will give you the maximum amount of time at a workable consistency, but will also ensure a fully gelled soap in most cases (which may not be ideal!) It will also take the longest for a soap with a 25% lye solution to cure because there is a lot of water to evaporate.

The next most common lye solution strength is a 33% lye solution, which is ideal for a slightly faster curing time (less water to evaporate), reduced length of heat phases during saponification, and slightly harder bar straight out of the mold.

A 33% lye solution is made of 33% lye and 67% water.
A 33% lye solution is made of 33% lye and 67% water.

Most recipes and tutorials here on Modern Soapmaking use a 33% lye solution, as it’s typically a manageable water discount during the soapmaking process, but also hardens up a little quicker to get the soap out of the mold!

A strong water discount is typically referred to as a 40% lye solution. Reducing the water amount in your lye solution will help the soap get out of the mold quicker and cure faster. Compared to a soap made with a 25% lye solution, soap batches made with a 40% lye solution can cure in about half the time.

A 40% lye solution is made of 40% lye and 60% water.
A 40% lye solution is made of 40% lye and 60% water.

Keep in mind that a soap made with a stronger lye solution like a 40% solution will trace more quickly!

The least amount of water you can use to fully dissolve lye (at optimal temperatures and conditions) is a 50% solution. Remember, this means that 50% of the solution is lye and the other 50% is water. This is considered the strongest lye solution strength and the highest water discount possible.

A 50% lye solution is made of 50% lye and 50% water.
A 50% lye solution is made of 50% lye and 50% water.

It’s important to remember that your lye solution can be a maximum strength of 50% lye and 50% water in ideal conditions. However, if your 50% lye solution is used or stored in an environment that is too cold (less than 25° C or 77° F), the lye can precipitate out of the solution.

Using a lye solution where the lye is no longer dispersed in the liquid or water can cause uneven saponification and lye pockets. As such, I tend recommend using a weaker solution strength (40% lye solution) as the maximum water discount in most cases.

However, a 50% lye solution does become quite handy when you want to use alternative liquids. For instance, you can create a 50% lye solution with water and lye, and then add an additional liquid (such as goat’s milk) to the lye solution or oils. This will increase the water amount (slowing down trace), add additional properties, and reduce any issues with creating a lye solution with alternative liquids (freezing milk or scorching).

How to Calculate Your Water Amount for Your Lye Solution

When you calculate your formula, you usually choose your oils first, which then dictates your lye amount depending on each oils’ weight and saponification value. Then, you can determine your water amount by choosing a solution strength. A quick and easy way to do this is to multiply your lye amount by a corresponding multiplier.

Let’s say you would like to create a 50% lye solution and your oils dictate that you need 3.5 ounces of lye. You would multiply 3.5 ounces x 1 = 3.5 ounces of water. If you would like to create a 33% solution instead, you would multiply 3.5 ounces x 2 = 7 ounces of water.

If you aren’t sure what the multiplier is and don’t have the chart below handy, you can find out by doing a little math! Let’s say that you want a 25% lye solution, so you would:

(100% – Desired Solution Strength) / Desired Solution Strength = Multiplier

(100% – 25%) / 25% = 75 / 25 = 3

If you know you need 2 ounces of lye (because your lye is determined by your oils), and want to use a 25% lye solution, you would simply multiply your lye amount by 3 to find your water amount.

2 ounces of lye x 3 = 6 ounces of water

The table below covers the full range of multipliers from a 25% solution to a 50% solution, and highlights the most commonly used concentrations:

Lye Amount Water Multiplier Lye Solution Notes
Weight of Lye x 1  = Water Amount 50% lye solution maximum water discount
Weight of Lye x 1.1  = Water Amount 47.6% lye solution
Weight of Lye x 1.2  = Water Amount 45.5% lye solution
Weight of Lye x 1.3  = Water Amount 43.5% lye solution
Weight of Lye x 1.4  = Water Amount 41.7% lye solution
Weight of Lye x 1.5  = Water Amount 40% lye solution strong water discount
Weight of Lye x 1.6  = Water Amount 38.5% lye solution
Weight of Lye x 1.7  = Water Amount 37% lye solution
Weight of Lye x 1.8  = Water Amount 35.7% lye solution
Weight of Lye x 1.9  = Water Amount 34.5% lye solution
Weight of Lye x 2  = Water Amount 33.3% lye solution moderate water discount
Weight of Lye x 2.1  = Water Amount 32.3% lye solution
Weight of Lye x 2.2  = Water Amount 31.3% lye solution
Weight of Lye x 2.3  = Water Amount 30.3% lye solution
Weight of Lye x 2.4  = Water Amount 29.4% lye solution
Weight of Lye x 2.5  = Water Amount 28.6% lye solution mild water discount
Weight of Lye x 2.6  = Water Amount 27.8% lye solution
Weight of Lye x 2.7  = Water Amount 27% lye solution
Weight of Lye x 2.8  = Water Amount 26.3% lye solution
Weight of Lye x 2.9  = Water Amount 25.6% lye solution
Weight of Lye x 3  = Water Amount 25% lye solution no water discount

Okay, what about if I want to just figure out my water amount without all this multiplier nonsense? Can do! Take your amount of lye and your desired solution strength and plug it into this calculation:

Amount of Lye / Desired Solution Strength x (100% – Desired Solution Strength) = Water Amount

Let’s say that you need 3.51 ounces of lye and want to use a 40% lye solution:

3.51 ounces of Lye / 40% Lye Solution x (100% – 40% Lye Solution) = Water Amount

3.51 / 40 x 60 = 5.265 ounces of Water

It doesn’t matter which way you decide to conquer the beast, as long as you are calculating your water amount based on your lye!

Why It’s Important to Understand Your Lye Solution in Soapmaking

Besides being able to control trace and curing time, understanding your lye solution in soapmaking will open the doors to being able to replace some or all of your water in a formula without concerns. You’ll be able to use multiple liquids or do a partial water replacement, without having to worry about scorching lye solutions or using too little or too much water.

For instance, in the Avocado & Argan Oil Soap Recipe, I used a 33% lye solution for the total formula. However, I substituted part of the water for pureed avocado.

Here’s the formula and the lye amount dictated by my lye calculator:

  • 8 ounces Avocado Oil
  • 8 ounces Babassu Oil
  • 7 ounces Olive Oil
  • 6 ounces Coconut Oil
  • 6 ounces Argan Oil
  • 3 ounces Castor Oil
  • 5.3 ounces Sodium Hydroxide

To find how much liquid I need for a 33% lye solution, I multiplied the amount of the lye by 2. I knew that the lye needed at least its own weight to dissolve in water (5.3 ounces). As such, I was free to use up to 5.3 ounces in avocado puree. My avocado was small, weighing in at 4 ounces, so I used a bit more water instead!

When you understand your lye solution in soapmaking, you’ll also be able to scale up your production easier with masterbatching. For instance, you could make a large amount of 33% lye solution to use in all of your recipes. (Just be sure to store your lye solution in safe, appropriate containers!) If you calculated your water as a percentage of oils, you wouldn’t be able to use one lye solution in different formulas!

To dive into really understanding your lye solution strengths, give Auntie Clara’s ghost swirl a try! It will show you exactly how varying lye solution strengths affect your soap during the production process, saponification, and cure.

When it comes to my own soapmaking, I prefer 33% lye solutions in smaller batches (five pounds or less) and 40% lye solutions in larger batches (more than five pounds). Do you have a favorite lye solution strength in your soapmaking? If so, leave a comment below and tell me why! I think it’ll be interesting to see what other soapmakers use as their go-to!

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139 Responses

    1. Thank you for sharing this article with me. I do have a question…you stated “your oils dictate that you need 3.5 ounces of lye” . How do oils dictate the amount of lye…is there a chart ones goes to to figure each oil being used and then you add them up? Please explain… I’d love to understand this math.

      1. Also in the article: “When you calculate your formula, you usually choose your oils first, which then dictates your lye amount depending on each oils’ weight and saponification value.”

        The saponification value (SAP value) of an oil is the number of milligrams of potassium hydroxide required for the complete saponification of one gram of that oil. While you can do the math by hand, there are many reliable calculators available, such as SoapCalc.net, Kathy.

        1. Im new to soap making and enjoying it. Really fascinating. I am a pharmacist by day and aspiring soap maker by night!! This is a very helpful article

        1. If you input 33% as the lye concentration for your recipe in a lye/soap calc, it should give you the amount of water and lye to make a 33% lye solution as discussed in the article.

  1. I prefer to work in ratios for some reason. Ever since I first started soaping I ignored the other options and worked with the ratios.

    I love a ratio of 2.2:1 for my main recipe which has a fairly decent amount of hard oils, it gives a good time to work with my batter, but a newbie would find it difficult.

    Soft oil heavy bars like my facial soaps are always a 1.8:1 ratio. If they’re all one colour I’ll drop it to 1.2:1.

    The pure olive and coconut oil soaps are 1.1:1. Olive because I want it hard fast and coconut at 0% superfat is only used as laundry soap. I want my coconut hard within 3 hrs, so I can unmould and grate it while it isn’t a brick you could build a house with.

    1. Ratios work! As long as it’s water/lye and nothing to do with the oils! 😉

      Sounds like you’ve really worked out what water discounts work for you & when, high five!

      1. hi, thanks for this article, am not so good at math but can cope once i start writing on paper.was trying to figure out how you got the lye amount (3.5oz x 2)for a 33% lye concentration and took my pen to paper and discovered its just a ratio 1: 2 lye to water and that felt easier.am definitely getting a hang of it now.

  2. Kenna ~ Thank you for your fantastic lesson on Lye solutions! Super well written ~ I understand the equations now, which is awesome since I don’t enjoy math. Thank you again 🙂 My favorite ratio I now recognize to be 33 %. Shorter cure, harder soap to unmold as you described, and still allows gel if I insulate &/or soap warmer… 120+ epending on ambient temps.
    Yay! Have a nice day!

    1. Yay! Happy to hear that! I know that not everyone is in love with math, so I try to break it down in different ways for folks. We all learn differently!

      33% lye solutions tend to be super popular for that reason – little bit shorter cure & faster setup time, but still pretty easy to handle. 🙂

  3. This helps so much! My vegan soaps were coming out so, so, soft because I was using WAY too much water in an effort to have more time for intricate designs (can we say “soap challenge” , lol?). However, this makes so much more sense than doing it as a percent of oils! Thank you! Here’s hoping my next all vegan batch won’t need three days in the mold and to be cut with fishing line to keep from smearing colors. (It was so. So. Soft.)

  4. Awesome post Kenna! My default is 35%, and then I tweak the lye concentration depending on the additives and EOs and how they affect the speed to trace based on previous experience with the particular recipe.

  5. This is so useful, it’s all so much clearer now! I had wondered what the purpose was of using different concentrations, thank you for explaining it so clearly.

  6. Thanks for this! I find this so confusing and the pictures really helped! That makes way more sense than however I had it not worked out in my head. If that makes sense. 🙂

  7. Thanks Kenna! Interesting, I would have never thought to use the water as a percentag of the oil….of course yiu’d want to manipulate the strength of your lye solution…i trued Auntie Clara’s ghost swirl…you are so right it really teaches you how different lye solutions make a big difference. It’s a fun thing to play with. Againg thanks! I love all of your posts!!!

    1. Yes! Clara is quite the soapy genius, if I may say so. 🙂 The ghost swirl is such a fantastic teaching tool while also creating some seriously stunning soap that would otherwise be considered “plain”.

      Happy to help! Thank you for reading along!

  8. Thanks for the informative article! I must say, you are one of the few, if not the only one that puts out informative articles like this. Most of them are general in nature and do not go into such depth. So glad I subscribed.

    I do have a question on making coconut soap….I love it, love the creaminess and the feel on my skin so I want to get it right. I made a small batch several months ago but was disappointed with the result and don’t know where I went wrong. I even posted on another forum but got no insight.

    Recipe as follows: 100% Coconut Oil, 33.3% Lye concentration. I placed my mold in the freezer for 3.5 hours thinking that this would prevent gel phase because I wanted a pure white soap. I unmolded about 19 hours later. The soap was pure white on the outside and somewhat soft and a bit crumbly. Once I sliced the bar, the middle had a large hard oval, just like a bar of soap that had gone through partial gel phase. I ph of the soap was around 9 and seemed fine to use.

    I want to make this soap again so any insight that you can offer would be much appreciated!

    1. That soap did have a partial gel. If you want to easily avoid the gel phase at all, you can use a higher lye concentration (38-40%) and you also don’t have to put the soap in the freezer.

      That is because the temperature that the gel phase is passing in a soap paste is based on its water amount.

      1. Nikos,
        I made another batch of coconut oil soap, 40% lye concentration. I mixed my le and oil together at around 100 degrees and poured it into the mold. I didn’t insulate or cover the mold, just left it in my laundry. It did go through gel phase, but all the way through. I unmolded it about 4.5 hours after pouring and cut it. If I waited any longer it would have been too hard to cut.
        I’m happy with how it came out. Though my question is, how do I avoid gel phase, or is that impossible?

  9. Thanks so much for this, Kenna! For years I’ve been ignoring the water box in soapcalc and I just use anywhere between 1.1 and 2.8x the lye weight. My go-to for anything swirly is 2.5, which thanks to your article I now know is a 28% lye solution. For layers and anything less intricate, I use 2x lye weight, so 33% and for olive oil it’s a good old 1.1x the lye . Thanks again! I had never learned what my proportions were in % terms and now I’ll understand this formerly foreign concept when other soapmakers talk lye solution % 😀

    1. I don’t know what the problem is but the highest concentration I’ve attempted is a 44% solution. Failed to stay solution. I did use clean vessels and utensils as well as distilled wated. I have used a glass vessel, plastic vessel, and a silicone vessel; all similar results. I stirred the lye water continuously for 2 to 3 minutes and it cleared but not for long. When i went to add the lye water to my melted fats, there was a very thin crystalline sheet of lye on top of the water. I diluted to a 30% solution and had no problems. My lye is 97% pure so i wouldn’t think that is the problem. The first time, i thought it was just because it was too cold(40°F) but i later made it on a warm day(70°F).

      1. As noted in the article, we tend recommend using a 40% lye solution as the maximum water discount in most cases.

        That said, it is possible for flakes or a thin layer of sodium carbonate to form on top of your lye solution when it reacts with the air. And, the stronger the solution, the more noticeable the reaction. That’s not a problem.

        If you have solids on the *bottom* of your container, that’s a big problem as it is likely lye that has not been held in the solution.

  10. That’s another good article that can help people on understanding the principal theory in soap making.

    As I also teach in soapmaking classes, I have seen that math is a very strange language in most of the women that are attending the seminars.
    So for me it works better to speak with ratio instead of percentage when it comes to Lye Concentration. The % symbol is unknown to most students and ratio seems to be more friendly as it reminds them of cooking.

    Furthermore many might not understand the very nice pictures that you share with the various lye concentrations and I have also heard a student asking me if with 40% lye concentration a recipe has more NaOH than with a 25%. Well as we can observe the pictures above without any math background, someone might understand that there is really more NaOH (pink area) in the vessel for a specific recipe. So ratio seems to be a more earthly explanation.

    I also call lye the NaOH in water solution.

    My most used lye concentration is 33% but I have started to like the 38-40% lately.

    Keep up the very good articles that you share and I wish you a lovely new year!

  11. Great article. Because of you I started using 33% in many of my recipes. However, your explanation of the various strengths of lye and water and their impact on the quality of a bar based on oils, etc. was a real learning curve for me. It answered a lot of questions I was having based on the type of bar and design techniques. I am going to try out Auntie Clara’s ghost swirl when I get a chance. Thanks as always for taking the time to educate and inform.

  12. I’ve never heard of this and am having a hard time comprehending it. We just use the lye calculator on Brambleberry for our recipes and seldom have problems.

  13. “I knew that the lye needed at least it’s own…”

    Just an editing note: “it’s” is a contraction meaning “it is.” What you mean to say is “its.”

    1. After reading such a great post, a misplaced ‘ is all you got out of the article? This blog is for soap making. But, there is always that one person who just has to post comments like this one.

    2. The contraction “it’s” is commonly misused. I remember looking that up a couple of times for myself when I used it incorrectly. I know what the commenters mean, but I always refrain from correcting them. I am by no means a grammar wiz and I actually appreciate when someone takes the time to politely educate or correct me. We learn through our mistakes, but I’ve found that many people don’t see it the way I do and become angry. I never know if the person doing the correcting is trying to be helpful or just rude and sarcastic. I most likely have a mistake or two here as well, but this is not the Writers Writing Right Club forum, so most people don’t care. 🙂

  14. Great post! I first learned about manipulating water in soapmaking when I wanted to learn how to masterbatch the lye and replace some of the water with milk. I turned to Kevin Dunn’s book on scientific soapmaking which was a great read, but this post does a great job of presenting the topic quickly and in terms that are easy to understand. Thanks for taking the time to write it up!

  15. Again, ANOTHER article that hits it out of the park, presenting concepts in an understandable format to the reluctant chemists among us (such as myself).

    I’ve always understood just enough about lye percentages/water discounting to get by, but THIS article really pulls the pieces together.

    Thanks, Kenna! You da BOMB.

  16. I love your article! I would discount my lye by 5-8% and use 15 oz as my base for water in a three lb batch of soap. So this concept is new to me. But i am not clear on how to figure out how much of a lye discount i am using with your calculation. I feel that your way gives me more control on the trace factor. But in order for me to do the change over from my way to yours i need to know that discount factor. Can you help? Thanks for your web site. I have learned a lot and i have been doing soaps for over 5 years. Who said you cant teach and old dog new tricks!!

  17. I feel giddy at the thought of masterbatching!
    How to calculate how much lye is in each ml of a certain concentration should not be a problem…really….but right now it is!

    Many thanks for a great article. The lye temperature thing may explain some soft pasty batches I made in a cold cold shed.

    Always pause for thought with your articles. Thank you.

  18. Hi ! In the avocado purée example, does that mean you add purée after trace? Is that what replacing means? Or do you add it at the same time? Also, how do you know when your soap is done curing especially if you are doing plain Jane soaps? Thanks! Love your blog!!

    1. I was curious about this too so I clicked on the recipe and it says she likes to add the puree to her soaping oils, then add the lye solution. HTH!

  19. I primarily use a 33% lye solution, but if I have an FO that accelerates rapidly I will increase my water. I just made a Gardenia soap which is known for ricing & seizing. So, I used every trick I know. I used a 27% lye solution, 30% canola oil, and soaped at 90 degrees. This gave me time to use 2 colors & it never riced on me. Thanks for providing the lye solution chart. The correct lye solution can mean the difference between a great soap & a soap FAIL!

  20. I’ve been using a steep water discount in all of my formulas and I haven’t had glycerin rivers since. But because of the water discount, I can’t achieve intricate swirls and designs. But if I don’t discount water at a 1.5:1 (water:lye) or lower ratio, I always get rivers. I have watched so many videos on swirling and intricate techniques, how do they have so much time to work with their batter, but not get rivers in their finished bar?

  21. Best tutorial ever! I have been soaping awhile using 1:1 pre made lye solution, then adding extra water to 33%. I have a Lilac fragrance that wants to trace too quickly.
    I needed a quick refresher on water discounting to increase water in this recipe. I had forgotten which direction to go , lower percent or higher!!
    It has been awhile since I have looked at water discounting, I got it now thanks so much, love your blog!

  22. Awesome explanation! I was wondering about the different options the soap calculators give. Now I get it and can make informed decisions for myself.
    I’m working on a shaving cream soap and this stuff is important because I want to use Aloe Vera gel without eating into the lyes’ water supply!
    Thank you very much for this clear and concise explanation.

  23. Can you help clarify if you added the lye to 5.3 oz of water and then later added 5.3 oz of avocado puree? Or did you add the lye to the 5.3 oz of Avocado Puree directly? Thanks – this was a very helpful post!

  24. I also prefer the ratios. It also depends on what type of soap I am making. CP soap gets a 1.8:1 (water/lye) ratio because I add 1oz of cream ppo after emulsification. HP soap gets 1.4:1 (water/lye) ratio because I add a few additives (cream, honey & water, yogurt and then superfat with additional oils) after the cook.

  25. I’m trying to wrap my brain around masterbatching lye water, which I would like to do at a 50/50 ratio; however, I usually like to do a 15-20% water discount for my soaps. How would I calculate the amount of liquid/water to add back into my lye water masterbatch solution that includes a 15-20% discount for a recipe?

    Would I take the total number of water called for to add back and multiply it by .15 or .20 to determine the discount? For example, if I calculate that I needed to add 6.15 oz into my masterbatched lye water amount for a full water recipe, would I then multiply 6.15 X .20 to give me a 20% discount amount, which would be 4.92 oz. to add to the masterbatched lye water amount?

  26. Thank you for this useful information. I have been soaping since 1992 but in the last 5 years I’ve come to understand all the ins and outs of soap making.

  27. I do but don’t understand water discounts. I really, really sucked at math and still do to this day. Been over yrs since I graduated. So that should tell you how much I hated math :)….So if one wants to add cream and water to a recipe. How does one calculate that. I am getting so frustrated at this “soap making” gig that I don’t even want to attempt to make soap anymore. Please help!!!! Thank you 🙂

    1. have you ever tried whipped soap by pre mixing the lye and water solution and letting it cool then you whip your oils together and add in the lye solution! you have 30 minutes plus of play time since there is no heat issue to deal with and it makes Beautiful soap.

  28. On a recipe that called for 6.08 ounces of water and 2.25 ounces of lye, I confused it with 6.80 ounces of water instead. How will that affect my recipe?
    My recipe:
    4 oz Olive Oil
    4.8 oz Tallow (Beef)
    2.4 oz Shea butter
    4 oz Coconut Oil
    0.8 oz Castor Oil

    BTW: I also add 1 tsp. of Sodium Lactate to the oils.

    Please help! I am new to soap making.

    1. Hey, Cheryl,
      So, instead of adding 6.08 ounces of water to your batch, you added 6.8 ounces? Well, you lucked out, because water amount is probably the most flexible part of a soap recipe. Your soap may stay softer longer, and it may have some shrinkage, but, as long as everything else was on point, you should still have soap!

      That said, be sure to check and recheck your ingredients and amounts for every recipe. (And yes, we recommend a literal check sheet so you can tick of ingredients as you add them!) Had your mistake been with lye weight rather than water, that would be a bigger issue!

      Hope that helps, Cheryl!

  29. Hello there!
    I have a question: what happens if I calculate the water and the lye according to the oils (with 25% lye to water) and then add some more water (without adding more lye or oils) ? So in this case actualy I don’t have lye discount, but I have excess water.

    1. Irene,
      What’s your goal in doing this?

      Extra water is going to cause your bar to be softer longer/take longer to cure. In extreme cases, as it cure, it will become misshapen: the surface will sink in as the water evaporates.

  30. Hi love this article!!! Finaly some one explain perfect how it works… I have a question if I use a water discount formula can or cant use sodium lactate in thr recipe??
    Thank you!!

  31. So, if i use the 33% lye solution, do i still need to do a lye discount or does this calculation take the lye discount into account?

    1. Your lye discount (aka superfat) is not impacted by your lye solution strength.

      Think about creating a formula. You generally choose your oils first and then decide on your superfat amount, determining the amount of lye you need for the recipe.

      The amount of water in a recipe changes with solution strength, but the amount of lye does not.

      Hope that helps, Irene!

  32. This formula, with 25% concentration as an example:

    (100% – 25%) / 25% = 75 / 25 = 3

    Is more simply expressed as 100/25 – 1, Since percentages are really just parts per 100, you’re turning it into a ratio i.e. how many parts of water to lye. In the 25% example, there are 4 total parts (100/25), of which one is the lye, which is why you subtract 1. A 25% solution is made with a ratio of 3:1, lye:water. Essentially, the purpose of the formula is to turn a percentage into a ratio, so it’s confusing and needlessly complex to subtract a percentage first. The percentage you’re subtracting is just the ‘part’ lye before you’ve properly converted to a ratio.

    So, to generalize it: 100 / Concentration Percent – 1 = Water ratio normalized to 1.
    Or, for a more complete general formula: (100 / Concentration Percent – 1) * Lye Measurement = Water Measurement

  33. I’m finding it difficult to get long enough to work my soap as it is tracing so quickly. My recipe seems right but it traces in 30seconds even at room temperature as well as 100 degrees F. It sets perfectly and is easy to unmould which I love but hate that I don’t have time to even add a fragrance or colour as it’s so thick.

    7oz olive oil
    7oz Coconut oil
    7oz Palm oil
    1oz Castor oil
    3.1 Caustic soda
    8 oz water
    I usually exchange the water for 3.1oz water and 4.9 goats milk.
    Could you help me as I would love to get this recipe right.

  34. Thanks for this article!
    I’m curious if my normal soap batch makes 5 lbs of soap, and I want to water discount my recipe, will it then make less soap?

    1. Heather, since the bulk of your water evaporates during cure, the difference in your end yield due to a water discount is little to none. However, less water will mean less initial volume.

  35. I’ve been using Soapcalc and was wondering if I put 33 percent as the lye concentration will I still have to do the above math? I seriously suck at math and need all the help I can get.

    1. Hey, Sola,
      You can totally use SoapCalc to save you time on the calculations. Knowing how different lye solution strengths influence your soap will be helpful whether you do the figures or leave it up to the calculator.

  36. Love this post! Kenna, you are the QUEEN OF DETAILS!!! I love that because I’m a detail person too. I have one question you may or may not be able to answer. When I entered the same exact recipe in Brambleberry’s lye calculator and SoapCalc’s, I got two different lye amounts. Why would that be? Same oils and weight of oils, same superfat percentage and they both gave me the same water amount. It’s kind of scary to not know how much lye to use. It is a difference of 2.55 grams in a recipe using 1531 grams of oil.

    1. Hey, Maralee,
      Each type of oil actually has a range of possible SAP values. Coconut oil has a SAP range of 250-265 for example. So, the batch of coconut oil you buy today may actually have a different SAP value on the spec sheet than the lot you bought 3 months ago. However, refiguring your recipe each time you switch to a new batch of oil would be super time-consuming.

      So, lye calculators are programmed with an average SAP value for each oil, but depending on the oils sampled, the average they come up with might be slightly different for each calculator. Meaning the same recipe variables will call for slightly different amounts of lye.

      Another issue that might come into play is what percentage of lye purity the calculator is set for. Food grade lye has a slightly higher percent of purity than technical grade lye. If the calculator you are using doesn’t disclose the percentage of purity they are using to calculate, you may want to ask. In my experience, most use tech grade, since it is most widely marketed to soapers.

      That said, both of these issues make a rather small difference in the end product. The 2.55 grams, more or less in your own recipe is not going to make or break it.

      Hope that helps!

  37. Am a first timer and i use this recipe and i got a devastating result
    6.4 oz Palm kernel oil
    3.8 oz coconut oil
    3.8 oz Shea butter oil
    5.09 oz water
    2.51 oz sodium hydroxide
    0.5 fragrance
    Immediately i got my medium trace everything just solidify before i could even pour. Please correct me and advice me

  38. No.It has a big impact on your receipe.It happens to me the same.I used soap calc and i made exactly as it said there.My soap was heavy lye in the end.I wondered why???i used the bramberry calc and surprise!!! THE AMMOUNT OF LYE WAS DECREASED WITH 4 GRAMS FOR THE SAME RECEIPE!!! THE SAME OILS!
    I am afraid to use soap calc now!
    For the second soap i used the same receipe,same oils with bramberry calc and my soap is not heavy lye!
    It makes a huge difference what soap calc you use!
    An extra lye can create a bad soap.
    Now i am using soap calc for the extra information they give,but i use the lye ammount bramberry gives!
    So,when I make soap I have 2 sheets of paper in front of my eyes!
    Yes.Some grams of extra lye makes a huge difference.Example my heavy soap using soap calc.
    People must know.

    1. Hey, Adriana,
      Despite the way we talk about types of oil having a SAP value, in actuality, every batch of any oil will have it’s own SAP value. There isn’t usually a ton of variation, but oils come from plants and animals so, they are affected by weather, region, diet, etc. So, calculator creators take average figures and use those to calculate the SAP of your oil blend. And some even allow user entered info. That’s why values can vary. Usually, an average superfat provides plenty of buffer.

      I’ve used Soap Calc for about 20 years and consider it a great tool. But, there is no harm in double checking. Whether four grams of lye is a big difference depends on your recipe size. So, I would also make sure you check out that batch record and make sure your scale was recently calibrated if your soap tested lye heavy, just to be sure there isn’t something else going on.

  39. It was back in 2016-2017, when you still offered your formulating class that I first fell in love with this explanation! I love that it’s on the website and I can easily pull it up when needed. I still refer other soap makers to it whenever the questions about water discount and lye solutions come up. I normally use anywhere between a 36% and 38% lye-solution when making my Cold Process soaps, depending on how my fragrances tend to behave lower % with accelerators and higher % with well-behaving).

    But this week this article came in particularly handy. I missed a deadline I needed to meet to make CP bars for an upcoming Bridal Shower next weekend. I decided to do the bars using the Countertop Fluid Hot Process Method so they would be done on time. Using the chart, I did an initial 40% lye solution. I didn’t want to go higher than that due to the danger of increased volcano activity. After initially blending and barely getting to applesauce stage, I added more hot distilled water to bring the solution down to a 38%. The reason was to get the “cook” going faster. For me this worked out really well, as in within a minute or two! (PS: I PH test my bars with an Apera meter and cook it to a 9.5-ish). After getting down to 180*F post-cook, I was able to add all my additives and FO’s without burning anything off, AND POUR, not scoop, my soap into the mold. These bars turned out very smooth, not rustic, like the bride-to-be wanted them. 🙂

    38% lye solution was desired to unmold the bars and get them cured out faster (using a fan and dehumidifier) before I package them. 40% lye solution though, with the countertop fluid hot process method, was intense to watch how fast everything came together though! Amazing the difference you see in that 2% during a hot process in comparison to cold process!

  40. Iv Used a lye solution of 30% in my soap so far. will this still cure at the 4-6 weeks? Is there a way for me to cure the soap faster?

    1. Ally, as noted in the article, a stronger lye solution will speed cure. How fast your soap will cure depends on formulation (including lye solution strength but also fatty acid profile, etc.) and your curing environment (soap cures faster with a dehumidifier in the room, for example.)

  41. This post made it a lot easier to understand water discounts, so thank you! But one thing I am still a bit confused about… when other websites/references/soapers mention something like a “10% water discount”. What are they referring to? What are they discounting from? Is it 10% from the “full water” ratio (25%:75%) resulting in 35:65, or do they mean, 10% reduction of the water AFTER establishing the ration. E.g. using a 33:67 ratio, and then discounting the water 10% from there?

    Not many places use that terminology that I can find but it’s still really vague.

    1. Hey, Jessica,
      Those vague, ambiguous references are exactly why we wrote this article. When I’ve seen this in the past and looked at the context, I think it means your first example, 10% from the “full water” ratio. However, I can’t guarantee it. Nor am I confident it is always used the same way.

      Frustrating, right? But that’s why we want to educate soapers about lye solution strength, so we can all speak the same language.

  42. Thank you so much for the article. What is the best Lye solution to work with when you are doing drop swirls with TD, that would be best to prevent glycerin rivers.

  43. HI,

    i just want to say thank you SO much for all the info on these pages.
    i have been making soap for quite some time now but havent learned as much anywere as i did here.
    i have run every recipe i have through soapcal as i used to use a different calculator and i was shocked at some of them regarding cleansing and conditioning numbers although they seemd fine. when i made them with the new % they were even better. This all makes me so much more confident in creating my own recipe”S!
    regarding the water/lye i have still a question just to make sure i get it 100% (as english isnt my native laguage either lol)
    to set that in soap call i just check the box “lye concentration %” right?

    Thanx so much once again i am SO glad i found this page <3

    Mirjam from Holland

  44. hi, if i wanted to ratio, what ration is it for plain simple CP soap using basic oil? I tried using 38% water of oil and my soap ALWAYS stuck in the silicone mold. and it is super soft even after 2 weeks. and what ratio is best for luqid soapmaking? thanks

    1. We recommend a 40% lye solution as the highest water discount, Tami. If that still leaves you with soft soap, I would check into other factors.

      Have you:
      Calibrated your scale?
      Purchased quality, unadulterated oils?
      Checked your recipe for accuracy and used a checklist while making?
      Formulated to include plenty of saturated fats?
      Used relatively high temps and forced gel?
      Provided a low humidity environment for the soap after pour?
      Tried hardening additives?

  45. As a retired lab scientist and fairly newbie soaper, the biggest stumbling blocks for me in my journey were the terms water (and lye) discount and water as a percentage of oils. Discounting I finally figured out meant deducting, but discounting from what? And why did anyone care what the % of water to oils was as stand-alone ingredients? The water really can’t be separate from the NaOH when calculating recipes. In my lab calculations were always based on NaOH solution strength or the ratio of NaOH:water which are really the same thing. If less NaOH was required it was not a water discount but rather a weaker solution.
    Also I cringed every time I saw the term “lye”; such a scary word! Plus it was used interchangeably for the dry ingredient as well as the solution.
    Not meaning to come across as a Debbie-Downer but I keep seeing these terms confusing lots of new soapers. Kenna did a splendid job explaining the some of the chemistry of recipe making in a clear, practical way. She’s an awesome teacher!!

    1. Hey, Debbie!
      Oh my goodness, I kept nodding along with your comment. This article has done so much to demystify lye solution strength for the soapmaking community. Here’s to a new standard (that actually makes sense)!

  46. So, when using soap calc, the lye concentration option is the percentage of the lye in the lye solution?
    EX. In the 33% lye solution with 67% water my lye concentration will be 33%?

  47. Hai everyone im just the beginner. I never learn before, only watch youtube and youtube, just make may own calculating based on what i watched, and im just curious and tell me if im wrong. (I know i am wrong, but i dont know which part? Because when i finish blend the oil and lye, i have plan colouring my butter into 3part colour, i starting colouring & pouring to the mold, and 15minutes when i want use my rest butter, the butter really thick :((
    I know i make a mistake but i dont get it

    Ok I used:
    – olive oil :400gr
    – castor oil :132gr
    – avocado oil : 93gr
    – canola oil : 125gr
    Total oil: 750gr

    Distille water : 285gr (38% from total oil)

    Sodium Hydroxide: 105gr (37% from total Distille water)

    Please tell me , thank u so much

  48. Thank you for explaining the lye. I am new to soap making and I could not figure out how everyone was making the own recipes. I really understand it now. Thank you for posting this. I am no longer lost.

  49. Since reading your awesome post, I’ve switched to a 33% lye solution and I’m loving the results. I now want to make a CP soap with added hones (about 1 – 1.5 tbsp/pound). Where I’m confused is in how to adjust the lye percentage to stop the honey from heating up the batch. I also use the heat transfer method to melt my hard oils, so I would be adding the honey after the liquid oils.
    If I’m understanding this correctly I should drop my lye solution percentage to increase the water to hopefully avoid a problem. Is this correct? I was thinkg about a 28 or 30% lye solution for this batch.

  50. Hi there,

    I was thinking of making my lye solution in advance. But I don’t understand the water discount so goats milk can be added to the oil so it doesn’t scorch. I have a couple questions:
    1. What percentage do I need of goats milk to be really be goats milk soap?
    2. How long with the 50/50-(water/lye) last before it doesn’t work as it should?
    3. If I use a 50/50 to pre mix for my lye solution, do I only use 10-15% of goats milk (or other liquid) to create a goatsmilk soap, into the
    oils later?
    Thank You,

    1. 1. Not sure where you are, Christine, but if you are in the USA there are prohibitions against using an ingredient name in your product name, fyi. Those vary depending on product classification (soap, cosmetic, and/or drug). So, you probably really shouldn’t call your product “Goat Milk Soap”, and there is no standard for what constitutes a “real” goat milk soap. You can make marketing statements that include references to your ingredients, but, you are not allowed to mislead customers.
      2. Shelf life is indefinite, dependent on the expiration date of your components, and subject to storage conditions. Best practice is to adopt the use by date that is earliest, either your distilled water or your lye, and to store in an air-tight container that can withstand strong bases. And, really, who wants to store a ton of lye solution for months?
      3.You need to add enough additional liquid to create the solution strength you want to work with. That additional liquid can be water and milk or just milk.

  51. I love reading your articles!!! So helpful!!! I’m just curious as what the lye to water ratio should be for liquid soaps with KOH? I’ve ran the same recipe through three diff calculators… soap calc, Sage, soap making friend) and the lye amount varied 10g and the water varied 22g?

  52. I’ve read this a few times in order to fully grasp it (I’m rather math-adverse), and I think it’s really starting to click. Thank you so much for taking the time to explain. I’ve watched so many vids and read books and blogs and not many go into this for whatever reason, but it really is so important. I really want to understand the process and this helps immensely.

  53. Not a math head – having trouble getting the calculation. When I work the calculation above, I do not get the 5.625 – I get something way out of line! I get the 3.51, the .40 X .60 = .24 then I’m lost or I’ve done it wrong! Help – Ihave recipes that I’ve made in the past with the help of a seasoned soapmaker, but I’d love to figure this out on my own!

    1. Hi Lisa
      This is the way I calculated and I got the results right:

      This is the formula: Amount of Lye / Desired Solution Strength x (100% – Desired Solution Strength) = Water Amount

      Let’s say that you need 3.51 ounces of lye and want to use a 40% lye solution:
      3.51 ounces of Lye / 40% Lye Solution x (100% – 40% Lye Solution) = Water Amount
      3.51 / 40 x 60 = 5.265 ounces of Water

      3.51 / 0.40 = 8.775
      8.775 x (100%-40%) = 8.775 x 0.60 = 5.265

      I hope it helps.

  54. Great article! Thanks for creating something that is timeless. In reference to the a discount of 35-44%, What would be the cure time for this? Is there a way to formula cure times based off of the amount of lye discount that you use?

    1. Cure time will vary based on your curing environment and formula. Weighing (to establish when evaporation is complete) and testing your soap at intervals for quality and longevity will help you decide when it’s cured.

  55. THANK YOU so much for this article. Being someone fairly new to soapmaking, this has helped me understand things better. My question is, when doing a lye discount such as 33% will this result in an overall harder bar that will last longer. Longevity? I use OO at 50%.

    1. Hi Carrie! While a lye discount will make your bar harder more quickly and easier to unmold, the ultimate longevity of your soap comes down to your overall recipe.

  56. I know I’m several years late to the party but this is just what I need. Thank you.

    Also, a few quick questions: In your avocado example, you can count the puree as all water even though avocado has so much fat in it?

    If I use water to disperse colorants, would I need to subtract that from the lye solution if I want to maintain my water discount? What if I use oil to disperse? Would I subtract that from the amount of oils in the soap recipe?

    1. You’re never too late to the party! The Modern Soapmaking party never stops.

      Yup, if you’re using extra water or oil to disperse colorants you’ll need to subtract that from your totals. And yes, you can count the avocado as water! Think of goat’s milk soaps – they substitute goat’s milk for water, which has loads of lovely fats.

  57. Can there be differing strengths of lye?? I have been using the same recipe for 3 years – 3oz lye and 6.5oz goat milk. I have never had any issues with it but this month it is tracing very quickly and the first batch seized up on me before I could get it in the mold. Thinking I had miss measured I made 3 more batches with the same results. When I cut them 2 days later they are still soft and sticky on the inside. I used the same brand of lye I normally use but opened a new container this month. I can’t figure out why this soap is coming out so much different than any other soap I’ve made. Thanks for any insight

    1. If you’re getting your lye from the same supplier, you should not be experiencing a difference. It might be worth contacting your lye supplier about this batch. – Rachel

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