How to Make Castile Soap

You either hate it or you love it.  Castile.  I used to be on the “hate it” team.  But I never tried an aged…well cured bar of castile.  Now I’m on the “love it” team!

To me castile means a soap made out of olive oil only (+lye and water).  I know to some…castile is a soap made with “mostly” olive oil and can contain other vegetable oils.  I make my castile with no added color or fragrance.  It’s just a beautiful cream colored bar of soap.  I let mine cure for at least four months.

Let’s make some castile.

The recipe is simple.  100% olive oil.  So determine how many ounces of oils your mold holds and go with that.  My mold holds 48 oz of oil.  I like to do a 5% superfat with castile so that will give me 6.2 oz lye for 48 oz of oil.  I take a steeeeeeeep water discount when making castile.  I usually multiply my lye amount by 1.1 to get my water amount.  Since my recipe calls for 6.2 oz of lye, I’ll use 6.8 oz of water.

*Please note that doing such a high water discount makes your lye solution much more potent and dangerous if splashed on you.  Wear gloves, goggles, shoes and long sleeves to help protect against splashes.  Since your solution if much more concentrated make sure that the lye crystals are completely dissolved before adding to your oils.

For all my soaps I use Soapers Choice Refined A Olive Oil.  I personally don’t like pomace olive oil in soap; other soap makers use it. Olive oil is traditionally slow to trace but with such a steep water discount…it won’t take long at all to trace.

To start.  Make your lye solution.  Let it cool down a bit to 90-100 degrees F.

Measure out your olive oil.  I leave it at room temp…I don’t worry about heating it up or making it the same temp as the lye solution.

Add your lye solution carefully to the olive oil.  Be careful with splashes!

Stickblend until your soap reaches trace.

I like to let it sit for a minute or two before pouring it into the mold.  Olive oil can sometimes seem like it is well emulsified and then all of the sudden separate.  So after you think you’ve reached trace…let it sit for a minute.  It’s not going to thicken up or seize on you so you can take your time to make sure it’s properly mixed.  I love reaching trace and then lazily mixing by hand with a spatula.  It’s a bit soothing and somewhat hypnotic.  🙂

Pour it into your mold.

Cover and insulate as usual.  Since we’re using such a high water discount…your soap will probably not gel.  No worries though…this soap is rock hard after about 2 days in the mold.  Normally we think…high olive- must not cut right away.  But you’ll find that this is super hard after a day or two and ready to cut.

Be sure to cure your castile in a cool dry place without the bars touching (as that can trap moisture).  Cure them for at least four months.  The longer the better!

So…if you haven’t given castile a try…give it a go!  Or maybe you’ve tried it and hated it.  Try it again!  The high water discount and a long cure make for a really nice bar of soap.

Good luck!


About the Author:

I am a soapmaker, author and blogger! I started blogging in 2008, sharing soap recipes, design tutorials and publishing articles on various topics of soapmaking.


  1. Christine September 5, 2018 at 1:58 am - Reply

    This is creamy. I will make one. But can you help to make dish wash bars. Do you have to use caustic soda ???

  2. emme smith July 1, 2018 at 3:05 pm - Reply

    Love the recipe – I added a few ounces of castor oil to increase the suds. The soap was rock hard in just over 24 hours. A little difficult to cut. The soap is just beautiful, so smooth and it feels as it would have a nice slick feel for bathing. We have friends who are allergic to almost everything and they feel like this soap with no fragrance or color will be just perfect!

  3. Aide Mancera February 27, 2018 at 11:14 am - Reply

    Hello Amanda, I am new at soap making… So I am reading and reading all the tips and ideas… sorry about my ignorance… what is the difference between a castil soap and the others cold process soaps? What make you choose between each one? Thank you.

  4. Cindy E January 1, 2018 at 1:01 pm - Reply

    Okay, so I am green, very green – my 2 pound mold hasn’t even arrived yet! Your post was great on figuring out how much lye and water to use with Olive Oil to make castile soap. What I’m still uncertain about is how much oil(s) to use. If my mold is 2 pounds do I assume that I use 32 oz of OO? Do I subtract the amount of lye/water that goes into the OO to make the total amount 32 oz? Just want to get a recipe right and not waste everything and start out discouraged. I’m excited to start but don’t want to foul everything up. How much OO do I use for a 2 pound mold? Thanks so much!!!

  5. nike June 23, 2017 at 10:28 pm - Reply

    hi Amanda, love your post.May i know if all castile soap color must be creamy white?i have used 100% extra virgin olive oil and my soap color is creamy but light brown instead of white. is it because of my extra virgin oil is not pure? i have tried another brand of extra virgin oil and the color is creamy white.

  6. Nancy Cannoy May 22, 2017 at 1:44 pm - Reply

    Love your soap. I have been wanting a good castile recipe. Tried yours today and used olive pumice. OMG what a quick trace. I keep stiring ( It didn’t want to) but I finally plopped it in mold. Plopped and begged is more like it. Hope it works.

  7. DS May 3, 2017 at 8:43 am - Reply

    Hi there! What is the size of your soap mold?

  8. Stephanie Wilson April 23, 2017 at 10:11 am - Reply

    Quick question about Castile Soap. I typically put Kaolin Clay in my soap batches. Would adding 2 tbsp of K. Clay benefit Castile soap?

  9. Sylvia March 6, 2017 at 10:31 am - Reply

    Hi Amanda,

    I am fairly new to this, could you tell me if your 5% super fat is already included or should I add after oil is mixed with lye. I always get confused with this part.

    • Amanda Gail March 6, 2017 at 4:08 pm - Reply

      Hello! The superfat is already included in this recipe… 🙂


      • Karley March 6, 2017 at 9:53 pm - Reply

        What is a high water diccount? Does that just mean you use less water?

        Why do you use this method with this recipe?

    • GAil March 22, 2017 at 7:52 am - Reply

      You said the super fat is included in the recipe, however, all I see is olive oil. What is the super fat used and how much?

      • bansel July 30, 2017 at 12:42 am - Reply

        Hi ! I try to explain.when we make soap we calculate the iye quantity according to how much oil we used.iye turns the oil to soap .if you decrease the iye quantity it makes soap but there will be some oil that cant become soap.the oil in the soap at the end means super fat.this castile soap includes %5 super fat (so it means iye discount for leaving some oil in the soap)this oil is important for moisturizing.I hope I am not wrong and could explain with my little English 😊

  10. Brenda February 6, 2017 at 8:47 pm - Reply

    Hello Everyone!!!
    I’m hoping you might be able to help me out!! I trying to find a Canadian store with reasonable shipping prices as I’d like to purchase some M&P soap base,,,what’s the best site to buy some

  11. Cindy May 17, 2016 at 7:53 am - Reply

    Wow, did my castille attempt ever accelerate! Totally surprised me and left no swirl opportunity. I’m guessing the culprit was a combo of the 1:1 lye/water ratio PLUS me subbing in 1/2 of the water with aloe. (the Wasabi f.o. I used doesn’t usually misbehave.) Still excited to see how this batch turns out, but if I do use aloe again, I will also use more water to lye. And my next batch of Castille will not have anything but oo, water, lye — as usual, I should have tried the recipe as written before messing with it 🙂

    Anyway, thank you very much for this tutorial because I have always wanted to try castille.

  12. Karen May 16, 2016 at 2:08 am - Reply

    Hi there – your castile loooks great! I’ve been making castile for years. As well as a few other unscented bars. I’ve been curious about water discounting because of the orange spots that I get sometimes. Does the water discount help with this?

  13. Margo Long January 20, 2016 at 1:57 pm - Reply

    Thank you Amanda Gail for this great information. I made a batch of the Castile soap a few days ago and everything went well. I used a 55% Water to the lye instead of the 50/50 ratio and put the soap in a warm oven with the heat turned off and the oven light left on. Unmold the next morning and that evening when I went to but the soap using my Tank cutter I could barely get the guitar strings through the soap. Is that normal for it to be that hard to cut?

  14. Jay December 18, 2015 at 5:00 am - Reply

    How many bars of castile soap do you make with 48 oz of oil and how much is the approx weight of each bar? I want to try this.

  15. Brenda April 30, 2011 at 7:38 pm - Reply

    Okay, I’m going to try it again. I didn’t let mine cure long enough and I’m inspired to do it again. I better get soaping! Thanks for the article!

  16. Sieglinde March 22, 2011 at 8:08 pm - Reply

    I made castile soap 6 months ago and you are right. The longer it cures the better it is. We just started using a bar of it and it lathered up great and held the mild fragrance oil I used in it equally great.

  17. iheartsoap March 15, 2011 at 9:30 pm - Reply

    Awesome! The blend sounds amazing. I can’t wait to see the blog post! Thanks for posting all that info. I haven’t tried pomace olive oil yet. That’s interesting about it moving so fast!

  18. Celine Blacow March 15, 2011 at 5:25 pm - Reply

    Ok I made it! I used the same quantity of lye as water (ran it all through Soap Calc first, just to be sure). I used Olive Pomace because it’s what I had most of.

    I did fragrance with a blend of Sweet Orange, May Chang, Lavender, Patchouli, Geranium & Ylang Ylang – divine!

    I was stick blending just fine and I tend to err on the side of caution and maybe SB’d it a little too much and it got very thick and puddingy in texture (like the creamiest nicest pudding you’ve ever seen). I plopped it all into my mould and banged it like crazy to get it all to settle and have no air bubbles.

    Things to note:
    I used some TD because my pomace is a yucky green and I don’t like it much so I wanted to tone it down. However, when I added the lye water (with silk added btw) it changed the oils (with TD) from a creamy green to a beigey/creamy colour!

    It’s heated up like crazy! I shoved it in the fridge an hour and a half ago and the bottom of it is still very hot.

    Pomace does speed trace so maybe I shouldn’t have used such a steep discount or should have used a Golden Olive oil but I hadn’t enough in the house.

    To answer my previous question, my mould managed 1kg of oils/butters and, for this, I made 1.2kg of oil and it’s fit just fine so yes, reducing the water level will reduce the size in your mould.

    So the soap is now in the fridge and I’ll leave it there all night – I suspect it will, at least, partially gel. It smells amazing though – think this is the most intriciate EO blend I’ve ever used.

    I’ll post pics on my blog tomorrow so you can see. Cheers x

    • Trish August 2, 2016 at 6:12 pm - Reply

      hi… i know this post was way back 2011 but i am still hopeful that i will get a response from you.
      May i know the ratio you used when you mixed Sweet Orange, May Chang, Lavender, Patchouli, Geranium & Ylang Ylang for your Castile soap?
      I was intrigued when you mentioned that it smell divine! i am new in soap making and just attending a few seminars on how to do it but i haven’t
      tried making my own yet as i wanted to gain more informations more before doing so.

      I hope you don’t mind sharing it with me… 🙂 thank you in a advance! 🙂

  19. Celine Blacow March 15, 2011 at 10:00 am - Reply

    One thing I was just thinking about the water discount … does this mean that my bar size will be smaller given the quantity of liquid (lye water & oils) would be less as there is less water? (sorry if this is a stupid question). I wanted my bars to be the same size so perhaps I should up my oil amount (with the corresponding increase in water & lye of course) to allow for this…. is this making sense??

    • iheartsoap March 15, 2011 at 10:07 am - Reply

      You know…I’m not sure. In theory…you’re using the same amount of oils as your regular batches. The only difference is that there will be less shrinkage during cure for the castile because you start off with less water in the beginning. If that makes sense. But it wouldn’t hurt to make your batch a bit bigger.

  20. Carol March 14, 2011 at 9:06 pm - Reply

    Love Castile.

  21. Patrice March 14, 2011 at 7:43 pm - Reply

    your bars look fantastic a! i love how white they got, and you’re using pure olive oil which has a green tint! a four-month cure?! i am way too impatient for that. have you ever done a hot processed castile soap?

    • iheartsoap March 14, 2011 at 7:55 pm - Reply

      Thanks, Patrice! You know…I’ve never hot processed a castile batch. I did a quick google and it looks like some people do it that way…

  22. iheartsoap March 14, 2011 at 5:39 pm - Reply

    :). Let me know how it goes!

  23. Celine Blacow March 14, 2011 at 4:59 pm - Reply

    Ah God, you did a whole blog post for me??? I’m stunned!!! Yay!!!! I’m so making a Castille soap in your honour this weekend!!! I have to scent it though, can’t not … will you forgive me?

    A blog post for me… stunned!

  24. iheartsoap March 14, 2011 at 3:52 pm - Reply


    I read about the water discounting effecting gel in Kevin Dunns new book. The less water you use the less likely for gel to occur (the harder you have to force it) and the more water you use the easier to gel. It’s a great book with great info. I highly recommend it.

  25. Stephanie March 14, 2011 at 3:49 pm - Reply

    oh wow! I had no idea that the water discount effected gel! if you could elaborate I would really appreciate it!! I started water discounting the same time I started using colorants.. and I thought that maybe they were constantly preventing gel.. I even started oven processing and letting it get WAY to hot and not seeing much gel.. the soap got super hard anyway, but it was still weird to me!

  26. Holly March 14, 2011 at 3:10 pm - Reply

    Castile soap is awesome…with the proper cure like you said. I’m going to be making some soon for use next winter! A soaping friend recommends making castile with a fun summer scent so you can have a touch of summer in the worst part of winter. 🙂

  27. Stacey March 14, 2011 at 2:49 pm - Reply

    OOooo! I didn’t know about the steeep water discount! I stupidly mixed up a master batch of lye at a 50:50 ratio and am now afraid to use it. I tried it once and screwed it up royally. NOW I know what to do with it! Thanks Amanda! Castille soap, here I come!

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