How to Make Soleseife a Natural Seawater Soap Recipe

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Would you like to create smooth, hard, and easy-to-un-mold soap every time? Then I recommend that you try this soleseife soap recipe. It’s a soapmaking technique that uses salt water to help harden soap quicker, even if they’re made of pure olive oil!

How to make Soleseife: a Natural Sea Water Soap Recipe

There are two main ways to make soleseife soap, with homemade brine or you can make natural seawater soap. Saltwater soap is smooth, hard, and easier to get out of soap molds, so can be a useful technique for softer soap recipes. You can convert many cold process soap recipes into a soleseife recipe just by replacing the water used for the lye solution with salt water.

This soleseife soap recipe will walk you through making a small batch of pure white seawater soap. However, feel free to use salt water or brine in almost any soap recipe that you hope to make harder quicker. It’s particularly useful for recipes with high percentages of soft oils such as tallow or olive oil. If you use seawater or brine when making Castile soap, it effectively turns it into Castile brine soap.

Make this Soleseife soap recipe with seawater to create smooth, hard, and easy to un-mold bars. Use water collected from the beach or homemade salty brine to make natural seawater soap #soaprecipe #saltsoap #saltbar

Benefits of Soleseife Soap

Soleseife is simply the German name for soap that you make with salty brine. This type of soap was invented there, so we continue to call it by that name. It’s not the kind of soap that has actual pieces of salt in it (see this salt soap recipe) but soap that’s made with a lye solution created with brine instead of water.

There are a few reasons that you’d use brine in soap recipes, but the most useful is that it hardens bars quicker. Some soap recipes are soft and sticky at first and often difficult to get out of the molds. Adding salt can harden fresh soap quicker, making popping it out of molds a lot easier. It’s the reason that you often see sodium lactate suggested as a soap hardener, too (salt = sodium chloride).

How to make Soleseife: a Natural Sea Water Soap Recipe
Soleseife soap is made with dissolved salt that helps harden the bars

Even though seawater and salt brine as a water replacement can help harden soap initially, it only speeds up the natural process of hardening. This means that your final sea salt soaps will not be any harder than they’d be than if you left the salt out.

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Salt is Good for Your Skin

Another reason to add salt to soap is for skin therapy. Sea salt is beneficial for the skin since it helps balance oil production and controls bacteria. Both reasons make it a great addition to soap and skin care products for acne. It’s great for any skin type, though.

How to make Soleseife: a Natural Sea Water Soap Recipe
A little salt can be beneficial to soap recipes, but too much can reduce the lather

Another thing that I love about making seawater soap is that you can collect it yourself if you live near the beach. That makes it extra special and local, but just ensure it’s clean water and not polluted. You’ll also see in the recipe that the amount of salt in seawater is great for soleseife, but the amount of salt you use can go up to 25% salinity.

Customizing this Soleseife Soap Recipe

Practically any cold process soap recipe can be converted into a soleseife soap by replacing the distilled water with seawater or brine. It can be a full replacement or just a partial replacement, in case you wanted to also add other liquids such as goat milk. Although this recipe is basic and pure white, you could also naturally color the bars using clays, botanicals, or other colorants.

You can make a salt brine in place of seawater using bagged sea salt

There’s much to be said for a simple unscented bar of soap, but many people prefer soap that smells nice. I’ve included just one essential oil in this recipe, but you could use a different type or create an essential oil blend such as peppermint, lemongrass, and lavender. I have a guide to how to work out how much essential oil to use in soap recipes here.

Curing Soleseife Soap

Salt can help speed up the curing process by drying the soaps out quicker. However, I recommend you still cure the soap for at least four weeks. Curing is more than about saponification and water loss. It’s also important to cure soap to help it develop a crystalline structure that leads to gentle cleansing and a fluffy lather. This recipe is also high in olive oil, and the longer you give it to cure, the better the soap will be.

Soleseife soap needs a regular curing period

You can use your handmade soleseife soap immediately after the curing time is up. Take a soap bar in your hand, lather it up, and enjoy its gentle cleansing power! The shelf-life completely depends on the closest expiration date of the materials you used to make it. If the olive oil you used has an expiration date of next month, then that’s your soap’s best-by date. Use it quickly! It’s far better to use oils and ingredients that aren’t about to go rancid, though, so keep an eye on the best-by dates.

More Soap Ideas and Recipes for you

Soleseife Soap Recipe: Natural Seawater Soap

Lovely Greens
1lb (454 g) Soleseife soap recipe creates six bars of hard, white seawater soap. It has a 6.5% superfat, a 33% lye concentration, and the final lather is creamy and the bubbles fluffy and stable. There is no scent of seawater in the soap if you choose to make your soap unscented.
5 from 2 votes
Prep Time 30 minutes
Cook Time 30 minutes
Curing time 28 days
Total Time 28 days 1 hour
Servings 6 bars


Lye solution

Soaping Oils

After Trace


Soap Making Preparation

  • Ensure that your soapmaking station is set up with all of the equipment, materials, and tools you need. Pre-measure the main ingredients using a digital scale. The coconut oil into a stainless steel pan, the liquid oils together in a jug, the shea butter in a microwaveable dish, and the lye (sodium hydroxide) into a dish. Take care to wear gloves when measuring the lye.

Prepare the Seawater or Brine

  • You can either collect your own seawater or make brine, it's up to you. Seawater soap will be made with water with a 3.5% salinity but when you make your own brine you can create a solution of up to 25% salt. The term soleseife can be used for soap made with seawater or your own homemade salt brine.
  • If you've collected your own seawater from the ocean, let it settle for at least an hour so that any sand or particles have a chance to settle. Gently pour it through a sieve, trying to keep the settled sediment (if any) in the original jug. Measure out the amount you need for this recipe into a heat-proof jug.
  • To make a brine with the same salinity of seawater, measure 4.38 g (0.08 oz) fine grain sea salt into 121 g (4.27 oz) hot distilled water. Stir until dissolved and allow to cool to room temperature. Create a stronger brine by adding more salt. Measure it out precisely though and don't go over a 25% salinity. If you do, it's possible that your soap will turn out crumbly, or have poor lathering properties.

Make the Lye Solution

  • For full information on soap-making safety and equipment please head over here. It’s important to read it before trying to make soap the first time. Put on your rubber gloves and eye protection (goggles) and set yourself up in an area with good ventilation. Under a hob, on the doorstep, or outdoors is perfect. Pour the sodium hydroxide into the seawater/brine and stir with a stainless steel spoon. Be careful not to breathe in the fumes. 
  • Stir well and leave someplace safe to cool to 100°F (38°C). I tend to set the jug containing the lye solution in cold water in the sink.

Melt the Coconut Oil

  • Heat the coconut oil on the hob over low heat until it's completely melted. It will melt quickly so do not leave it unattended.
  • When melted, take the pan off the heat and cool on a potholder. Stir in the castor and olive oils and continue to stir every few minutes until the oils have cooled to 100°F (38°C).
  • You also need to keep an eye on the lye solution, stirring occasionally, and cool it to around the same temperature.

Melt the Shea Butter

  • Melt the shea butter in preparation for step six. You can either do this in the microwave or on the stovetop. In a microwave heat for 15 seconds at a time and stir; repeat until liquid. On the stovetop, you can heat on very low heat in a small saucepan. Don't take your eyes off it until it's fully melted though since it can go from melted to sizzling hot in a heartbeat. When the oil is melted, set it aside from the heat and move on to the next step.

Make Coconut Oil Soap

  • Get the soap mold prepared and double-check that your goggles and gloves are on and that you won't be disturbed for the next ten minutes.
  • When the lye solution and oils are both about 100°F (38°C), pour the lye solution into the pan of oils. Pour the lye solution against a spoon held in the oils as this will reduce air bubbles in your final bars.
  • Using the stick blender turned off, stir the pot of oils and lye solution together. Next, place the head of the stick blender against the bottom of the pot in the center of the pan. Turn it on and pulse for a few seconds and then turn it off and use the stick blender as a spoon to stir the mix together. When the stick blender is on, it's far better to keep it in one stationary place. Moving it around for small batches can create a mess, depending on how large your pan is.
  • You'll continue pulsing and stirring until the batter hits a light trace. This is when the soap begins to thicken slightly to the consistency of warm custard. If you take the stick blender out and dribble the soap batter into the pan, the dribbles will create a texture on the surface.

Add the Shea Butter and Essential Oil

  • When the soap batter is at 'trace', you can stir in the melted shea butter and optional essential oil. Peppermint essential oil will give your soap a zingy scent and feeling and it's also great for oily skin. It's optional though and you can make this recipe without it for a mild unscented bar.

Mold the Soleseife Soap

  • When the extras are mixed in, pour the soap into your mold(s). If you're using the cavity mold that I've used then you can pour the soap batter in and leave it uncovered on the counter to harden up for a day.
  • If you're pouring your soap into a loaf mold like this one, I recommend placing it in the fridge to cool and harden. This will help ensure that the bars are pure white all of the way through. If you don't refrigerate it, there's a chance that there will be a circle of slightly darker (gelled) soap in your bars. If this does happen, it's just cosmetic and the soap will be completely fine.

Cut and Cure your Seawater Soap

  • I recommend taking soleseife soap out of the molds after 24 hours and it should pop out pretty easily. Cut your bars if they were in a loaf mold and it's best to wear gloves when handling soap at this point. Most of the saponification is complete but there may still be a tiny amount of lye in the soap. Plus fingerprints.
  • Now place your soleseife bars spaced out on a sheet of wax paper in an airy place out of direct sunlight. Leave them there to cure for a month. During the curing process, the bars will harden, lose water, finish saponifying, and develop that all-important crystalline structure. More information on curing is here.
  • At the end of the cure time, these soaps will be hard and white. For full instructions on how to cure handmade soap head over here
  • Once made, your soap will have a shelf-life of up to two years. Check the coconut oil best-by date though, since that will be your soap's best-by date too!


Lastly, are you a beginner soapmaker looking for more guidance on how to make handmade soap? Enroll in the Natural Soapmaking for Beginners Online Course to get up to speed quickly. You’ll learn all about soap ingredients and equipment and be guided through step-by-step soap recipe videos.
Keyword salt, soap, soap recipe
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Recipe Rating


  1. How do you determine the 25% brine?

    Thanks!! I really want to try this, but am a bit confused about the % of brine or salt to water ratio.

    1. Hi Shari, a 25% brine is a liquid made with 25% salt (by weight) and 75% water (by weight). For example, 25g salt and 75g water or 250g salt and 750g water. To make 125g of brine you would need 31g salt and 94g warm water.

  2. Anonymous says:

    Does it smell salty?If no, how do l give it a salty smell?

    1. Salt doesn’t smell like much to me — this recipe doesn’t have a scent other than that of unscented natural soap.

      1. How do l ensure that the water is not polluted?

        1. You will need to do research about where you’re sourcing the seawater. If in doubt, make brine at home using sea salt and distilled water.

          1. If l use epsom salts or pink himalayan salt to make this soap will it have therapeutic properties like the salts?

            1. You cannot make claims that any soap has therapeutic properties because it can’t be proven since there are no studies on it. In the case of salts, including Epsom salt, being that soap washes off the skin it’s unlikely at best.

  3. Could I possibly substitute the castor oil and Shea for another oil & butter?

    1. Hi Lori, soap recipes are chemical formulas and each oil is chosen for a purpose. The lye amount is also exactly what’s needed for these oils and butters and in the precise amounts listed (learn more about customizing a soap recipe). If you’re not as keen on this recipe, find another one that doesn’t include castor oil or shea, like pure coconut oil soap or castile soap. You can make any recipe a soleseife recipe by replacing the water amount with brine/saltwater.

  4. 5 stars
    Thank you for the 1x 2x 3x toggles! I love your soap recipes and info and I’m making soleseife today 🥳

  5. I made this Soleseife soap recipe exactly and added 1 tsp of Spirulina to color it green. I left it to cure now for 7 weeks. It was a lovely color green until about the 5 week mark then it began fading to a slightly light colored beigy green. I had it curing in a cool shaded room the whole time. Can you explain why this would happen?

    1. Hi Amanda, unfortunately, most plant-based green colorants are fugitive in soap. That means that they fade quickly, especially when exposed to light. The one that lasts the longest is Chlorella, though.

  6. 5 stars
    Beautiful white bars with great suds. Thanks for the soap recipe!

  7. Hope this wasn’t already asked!

    If using sea water to make the soap do you have to worry about it causing the soap to smell bad if the soap is unscented?

    Thank you for this wonderful recipe! I’m very excited to make my first batch with sea water! (Hoping to eventually incorporate kelp as well!)

    1. Hi Savannah, I find that fresh sea water doesn’t leave a scent in handmade soap :)

  8. RUTH kape says:

    thank you for the lovely recipe. Can i use regular olive oil instead of pomace and if so do i have to change the lye and water content? thanks

    1. Yes you can and no, you do not change the water and lye amounts :) EVOO is more expensive than pomace and traces slower, but the SAP value and final soap qualities are the same.

  9. Does anyone know if you can use seawater/saltwater in a liquid Castile soap?

  10. I use a 5 lb. mold, do you have the recalculation to make this recipe 3x larger.

    1. Multiply each fat by three and then go to a soap calculator to enter the fat/oil values and it will tell you how much water and lye to use. Choose a 6-7%super fat value for determining your lye amount or whatever you prefer.

    2. Mary, above the ‘Ingredients’ area of the recipe is a toggle. Choose 3x to multiply the soap recipe by 3.

  11. Can seawater be used in a soap recipe where potassium is collected from bananas or other natural resources?

  12. Hi!
    Should I worry at all about sea water that may have elevated marine toxins in it? For example, when our shores are closed for crabbing and clamming due to the toxins, should I not collect water for soap? It is a toxin produced by marine algae so I think it may be different from bacteria, which you mentioned in an earlier comment reply that it would be killed by the lye solution.

    So my question is if I have to worry about Domoic acid, would that affect soap making?

    Maybe it would be weird since it’s an acid? I am super curious about what you think, even if you don’t have a definitive answer! Seems complicated.
    Thank you!

    1. Avoid using any water in a soap recipe if you’re in doubt over water quality.

  13. I have a question, if the water is saturated with salt, will the lye still be able to dissolve?


    1. The brine does not affect the lye’s ability to dissove or react with water.

  14. Hi Tanya,
    What a great post, I’ve learned so much so far with your tutorials and such detailed explanations, thank you very much!
    I’ve tried quite a few of your recipes with much success :)

    Just 2 questions:
    The water you used to produce the salty brine, is it distilled, filtered or regular tap water?
    Would using homemade salty brine or sea water work ok to reduce the unmolding and curing time of Castille soap or other soft soaps such as the one with Carrot purée?

    Thank you very much for your time!

    1. Hi Flor, it’s best to use distilled or filtered water in soap making. Minerals, chlorine, and other things in tap water can affect the shelf life of the soap and how much soap scum it creates.

      Salty brine could theoretically help with other recipes too. The best way to find out, for the recipe you have in mind, is to make a small batch and see :)

  15. Derek Fairley says:

    Hi Tanya,
    I am interested in soap making, but have dexterity issues and as such want to start making soap with Melt and Pour as it would cut out what I term the most “dangerous ” part ie using Lye.
    So now to my question. What parts of your recipe would I need to add to end up with a finished bar of soap.
    Thank you.

  16. christina says:

    Hi Tanya,

    I love your recipes and have made wonderful moisturizing soaps.

    This is the first time i am trying your method of folding in the shea butter at trace. I ran your recipe through soapcalc and noticed that the lye amount was for the full oil amount inclusive of the shea that was mixed at trace.

    With your soleseife recipe, the bars feel so lovely on the skin during shower and my skin did not feel squeeky during the shower, which I love. However, i noticed that my skin got really dry after 5 times of showering.

    I wonder is this perhaps the nature of a soleseife or if it is due to the lye amt? what if i use a lye amount that is just to saponify the oils stated sans shea? would that then be better?

    i would love to hear from you soon <3

  17. I’ve just cut my first salt water (4% salinity) soap and it’s lovely. Thank you very much. Can’t wait for it to cure to try it out.

  18. Is regular ocean water really safe? I live in a beach town with a beach that ranks pretty high in cleanliness, but, what if a fish died and a couple of kids peed while swimming or, i don’t know… I’m probably overthinking it, but there’s a reason we want to shower after going to the beach. Is there a way to check the “purity” of the seawater collected? Thanks for the recipe, can’t wait to try it!

    1. Maggie, I don’t think any bacteria would survive being suspended in a caustic solution. Soap also has a final pH of between 8-11 which is also inhospitable to bacteria. They prefer neutral to slightly acidic whereas soap leans more alkaline. Hope this helps :)

      1. Hey lovelygreen plz say me required ingredients for olive oil soap with salt
        but should i use sea salt or pink himalayan salt which salt because mam i only want to add only 4 ingrdients
        1 olive oil 1000gm
        2 sea salt or pink himalaya salt( which one & how many grams )
        3 lye Gms?
        4 water &(.which water what it should mentioned in water distilled or something)

        Plz reply im trying to get but in youtube i cant find one to make it with salt
        they say u should not add salt
        & i dont want to use coconut oil or any oil just olive not even shea butter just lavender essence & dry rose petals to it

        So plz reply me & tell me how to make it i beg u or anyone plz reply md im new to this im searching from 1/2 year..

  19. Hi Tanya,
    I love your explanations and your videos. Is the soaps are dangerous while it curing? ( I live in a small apartment and there is no other place for curing only our living environment) . Is there any way to know when the soaps completely cured? And how can I know the final soaps ph level? Merci for your answers

    1. They are not dangerous while curing and actually scent your room (or apartment) really nicely during that stage.

      All soap has a final pH of 8-11 but I don’t tend to test them often. The only time I think it’s worth testing pH is if you’re uncertain about the amount of lye in the recipe. Basically, in the case where you’re making it and think you accidentally put in too much. But even then, testing for pH is tricky and often inaccurate and the final pH in many cases will give you a normal pH level even if there’s excess lye in the soap. Also, the pH you get won’t even indicate how mild the soap will be anyway. My advice with testing pH: don’t bother unless you see something weird happening. Meaning liquid oozing from the soap, crystallization, or white clumps.

  20. Wonderful tutorial @Lovelygreens!
    I’ve just made it for the first time with a 20% brine solution Sunday night. I was able to unmold it the next morning. It’s now Wednesday afternoon and the soaps have been in a drying chamber with a dehumidifier set to about 44% humidity. They look really nice!
    I have just a few questions as this is the first soap I’ve ever made if you have a moment…
    1. how soon are the soaps safe to be handled without gloves?
    2. there’s a tiny bit of glycerin sheen on the outside in a few places…ok?
    3. you gave the curing time estimate of 2-3 weeks (with 3 weeks suggested for ‘sea water’). since I’m using a much higher concentration of salt (20%) would you think that 2 weeks would give me a complete/ready to use cure?
    I’m intrigued with your site and will check into your lessons…
    Thank you!!!

    1. That’s quite a salty solution. My guess is that it’s probably the reason you have a bit of glycerin sheen but I wouldn’t worry about it too much. See what the bars look like after the curing time and try making it again using a weaker solution.

      Saponification is mainly finished after 48 hours. I feel comfortable handling fresh soap after this time. As for your own cure time, you can measure it accurately by taking the weight of one of your bars when you unmould it. You’ll know how much water is in it from your recipe. Then work out the ratio of your other soaping ingredients to the water — you could end up with a percentage of around 20% moisture in the bar. Weight and take measurements every four days or so and when it hits about 9% moisture then it’s ready for use.

  21. Mickie Perini says:

    Thank you for sharing your recipe. Can’t wait to try it. How long do you chill in fridge if you pour into loaf mold? Thanks

  22. Mickie Perini says:

    Thanks for sharing your recipe. This will be my first time making this. If I pour into a loaf mold, how long does it need to stay in the fridge? Thanks

  23. I love making 100% CO brine soap but also want to have a go at Castille which I’ve not done before in any form. I see you mentioned that the brine would help it (olive oil soap) harden and unmold quicker but does it have a detrimental affect on the finished lather? Love your blog, thanks so much for the gorgeous inspiration x

    1. I’ve not noticed any inhibition of lather when using salt in soap. If you were worried about the amount you’re using, make a couple of test batches to see. You could also add a touch of sugar or honey to your recipe to help boost lather.

  24. Lana Sajaja says:

    Oh I have another question please? the closest sea to me is the dead sea, but it’s extremely salty I don’t think it’s usable in soap making, so could you please tell me how to prepare the brine! Is it like pickling brine?

      1. Lana Sajaja says:

        Hi again, I finally tried this soap recipe :) I absolutely love it, my husband stopped using any other soap :) thank you so much for sharing it.

  25. Lana Sajaja says:

    Hi, can I use extra virgin Olive oil instead of Pomace Olive oil. Here in Jordan we only have one kind of Olive oil (extra virgin). Thank you

    1. Of course! The colour of your bars might not be as white since EVOO tends to be darker and greener. If you don’t have an issue with that then crack on.

  26. Oh I need to try this again, I have been adding salt to the soap batter, but I think its nicer as a brine, better texture.

    1. Yep, adding salt to the soap batter does add exfoliation. It can also cause the soap to weep a bit — I’ve seen this happen with one of my batches. Dissolving it first helps if you don’t want either :)

  27. Can this type of soap be made by hot process?

    1. I think cold process is better for this soap recipe. I made this recipe with hot process and it hardens very quickly, to the point where it’s not pourable or even spoonable, it broke into chunks after it cooked for 30 minutes. I added more water and tried to mix it again and it did become more workable, but nothing like the lovely smoothness of the cold process bar pictured here in the recipe. Still a really nice and creamy bar of soap, but I would stick with cold process for the best results!

      1. Great to know! Thanks for sharing your experience with making the recipe hot-process Jennifer