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.
Soleseife is simply the German name for salt water soap. 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 (called a salt bar or salt soap) but soap that’s made with brine – salt dissolved in water. There are two main ways to make it yourself: 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. Many cold process soap recipes can be converted into a soleseife recipe just by replacing the water with saltwater.
This soleseife soap recipe will walk you through how to make a small batch of pure white seawater soap. However, feel free to use salt water or brine in most 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.
Benefits of Soleseife Soap
There are a few reasons that you’d use brine in soap recipe 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. The addition of 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).
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 if you’d left the salt out.
Another reason to add salt to soap is for skin therapy. Sea salt can be beneficial for the skin and is said to balance oil production and control bacteria. Both reasons make it a great addition to soap and skincare products for acne. It’s great for any skin type though.
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 make sure that 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 a 25% salinity.
Customizing this Soleseife Soap Recipe
Practically any cold process soap recipe can be converted into a soleseife soap by just replacing the distilled water with sea water 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.
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 with peppermint, lemongrass, and lavender. I have a guide to how to work out how much essential oil to use in soap recipes here.
Soleseife Soap Recipe: Natural Seawater Soap
- Stainless steel pan
- A bowl for measuring the liquid oils into
- 62 g Sodium hydroxide 2.19 oz
- 125 g Seawater / Brine 4.41 oz
- 1.5 tsp Peppermint essential oil optional
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!
Curing Soleseife Soap
Salt can help speed up the curing process by drying the soaps out quicker. However, I recommend that you still cure the soap for at least full four weeks though. 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 fluffy lather. This recipe is also high in olive oil and the longer you give it to cure, the better the soap will be.
You can use your handmade soleseife soap immediately after the curing time is up. Take a bar of soap in your hand, lather it up, and enjoy its gentle cleansing power! The shelf-life is completely dependent on the closest expiration date of the materials you used to make it with. If the olive oil you used has an expiration date of next month then that’s your soap’s best by date. Use it quick! 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. For full instructions on how to cure handmade soap head over here.
More Soap Ideas and Recipes for you
- 100% Coconut oil soap recipe
- Eco-friendly soap recipe (with video)
- Complete Guide to Natural Soap Additives
- Lovely Greens Soapmaking Ebook