Seaweed Soap Recipe with Skin-Nourishing Sea Kelp

How to make an all-natural seaweed soap recipe from scratch using babassu oil, sea kelp, and skin-brightening essential oils. Full instructions using the cold process method and explains why seaweed is great for the skin.

I just love the smell of this soap. Lavender, rosemary, tea tree, and the slightest scent of the sea. It really clears the lungs and invigorates the mind, and I can tell that this is going to be wonderful to use this winter! Being a big fan of simple natural soapmaking, I also love the color that the dried kelp and French green clay bring to this seaweed soap recipe. A soft tan that is close to the shade of some seaweeds. Each speckle of powdered kelp is surrounded by a tiny golden halo formed as it infused into the bar during the cure time.

In this piece, I’ll introduce you to using seaweed in soap recipes and give you a simple way to add it as a beginner. You can add seaweed as instructed to practically any soap recipe, though. It imparts color, a light scent, and skin nourishment.

Using Seaweed in Soap

There are several ways to use seaweed in soap, and this recipe shows you the easiest way. Powdered seaweed can be added at trace in most cold-process soap recipes. It’s best to pre-mix it in a little oil, though, since powdered soap additives can tend to clump, leaving blobs in your bars. Dried and powdered seaweed is usually added at up to 1 tsp PPO (per pound/454 g oils).

Dried seaweed that is not a powder can be used in soap-making in at least two ways. You could also use whole, or chopped, dried seaweed as a botanical decoration for the top. I’d advise this only if you live in an area without high humidity, though.

You can also reconstitute dried seaweed in the distilled water you plan on making soap with. Warm the water up first and leave the seaweed to sit in it overnight. The next day, many of the polysaccharides in the seaweed will have infused into the water. Dip your fingers in, and you’ll notice a silky and almost gelatinous texture. You can either strain the seaweed out or puree it in the water and use it to make the lye solution. One part fresh seaweed to three parts water is a good amount. If using dried, use one part seaweed to four parts water.

You can use fresh seaweed as described above, but you can also use it (or reconstituted seaweed) to make a puree. Add the seaweed puree at trace at up to one Tablespoon per pound of soaping oils.

Foraging for Seaweed

Though this recipe calls for purchased powdered sea kelp, you can use foraged sea kelp, bladderwrack, or other skin-safe seaweed. If you do so, ensure that the seaweed you collect is from a clean beach uncontaminated by pollution, dog mess, or sewage. Collect it from below the tide line, if possible, and pick seaweed that looks healthy and plump. You don’t need much seaweed to make soap, so forage only what you need and adhere to local laws on foraging from the beach.

If you’re unsure which seaweed you can collect, refer to local foraging information and good books. One that I have is the Edible Seashore Handbook from River Cottage. Seaweeds that you can use in soapmaking include spirulina, sea kelp, bladderwrack, and nori. Some have been shown to give skin benefits, and others simply add color.

Once collected, rinse the seaweed thoroughly in cold water to remove sand and muck, and then pat dry with a kitchen towel. After that, you can either freeze, dry, or use the seaweed fresh.

Seaweed can last up to a year frozen or dried. Refrigerated, fresh seaweed only lasts a few days. If you dry the seaweed, you can store it whole or as a powder. For a powder, grind it using a food processor, ninja blender, or similar. Sift it through a sieve to get a fine powder. And if you’re wondering about nori sheets that you’d use for sushi, yes, you can use them for soapmaking too.

Why Make this Seaweed Soap Recipe

Seaweed adds some really lovely qualities to handmade soap. As a powder, it mainly adds color and scent and also light exfoliation. As a puree (added at trace) or infusion (used for the lye solution), it can also load your bars with silky polysaccharides, making them even more silky than usual. Polysaccharides make marshmallow extract such a silky and nourishing skin ingredient, and that is why I use it in skin cream. To really make use of them, you should make a water infusion of the seaweed the night before. Though I don’t go through that step in this recipe, you can add it if you wish.

Seaweed is also used in skincare to help delay the signs of aging and to promote collagen production and skin healing. Studies have shown that those using bladderwrack (Fucus vesiculosus) gel on the face noticed increased elasticity and decreased skin thickness in just over a month. I’m not saying that this soap will do anything to help, but it is an intriguing idea.

Sea kelp is another group of seaweed that you can use in soap making. There are several types, and I use Ascophyllum nodosum in this recipe. There are many species of sea kelp though, and you can use many of them (perhaps all?) in soap making. Containing incredible amounts of vitamins, minerals, and essential fatty acids, sea kelp is often used in facials and other spa treatments. Like bladderwrack, sea kelp has been attributed to increasing skin elasticity and even helping subdue the signs of aging and wrinkles.

Seaweed Soap Recipe Ingredients

You’ve heard all about the star ingredient in this seaweed soap recipe, but there are a few more I’d like to introduce you to. This soap recipe does not use coconut oil and instead uses babassu. It’s very similar to coconut in its soapmaking properties and might be more suitable for people with a coconut allergy. It also speeds up trace, so contributes to this soap firming up very quickly.

Clay also speeds up trace, so I use just a little to help even the color of this recipe. I did make a batch with double the amount of seaweed and clay and didn’t notice it tracing any quicker. Both are fast, though, so please don’t use an immersion blender. Clay is also great for oily skin, as are the essential oils in this soap recipe. I share a lot more information on different types of clays (and colors!) in my piece on how to naturally color soap with clay.

Essential Oils in this Soap Recipe

Although optional, the lavender, tea tree, and rosemary essential oils work to balance skin issues. They give this seaweed soap recipe a gorgeous scent that even masks the scent of seaweed. Not completely, but enough that it’s not overpowering.

Lavender essential oil has a beautiful floral scent that blends well with rosemary and tea tree. It also has healing and soothing properties, which is why I use it in skin salves and lavender balm. We use rosemary and tea tree essential oils in soap recipes for their anti-bacterial, anti-fungal, and stimulating properties. While rosemary is wonderful for mental fatigue, tea tree helps to heal acne and other skin complaints. The scents of both are also an excellent therapy against migraines and tension, as is lavender.

More Seaside Inspiration for You

The seaside has many treasures, both beautiful and edible, to enjoy and create with. Here are some more ideas for you to explore:

• Make Soleseife: A Seawater Soap Recipe
• How to make a Sea Glass Candle
• Foraging for Wild Food on the Beach
• Beachcombing for Sea Glass
• Make seaweed fertilizer for the garden