How to Make Seaweed-Infused Oil

Seaweed-infused oil is a wonderful base for skincare products, packed with nutrients that nourish and rejuvenate.  This guide will walk you through the entire process of making a seaweed-infused oil, from foraging seaweed to crafting your own infusion at home. 

Safe and Responsible Foraging 

Before you start, it’s important to harvest seaweed safely, responsibly, sustainably, and legally.  For detailed guidance, check out my blog post: Seaweed: Safe, Responsible, and Legal Harvesting.   

Which Seaweed? 

For this recipe, we’re using Serrated wrack (Fucus serratus), a common seaweed found in rocky coastal areas.  It’s easy to identify with its dark brown or olive-green fronds and jagged, saw-like edges.  It’s brimming with nutrients like vitamins A, B12, C, D, and E, plus minerals like iodine, potassium, and magnesium.  Its antioxidant, anti-inflammatory, and antibacterial properties make it a powerhouse for skincare.  

If you'd like to learn more about the health benefits of seaweed, here's a research paper to get you started: Phychochemical Constituents and Biological Activities of Fucus.

You can experiment with other seaweed types, and I highly recommend it, but always research their suitability for skincare and follow good harvesting practices. 

Preparing Your Seaweed 

Seaweed collected from the beach often carries sand and tiny sea creatures (bycatch).  Before taking it home: 

- Swish in seawater: Clean the seaweed thoroughly in seawater to remove debris and bycatch. 

- Rinse at home: Quickly rinse the seaweed in cold water, but don’t overdo it—freshwater can damage its cell membranes and cause it to release those wonderful enzymes that we need to retain.  

- Dry gently: Pat the seaweed with a clean towel, then dry it completely using one of these methods: 
-- Air drying: Tie with twine and hang in a warm, ventilated space. 
-- Oven drying: Place on a rack in a low-temperature, fan-assisted oven for a few hours.   

- Ensure fully dry: Moist seaweed can introduce bacteria, causing contamination in your oil infusion and any products you make with the oil.  If your infused oil turns cloudy, even when it is fully settled, this is a sign that it's contaminated.  You will need to discard the oil and start over. 

What is an Oil Infusion? 

An oil infusion, or maceration, uses carrier oil to extract the therapeutic properties of plants. The result is a nutrient-rich base for your skincare formulations. 

To extract these wonderful benefits, you will need a medium to act as a solvent.  We may commonly think of a solvent as a harsh chemical substance, but a solvent is any liquid that can be used to dissolve other substances.  In this case, our solvent is a plant oil.

Choosing the Right Oil 

Sunflower oil is a fantastic choice for this pupose: 

- Affordable, widely available, and suitable for all skin types. 
- Rich in linoleic acid to maintain the skin’s barrier and prevent moisture loss. 
- Contains vitamin E, which acts as a natural antioxidant, extending the infusion’s shelf life.

Feel free to explore other oils like olive, almond, or jojoba, depending on your needs. 

Tip: Before making your first infusion, I highly recommend keeping a dedicated notebook.  Use it to record every step you take, including the ingredients used, where you collected the seaweed, and a batch number that can be transferred to your infusions and any resulting products.  This practice is essential for safety, traceability, and troubleshooting.  It also allows you to track what worked well and identify areas for improvement, ensuring consistent results in the future.

The Solar-Infused Method 

 Preparation:

1. Sterilise equipment: Use dry, sterilised jars or bottles with tight lids to prevent contamination.
2. Measure ingredients: Start with a simple 10% seaweed to 90% oil ratio (e.g., 10g dried seaweed to 90g oil).

Steps: 

1. Grind the seaweed: Coarsely grind dried seaweed in a food processor. Avoid over-processing to a fine powder.
2. Combine in a container: Add the ground seaweed to your container, then fill with oil, leaving minimal air space. Swirl and gently tap container on a surface to release air bubbles.
3. Label and store: Label with the contents, date, and batch number (e.g., “Seaweed Oil Infusion, Batch 001, 24/01/2025”). Add a “Not for Consumption” warning label.
4. Infuse in sunlight: Place the container on the sunniest spot available for 3–6 weeks, shaking every few days.

- Take photos weekly to observe colour changes. 

- Record notes on the infusion process in your notebook.  

Straining and Storage:

- After 3–6 weeks, strain the oil using a fine tea strainer or muslin cloth into a dark glass container.  Make sure the container is completely sterile.

- Label with a 6-month use-by date,  and store in a cool, dark and dry place. 

Alternative methods for a quicker result 

If you don’t want to wait weeks for your infusion, you can speed up the process by following the above steps, but instead place your container in a slow cooker or double boiler for around 4 hours, on a very low heat.  This will work just fine, but personally I find that the solar method yields the best infusions overall.  You may want to experiment with both methods to experience the difference first-hand.

Using your infused oil 

Your nutrient-packed seaweed oil is now ready to be used in formulations like balms, creams, and serums.  In my next blog post, I’ll share a simple recipe for a seaweed lip balm.

If you have any questions or need help with any part of the process, feel free to get in touch. 

Big love, 
Jay