Soap making with pure essential oils is one of the most rewarding aspects of natural craft, but it comes with some important technical considerations that synthetic fragrance oils simply do not have. Essential oils are complex, volatile, and react differently to the high pH environment of cold process soap. This guide covers everything UK makers need to know to get consistent, professional results.
Do essential oils survive saponification?
This is the most common question from new soap makers, and the answer is: it depends on the oil. The high pH of cold process soap (typically between 9 and 10) and the heat generated by saponification can degrade or destroy more delicate essential oils - particularly light citrus oils like lemon, grapefruit and bergamot FCF. These may fade significantly or disappear entirely in finished soap.
Heavier, more robust oils - cedarwood, patchouli, vetiver, clove, cinnamon and lavender - survive saponification much better and provide good lasting scent in the finished bar. If a customer tells you a scent that tested beautifully in a candle has "disappeared" in their soap, scent fade during cure — not a faulty oil — is almost always the reason. It's worth explaining this to customers upfront so they choose a soap-appropriate blend rather than assuming something went wrong.
Usage rates for essential oils in soap
As a general guideline for cold process soap, use essential oils at 2 to 3% of the total oil weight. As a working example: for 1kg of base oils, that's roughly 20 to 30g of essential oil. For melt and pour, you can typically go slightly higher - 2 to 3% is still a safe starting point. Always check the IFRA certificate for your specific oil or blend, as some essential oils have lower maximum permitted usage levels in rinse-off products.
All our essential oil blends come with IFRA certificates that include rinse-off product categories, so you can quickly confirm safe usage rates before formulating.
The best essential oil blends for soap making
Lavender blends
Lavender is the most reliable essential oil for soap making. It survives saponification well, performs consistently across hot and cold process methods, and appeals to almost every customer. Our Wellbeing Sleep blend of lavender, bergamot and vetiver makes a beautiful spa-quality soap with excellent lasting scent.
Citrus blends
Pure citrus oils fade in cold process soap. However, when blended with fixative base notes like cedarwood, patchouli or vetiver, the overall blend retains much better. Our Lime Basil and Mandarin blend and Lemonade blend both perform well in melt and pour and reasonably well in cold process when used at the higher end of the recommended rate. Our Spa Tranquility blend (citrus and lime) is a popular choice for spa-themed soap ranges — use it at the higher end of your batch rate to offset cure fade.
Earthy and woody blends
Our Forest blend of sweet orange, ylang ylang, cedarwood and sandalwood is one of the most popular soap making blends in our range, holding up well through cure and suiting unisex or gift bars. Our Earthy Tones blend of cedarwood and grapefruit is a dependable autumn/winter bar scent.
Floral blends
Our Love Me Tender blend of lavender, neroli and ylang ylang is a soft floral that performs consistently in cold process soap.
Spa blends
Day at the Spa and Relax at the Spa both perform excellently in soap. The eucalyptus, lavender and bergamot combination survives saponification well and creates a genuinely spa-quality product.
CLP compliance for handmade soap in the UK
If you are selling handmade soap in the UK, your product is classified as a cosmetic under UK Cosmetic Regulations. This means you need a Cosmetic Product Safety Report (CPSR) from a qualified assessor before you can legally sell. You will also need a Product Information File (PIF) and correct labelling including INCI ingredient names and allergen declarations.
This is separate from CLP labelling, which covers the fragrance ingredient as a chemical substance. All our essential oil blends come with SDS sheets and IFRA certificates to support your CPSR application.
Tips for getting the best results
- Add essential oils at trace - the cooler the better - to minimise evaporation during the pour.
- Use a fragrance calculator to work out the correct weight of oil for your batch size.
- Test a small batch first, particularly with new blends, as some essential oils (clove and cinnamon especially) can accelerate trace significantly.
- Allow cold process soap to cure for a full 4 to 6 weeks before testing the scent strength - the scent develops and settles significantly during cure.
All EOB essential oil blends are available from 10ml up to 500ml so you can test a new scent in a small batch before committing to a full production run. If you're formulating a new range and want help matching a scent to your base oils and expected cure time, get in touch — we work with soap makers across the UK on exactly this.
Browse our full range of essential oils for soap making here.