How much fragrance oil do I put in cold process soap?
The usual answer is 3–6% of the oil weight: 5% of 1,000 g of oils is 50 g of fragrance oil, which is 1.76 oz, or 0.80 oz per pound of oils. Three percent, the bottom of that range, is this site's default and where the recipe builder starts; go higher for a fragrance that fades; six percent is heavy and, for many fragrances, past the supplier's limit. Essential oils run lower, 1–3%, both because they are more concentrated and because many have dermal limits well under a fragrance oil's.
| Load | Per 1,000 g oils | In ounces | oz per lb of oils | % of fresh batter |
|---|---|---|---|---|
| 1% of oils | 10 g | 0.35 oz | 0.16 oz/lb | 0.7% |
| 2% of oils | 20 g | 0.71 oz | 0.32 oz/lb | 1.4% |
| 3% of oils | 30 g | 1.06 oz | 0.48 oz/lb | 2.1% |
| 4% of oils | 40 g | 1.41 oz | 0.64 oz/lb | 2.7% |
| 5% of oils | 50 g | 1.76 oz | 0.80 oz/lb | 3.4% |
| 6% of oils | 60 g | 2.12 oz | 0.96 oz/lb | 4.0% |
Illustration uses fresh batter = oils + lye + water at 33% lye concentration (1,424 g) + the fragrance. 1,000 g of oils is 2.20 lb, which sets the oz-per-lb column.
IFRA maximums are written as a percentage of the finished product: the whole bar, water and lye included. Supplier usage rates vary in basis, so check which one a rate means. Soapers state loads as a percentage of the oils. On an ordinary recipe the fresh batter weighs about 1.42 times the oils. At that starting weight, 5% of oils is 3.4% of the scented batter. Cured soap weighs less, so the same fragrance dose represents a higher percentage. Use expected cured weight in the batch field and do not assume scent loss cancels water loss. The cured-weight estimate and weighing log help establish that input.
Reading the IFRA certificate
Get the current certificate for the exact fragrance mixture from its supplier. Bar and hand soap use category 9. The maximum is a ceiling, not a recommended scent dose or a complete safety assessment. IFRA explains that suppliers issue certificates for mixtures; essential-oil raw materials need their relevant conformity and constituent information. The table below turns a sheet value into the oil-percent you are used to:
| Max on the IFRA sheet (of finished soap) | Equivalent % of oils | Max grams per 1,000 g oils |
|---|---|---|
| 1% | 1.4% | 14 g |
| 2% | 2.9% | 29 g |
| 3% | 4.4% | 44 g |
| 4% | 5.9% | 59 g |
| 5% | 7.5% | 75 g |
Arithmetic examples at the fresh-batter weight above, not cured-soap allowances. Enter your expected cured batch weight to check a bar recipe; the smaller denominator lowers the permitted grams.
Essential oils in cold process soap
Essential oils differ in composition, so a common usage range is not permission to use every oil at that rate. The supplier examples recorded here are 1.6% for lemongrass and 1.7% for clove bud in The Soap Kitchen’s 51st-Amendment documents for TSK-ESS0029 and TSK-ESS0059 respectively. Check the current documentation for your oil. They are not universal limits for those names. Weigh small doses on an appropriate scale. They also behave differently in lye: citrus fades to almost nothing over cure, florals and mints hold, spices and clove can seize a batch in seconds. Customary starting points, to be checked against the supplier's IFRA sheet for the specific oil:
| Essential oil | Customary CP load (of oils) | Notes |
|---|---|---|
| Lavender | 2–3% | Sticks well; the reliable one. |
| Sweet orange, lemon, lime (cold-pressed) | 2–3% | Fades badly in CP; 5- or 10-fold orange holds better. |
| Peppermint, spearmint | 1.5–2.5% | Strong; soapers report a cooling feel above that. |
| Tea tree, eucalyptus, rosemary | 1.5–2.5% | Medicinal notes carry at modest loads. |
| Lemongrass, litsea (may chang) | 1–2% | Potent; citral is a sensitizer, so check the IFRA sheet. |
| Patchouli, cedarwood, vetiver | 2–3% | Base notes; anchor citrus blends. |
| Cinnamon leaf, clove bud | ≤ 0.5% | Strong sensitizers; accelerate trace hard. Use as a trace note, not a load. |
Community norms for cold process, not limits; your supplier’s current conformity and constituent information for the specific oil takes precedence.
Cold process batter reaches 150–180 °F (65–80 °C) in gel and stays alkaline for days; volatile top notes evaporate and some molecules are changed by the lye. Citrus essential oils and light fragrance oils lose the most. Loading heavier is the blunt fix and runs into the IFRA ceiling; the better fixes are anchoring citrus with a base note, choosing fragrances the supplier tested in CP, and adding the scent at thin trace rather than into the hot oils.
What if I mix two fragrances or essential oils?
This checks one entered maximum. It does not add up restricted constituents shared by several scent materials. Use documentation for the complete blend; separate oils each being below a standalone limit does not establish blend conformity. The blend calculator divides a chosen total into weights, while the UK/EU labeling guide covers the separate allergen-label question.
Ounces per pound, and the 1 oz PPO habit
US suppliers often say “use 1 oz per pound of oils” (PPO). One ounce per pound is 6.25% of oils, about as heavy as it is sensible to go with most fragrance oils and above the limit for some. 0.5 oz PPO is 3.13%, a comfortable everyday load. The tool accepts oz per pound directly and shows the percent, so you can compare a supplier's PPO advice with the IFRA sheet instead of guessing.