The 25er-Rezept: Germany's four-oil beginner soap, with or without palm

Ask in a German soap shop, course or book what to make first, and the answer is often the 25er-Rezept, the “25 recipe”: 25 % olive oil, 25 % rapeseed oil, 25 % coconut oil and 25 % palm oil. Petra Neumann’s Seife sieden makes it the basic recipe of the book and calls it “a real beginner’s recipe”. This guide sets out what each oil does in it, the superfat German sources use and the one we use, the lye and water from our calculator, which rapeseed oil to enter, and how to make it without palm.

What the 25er is

The name is the recipe: four oils at 25 % each, so a kilogram of oils is 250 g of each and a half-kilo batch 125 g of each. Half of it is solid fat (coconut and palm) and half liquid oil (olive and rapeseed), and German makers credit that split for its good behaviour. The Austrian soapmaker Barbara Freyberger calls the result “not too soft and not too firm”, with a batter that neither stays runny for long nor sets too fast. Neumann recommends it because it can be worked over a wide range of temperatures, which leaves a beginner time to learn the steps.

Each oil is there for its fatty acids, which the fatty acids guide explains in full:

Fatty-acid ranges from the Codex standards, as on each oil’s page.

Equal parts work because none of the four goes past the share makers usually give it. Faiola keeps palm oil to 25 % of the oils and canola to 35 %, and says some people find coconut oil drying above 25 %. The four together land inside all seven of the usual quality bands, as the table further down shows.

Buying the fats

Neumann notes that most of the basic soap fats come from the supermarket, the 25er’s four among them: coconut fat, palm fat sold as a frying fat, olive oil and rapeseed oil. Two of those need a closer look.

Palmin is coconut fat. Despite the name, it is 100 % coconut fat, made from the flesh of the coconut (Palmin), and it goes in the coconut quarter. Palmin soft is a different product: it also contains palm oil and sunflower oil (Palmin), which is why German makers say to use Palmin but not Palmin soft (Kreativseifen). Put Palmin in palm’s place and you have a different soap, half coconut oil, and the 25er’s 136.7 g of sodium hydroxide leaves 13.9 % of the oils unsaponified instead of 8 %.

A frying-fat bar is usually a blend. The bars sold as vegetable frying fat (Fettstange) are usually palm oil blended with other fats (Kreativseifen); Biskin Reines Pflanzenfett, for one, is made from palm and coconut fat (Biskin). The calculator can only use the fats you enter, and coconut oil takes about 29 % more lye per gram than palm oil. Entered as palm oil, a blend with coconut fat in it gets less lye than it can use and ends up with more superfat than you set; one with a liquid oil in it gets a little more lye than it needs. Palm oil sold as palm oil takes the guesswork out.

The superfat

The superfat, Überfettung in German, is the share of the oils left unsaponified on purpose: the lye you weigh is a few percent short of what the oils could use (see the superfat guide). German sources agree on the oils and differ on this:

The calculator’s How well is this pinned down? panel shows what each choice buys. It takes the published saponification range of every oil and works out what the lye you weighed amounts to if your oils sit at either end:

From the calculator. Taking every oil at the same end of its range at once is a bound, not a likely case. Palm oil’s range, 190 to 209 mg KOH/g, is the widest of the four.

Why we use 8 %

At 5 % the 25er is sound on paper. Even if all four oils saponify at the bottom of their ranges, 1.5 % of the oil stays unsaponified. That is a thin margin for a first batch: a scale that reads to the gram can be a gram out, and a gram is 1.4 % of the 70.6 g of sodium hydroxide a 500 g batch needs at 5 %.

At 8 % the worst case keeps 4.6 %, close to the 5 % the default promises on paper, with room left for the scale. The palm-free version further down keeps at least 5.2 % at the same setting. And 8 % is still inside the 3 to 8 % that Faiola gives as the common range. It is the figure in the LandFrauen handout, too, and our lye agrees with theirs: 68.3 g of sodium hydroxide for 125 g of each oil, against their 68.24 g.

10 % makes good soap as well, a little softer, with more free oil. We stop short of it because of the rapeseed oil. The oil a superfat leaves behind is not a fair sample of the recipe: in Kevin Dunn’s tests the leftover fat held 22 % oleic acid where the blend held 7 %, and 17 to 19 % linoleic where the blend held 9 %, which he put down to unsaturated oils reacting with lye more slowly. In the 25er the unsaturated oils are the olive and the rapeseed oil, and rapeseed carries linolenic acid, the quickest of the soap acids to go rancid. In Dunn’s orange spot tests a 10 % lye discount did not bring the orange on any sooner, but it did make it deeper.

The recipe

8 % superfat and a 33 % lye solution, from the calculator. The full batch weighs 1414.1 g before any scent, the half batch 707.1 g.

German recipes measure the water as about a third of the weight of the oils: 168 g for 500 g in the LandFrauen handout and in Neumann’s first soaps. With this lye that is a 29 % solution, against the 33 % our calculator starts at. Both work; the difference is how much water the bars have to lose as they cure, which the water guide sets out.

What the numbers say about the bar

From the calculator; the superfat does not change them. The bands are a convention hobby calculators share, not a measurement.

Every figure sits inside its band. Set beside the classic three-oil bar of 40 % olive, 30 % coconut and 30 % palm oil, our everyday bar, the 25er is softer (38 against 45 for hardness), cleanses a little less (17 against 21) and conditions more (59 against 51). Its iodine value is higher, 65 against 52: that is the rapeseed oil’s double bonds, which make a milder, softer soap and one that keeps less well.

Which rapeseed oil

Rapeseed oil comes in two kinds with different lye figures, and the calculator lists them apart. For rapeseed oil bought as food, choose canola oil (on our German pages, Rapsöl).

Rapeseed can carry over 50 % erucic acid in its fatty acids, and breeding has brought it below 2 % (BfR). Erucic acid was bred out of rapeseed in 1974, and in 1986 and 1987 double-low (00) varieties, low in glucosinolates as well, took over; apart from a few erucic varieties, only 00 rapeseed is grown today (UFOP). The 00 varieties grown for food usually hold less than 0.5 % erucic acid, and official German checks of 984 rapeseed oils found 0.26 % on average (BfR). EU law allows at most 20 g of erucic acid per kilogram, 2 %, in vegetable oils and fats sold as food, rapeseed oil among them (Regulation (EU) 2023/915). The same kind of rapeseed is sold as canola in Canada, where the name was coined: to earn it, the oil must hold less than 2 % erucic acid (Canola Council of Canada).

That is the oil our canola oil describes, from the Codex standard for low-erucic rapeseed oil: 182 to 193 mg KOH/g. The calculator’s rapeseed oil is the high-erucic kind, with more than 2 % and up to 60 % erucic acid, at 168 to 181 mg KOH/g; varieties like it are now grown only for the chemical industry, not for food (KErn). Erucic acid is a 22-carbon chain, longer than the 18-carbon acids that make up most of the food oil, so a gram of high-erucic oil holds fewer molecules and takes less lye (see the SAP values guide).

Sodium hydroxide at an 8 % superfat, from the calculator.

Gram for gram, the food oil takes 7.4 % more lye. In the 25er, where rapeseed is a quarter of the oils, the gap is 2.2 g, and the easy mistake, picking rapeseed oil by its name, runs the safe way: supermarket oil entered as the high-erucic kind gets 134.5 g, which turns the 8 % into 9.4 %. The other way round, a high-erucic oil entered as canola would end up at 6.5 %.

Linolenic acid, and keeping the bars

Rapeseed oil is 5 to 14 % linolenic acid, the fatty acid with three double bonds and the quickest of the common soap acids to oxidise (see the orange spots guide). In a comparison of cold-pressed low-erucic rapeseed oils with virgin olive oils, the rapeseed oils oxidised more easily, in part because of their higher share of polyunsaturated fatty acids (Koski et al., 2002). In the 25er, the rapeseed oil brings the recipe to 11.8 % linoleic and 2.6 % linolenic acid: 14.4 % together, just under the 15 % that Classic Bells gives as a rule of thumb, while saying the rule has no strong scientific basis. Olive oil’s linoleic acid varies from 3.5 to 21 %, so a real batch can land either side of the line.

That is a reason for care, not alarm. What helps is what the orange spots guide sets out for any soap with polyunsaturated oil in it: fresh oil, distilled water, plastic or stainless steel tools, and bars cured and stored cool, dark and airy, never on bare metal. If you like, add tetrasodium EDTA to the water and rosemary extract to the fresh oils, 0.1 % of the oils each, the doses Kevin Dunn tested; the antioxidants and chelators guide explains both.

Refined, cold-pressed or high-oleic

Refined oils are mostly colourless or pale yellow, and cold-pressed oils often an intense yellow or green (Verbraucherzentrale). Refined or cold-pressed, rapeseed oil sold as food is low-erucic and takes the same lye. Cold-pressed oil keeps for less time: about nine to twelve months in a closed bottle and two months once opened, against up to two years and six to eight months for refined oil (Verbraucherzentrale). Buy either in amounts you will use soon.

High-oleic rapeseed oil comes from HOLL varieties, with more than 75 % oleic and less than 5 % linolenic acid (LELF Brandenburg), and is sold for long high-temperature use in the food industry, catering and fast food (UFOP). If you can get it, the calculator lists it as high-oleic canola oil. In the 25er it brings linoleic and linolenic acid together down from 14.4 % to 10.7 %, for 137.2 g of sodium hydroxide at 8 %. Faiola prefers high-oleic canola for the same reason: it goes rancid less quickly.

Without palm

Palm oil is the one fat in the 25er that many German recipes now offer a way around, and the reason is land. The UN Food and Agriculture Organization’s remote-sensing survey found that the expansion of oil palm caused 7 % of all deforestation worldwide between 2000 and 2018, and on Borneo at least half of all deforestation between 2005 and 2015 was related to oil palm (IUCN). The same IUCN brief warns that simply switching to other oil crops is no solution, because oil palm yields up to nine times more oil per unit of land than the other major oil crops. Germany’s agriculture ministry takes the same view: at about 3.5 to 4 tonnes of oil per hectare, oil palm is the highest-yielding oil crop, and replacing its oil with coconut or soya would only shift the problems, or could make them worse (BMLEH).

Certification is the other route. The Roundtable on Sustainable Palm Oil (RSPO) certifies palm oil through four supply chain models: Identity Preserved and Segregated oil is certified oil kept separate from ordinary palm oil, Mass Balance oil is mixed with ordinary oil along the chain, and credits pay certified growers without the oil itself reaching you. In Germany, the Forum Nachhaltiges Palmöl brings industry, associations, NGOs and two federal ministries together on the question; in 2019, the year of the most recent study the ministry cites, just under 60 % of the palm oil used in Germany outside the energy sector was certified (BMLEH). The IUCN found certified palm oil only marginally better than uncertified oil at preventing deforestation so far. Some makers buy certified palm oil and others leave it out; the rest of this section is for the second group, and the palm-free guide goes further into what palm does and what replaces it.

Here are the fats German sources put in palm’s place, worked through in the 25er itself:

1000 g of oils at an 8 % superfat, from the calculator. Rapeseed oil stays at 25 % in every row, and olive and coconut oil at 25 % unless the row says otherwise.

Every hard fat puts the bar back within a few points of the 25er’s hardness, and each needs its own lye. Olive oil alone in palm’s place is the exception.

The swap we recommend: shea and cocoa butter

A lab worksheet from the University of Bremen gives exactly this recipe: 25 % each of olive, rapeseed and coconut oil, with 15 % shea butter and 10 % cocoa butter in palm’s place. Freyberger uses the same two butters at 10 % each with a little more coconut oil. On the numbers it is as close to the original as any: hardness 39 against 38, creamy lather 22 against 21, with less linoleic and linolenic acid. It keeps cocoa butter below the 15 % above which Faiola finds it can make a bar crack, and it keeps shea butter, the fat with the widest lye figure, to 15 %.

What changes is where the hardness comes from. Palm brings palmitic acid; the two butters replace much of it with stearic acid, whose soap is the hardest and slowest to dissolve of the common soap acids (see the fatty acids guide). Shea also carries 2.4 to 11.6 % unsaponifiable matter, which stays in the bar as it is (Akihisa et al., 2010).

Unrefined shea is the one fat here whose lye figure varies widely. The Codex standard for unrefined shea butter allows saponification values from 160 to 195 mg KOH/g, because it covers butters with up to 19 % unsaponifiable matter; butters that have been measured fall between 179.3 and 190, and the calculator uses 183. At 15 % shea and an 8 % superfat that hardly matters: even a butter at 160 would leave 6.4 % of the oils unsaponified.

The other swaps

Shea butter alone at 25 % barely moves the figures (hardness 37) and means one butter to buy. Utopia recommends shea in palm’s place but at 10 to 15 %, with the olive oil raised to make up the rest; at 15 % shea and 35 % olive oil the bar scores 34 for hardness, softer than the 25er.

Cocoa butter alone at 25 % makes the hardest bar in the table and the creamiest lather, but it is well above the 15 % at which Faiola finds it can crack a bar. Kasper gives palm’s share to two-thirds cocoa butter and one-third olive oil, which puts cocoa butter at 16.7 % and scores 37.

Lard (Schweineschmalz) takes palm’s place in one of Neumann’s palm-free first soaps. In the 25er it makes a bar a touch softer than palm, 36 for hardness, for 136.3 g of sodium hydroxide. It is not vegan.

More coconut with both butters, Freyberger’s version, gives a quicker, bigger lather: cleansing 20 at a hardness of 40. The coconut oil is then 30 % of the recipe, past the 25 % at which Faiola says some people find it drying.

Olive oil alone in palm’s place makes the softest bar in the table: hardness 30, creamy lather 13, below its band, and an iodine value of 73, above its band. Kasper finds such soaps milder, with less lather, and says they do best with about two weeks’ more cure.

Margarine turns up in German recipes too. Kasper allows a one-for-one swap only with the lye recalculated, and prefers blends for larger amounts, because margarine carries water and varies from brand to brand. Our calculator has no margarine entry: a fat whose make-up changes with the brand has no single lye figure to give it.

Whatever you choose, recalculate. Put shea and cocoa butter in palm’s place and keep the 25er’s 136.7 g of sodium hydroxide, and the 8 % superfat falls to 6.6 %.

Making it

The method is the ordinary cold process one. The first soap guide takes you through it step by step, and handling lye safely comes before it. A few points belong to the 25er:

• Two of the four fats are solid. Melt the coconut and palm oil gently, then stir in the olive and rapeseed oil, which cools the mix. Palm oil separates in its tub as it stands, so melt and stir the whole tub before you weigh any (Faiola).
• Combine between about 32 and 43 °C. The oils and the lye solution should both be in that window when they meet (Watson); they need not match. The 25er is forgiving here, which is why Neumann starts beginners on it.
• Blend to light trace, as the first soap guide describes; the trace guide shows what to look for.
• Unmould and cut after a day or two, once the loaf is firm.
• Cure the bars on edge with air all round, out of the sun, and turn them now and then. German sources most often give four to six weeks (Seifenmagie; Neumann; University of Bremen), some three to eight (LandFrauen) or four to eight (Kreativseifen). The curing guide shows how to tell when the bars are done by weighing one.

Keep the cured bars cool and dark and use the oldest first: the rapeseed oil is the part of this soap that ages first.