What happens physically during an infusion
The infusion is the dramatic high point of every sauna session, and behind it lies simple physics. When water hits the hot stones of the stove, it evaporates instantly and enriches the previously very dry sauna air with moisture. The thermometer hardly changes, but the skin feels it all the more: humid air transfers heat considerably better than dry air, and at the same time your own sweat evaporates less easily and cools the body less. The perceived temperature therefore jumps up, even though the cabin does not get hotter.
The Finns have their own word for this moment: löyly, the steam that rises from the stones, and in a broader sense the entire climate of the sauna. A good löyly is soft and enveloping rather than stinging, and that is exactly the art of pouring an infusion. It consists less of secret knowledge than of three basic principles: hot stones, small amounts of water, sparing dosage of the fragrance. Everything else is practice and personal taste.
The stones themselves also play a role: sauna stones are coarse, heat-resistant chunks that store heat and release it again instantly during the infusion. If they are loosely layered in the stone basket, the water can evaporate between them instead of running through unused. Over the years, however, sauna stones weather; so check them occasionally, restack them and replace brittle ones so that the löyly stays strong.
Important to know: the infusion belongs in the classic sauna with a stove and stones. An infrared cabin works without both, so the ritual is technically not possible there. And even in the sauna, the infusion makes the session more intense; if you are new to the subject, it is best to read our guide to using a sauna properly first and treat the infusion as a second step.
The equipment: more than a bucket and ladle
You need surprisingly little for a proper infusion, but the little you need should be right. The centrepiece is the infusion bucket, traditionally made of wood with a plastic insert that protects the wood from swelling, or alternatively made entirely of stainless steel. Then comes the matching sauna ladle with a long handle, so that you keep enough distance from the hot stove when pouring. Both are available individually or as a set; what to look for in material and workmanship is shown in our overview of sauna accessories.
The third building block is the fragrance: infusion concentrates are ready-blended mixtures of essential oils intended for dilution in the infusion water. They differ considerably in scent direction and yield, from classic birch through eucalyptus and citrus to wintry spice blends. Which concentrates have proven themselves in practice we compare separately in our overview of the best sauna infusions.
Optional, but useful: a large towel or a fanning paddle for distributing the heat, an hourglass for a sense of time and a climate gauge made up of a thermometer and hygrometer, which shows you what your infusion does to the cabin climate. If you pour infusions regularly, you won't want to give up these small helpers.
The guide in six steps
Step 1: Preheat the sauna and ventilate briefly. The infusion needs really hot stones, otherwise the water does not evaporate instantly but runs hissing through the stone basket. So heat the cabin up fully and ventilate it briefly once immediately before the session, so that there is fresh, oxygen-rich air in the cabin. Whether your stove is designed for infusions is stated in the manufacturer's instructions; our sauna stove buying guide gives an overview of suitable models.
Step 2: Prepare the water. Fill the infusion bucket with fresh, clean water, about one litre for a complete infusion. Cold to lukewarm water is perfectly fine; it does not cool the stones noticeably when dosed ladle by ladle.
Step 3: Dose the concentrate sparingly. Add the infusion concentrate to the water, not the other way round, and follow the manufacturer's dosage instructions; as a rough guide, a few millilitres per litre is often enough. Stir the mixture briefly with the ladle. The most important rule of all: never put concentrate or essential oil neat onto the stones; this is a matter of safety, not of taste.
Step 4: Pour ladle by ladle. Distribute the water over the stones in two to four ladles, with short pauses in between so that each portion can evaporate completely. Pour with your arm outstretched and keep your face and hands out of the rising steam, which is hottest directly above the stove.
Step 5: Fanning. Now comes the part that makes the infusion an experience: distribute the hot, humid air in the cabin with circling movements of a towel or fan, so that the wave of heat reaches all seats. Two or three calm passes are enough; it is about even distribution, not a storm.
Step 6: Let it linger and ventilate. Sit down, enjoy the warmth and end the sauna session as usual when your body tells you to; after an infusion, the session may well be a little shorter. Repeat the ritual at most once per session, because more infusions do not mean more recovery, only more strain on the circulation. After the session, the cabin is briefly ventilated so that the moisture escapes and fresh air is available again for the next round.
Dosage and safety
There are exactly two things that can go wrong with an infusion, and both are avoidable. The first is overdosing: too much concentrate makes the steam harsh, irritates the eyes and airways, and tips the experience from soothing to unpleasant. So stick strictly to the manufacturer's instructions and, if in doubt, work your way up from a low dose. You can always add more at the next infusion, whereas an overdosed infusion ruins the whole session.
The second risk is more serious: undiluted essential oils are flammable. Poured neat onto the hot stones, they can ignite or at least burn into acrid smoke instead of evaporating cleanly. Concentrate therefore always goes into the water first, without exception. Also make sure that no infusion water gets onto the heater housing, the control unit or the lights, and store concentrate bottles outside the cabin, away from heat and children's hands.
Finally, ventilation is part of safety: before the infusion for fresh air, and after the session against residual moisture. A well-ventilated cabin dries faster, which is also good for the wood. And as with sauna bathing in general: the infusion noticeably increases the strain on your circulation. If you have a pre-existing health condition, for example cardiovascular disease or high blood pressure, or are pregnant, check with a doctor beforehand whether and how intensively you should use a sauna.
Also think of your fellow sauna-goers: announce the infusion briefly so that nobody is caught off guard by the wave of heat, and skip it if not everyone in the cabin agrees. In the family sauna, the following also applies: children sit on the lower benches, where the wave of heat is much milder, and only stay for the infusion if they visibly feel comfortable.
Scent families and occasions
The world of infusion scents sorts itself roughly into families, and with three or four varieties in the cupboard you are prepared for any mood. Citrus scents such as orange, lemongrass or grapefruit, and menthol-based directions such as mint and eucalyptus, are felt by many to be fresh and invigorating, and suit the morning or the start of a sauna day. Herbal and woody notes such as lavender, spruce or sandalwood, by contrast, are regarded as calm evening scents with which many people end their sauna day.
Then there are the classics of the Finnish tradition, above all birch, as well as seasonal blends ranging from lily of the valley in spring to cinnamon and orange in winter. An honest assessment matters to us: scents shape the atmosphere and are perceived differently as stimulating or relaxing, and they do not promise any healing effects. If you are sensitive to fragrances, start with particularly mild varieties or simply pour on plain water, because an infusion with no scent at all is also a full löyly.
When buying, it is worth looking at yield and the ingredients list: high-quality concentrates rely on pure natural essential oils and last many months thanks to sparing dosage. For getting started, a set of three small bottles makes more sense than a litre canister of a single variety, because how a scent comes across in the hot cabin often differs considerably from how it smells on the shop shelf.
Infusion etiquette in public saunas
In German thermal baths and sauna houses, the infusion is a ceremony with fixed rules. Infusions take place at announced times and exclusively by the staff, the sauna master; guests' own concentrates or spontaneous extra ladles are taboo. The fanning is also done there by the sauna master, often with an impressive towel choreography. If you want to take part, enter the cabin a few minutes before the start, because the door stays closed during the infusion so that the heat that took effort to build up does not escape.
During the ritual, the rules are: stay seated, keep quiet, follow the sauna master's instructions. If the wave of heat becomes too intense for you, you may of course leave the cabin at any time, as quietly and quickly as possible. After the infusion, everything goes as with any sauna session: cool down, rest, drink. The good news for everyone who would rather pick up the ladle themselves: in your own sauna, you alone decide on scent, dosage and drama.
Conclusion
A successful infusion needs no talent, just sequence: hot stones, a freshly ventilated cabin, sparingly dosed concentrate in the water, two to four ladles, calm fanning, then ventilation. If you follow these six steps and respect the safety rules, you get the soft, enveloping löyly out of any cabin, for which the Finns invented a word of their own. And if you grow so fond of the ritual that you want it every day: in our comparison of the best barrel saunas and in the whole sauna guide you will find the way to your own infusion stage in the garden.