Sauna aroma for sauna rouryu. When you pour aroma water on a hot sauna stone, the aroma scent envelops the room along with water vapor. The scent of vihita (bundled birch branches and leaves) often used in Finnish saunas. The scent of Vihita in the sauna tub wafts freshly. How to use: Dilute before use. A good rule of thumb is about 5 liters of water for 0.5-1 cup of cap. Do not apply it directly to your skin or massage it with oil. You can also use the bamboo bowl as a mini room diffuser. Strictly prohibited: Do not put undiluted solution in the sauna stove as it is, as it may cause a fire.