Making Herbal Bath Oils part 2: Heat Infusion

In my first post about making herbal bath oils I was learning about solar infusion, or the cold method.  This post focuses on heat infusion, also known as the hot method.  I realised heat infusion was possible because one of my early efforts was James Wong’s Orange, Clove and Myrrh Body Oil.  Here, I’m looking more generally at why and how to do this.

The question of which method to use depends on the qualities of the specific herb to be infused.  Fresh plants can rot during the time required for solar infusion (this may be what happened to my original ill-fated sunflower and calendula oil), while certain barks and roots will also give up their properties more easily using the hot method.  Getting to know what works best for each herb is probably best thought of as a trial and error period, using small quantities of sunflower oil to keep the costs to a minimum.

Once you know a method works well for your herb, you can experiment with a variety of oils to find the one you like best.  As with solar infusion, any good quality oil that is pourable at room temperature can be used.  I have used sunflower, olive and sweet almond oils.  The photo above shows my first two efforts: fragrant pink rose infused in sweet almond oil (I was hoping this would take on a little of the pink colour of the three rose blooms used, but this didn’t happen) and calendula infused in sunflower oil.  In addition, heat infusion also allows you to use butters and oils which are hard at room temperature, such as shea butter and coconut oil.  On the other hand, this method does require more hands-on attention than solar infusion.

Here’s how to do it

1. Herbs to be used should be picked first thing in the morning, after the dew has dried but before the heat of the sun has time to evaporate the essential oils from the plant.  Clean and shake them to ensure there are no insects or dirt.  If necessary wash them gently and leave to dry on kitchen paper.
2. Chop the herb finely.  Dried herbs should be crushed but not powdered.
3. Pour the oil into a heatproof bowl and add the prepared herbs.  Place the bowl over a pan of water simmering on the stove.  Use a thermometer to ensure you achieve a temperature of around 38C (100F).
4. Continue to warm the oil and to stir it for 2 to 4 hours or more.  The oil should take on the colour and scent of the herbs.
5. Remove the bowl from the pan and leave to cool.  (Butters and solid oils should not at this stage be left to cool to the extent that they solidify.)
6. Strain the oil into a clean jar.  I use a funnel with a coffee filter paper to do this.  At the time of writing I have not yet infused using solid oils – it may be that these would require muslin / cheesecloth for straining.  Leave the oil to settle.  It’s important to allow any sediment to settle to the bottom of the jar.  If you don’t do this your oil will be cloudy, or the sediment may even cause it to become mouldy over time.  You may need to leave it overnight.
7. Pour the oil into clean bottles ready for use.  I have found the best way to clean them is in the dishwasher, because the cycle also dries inside the bottles.  Boiling them in a large pan of hot water leaves moisture that takes for ever to clear.
8. Finally, label the bottle.  I include the oil and herb used and the date.  If I were giving the oil as a gift – which I haven’t done yet – I would also include a removable tag with directions for use, along with the beneficial properties of the herb.  I have found my hand-written labels don’t withstand splashes!

Although I have focused here on using herbal oils for the bath, these same oils can also be used for massage, and some can be used in cooking.

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