From Dorene Petersen <dorenep.EUROPA.COM>:
I have made quite a lot of infused oils and the following is from the Aromatherapy Certificate Correspondence Course offered by the Australasian College of Herbal Studies.
It's not that technical but hope its helpful:
How to prepare your own infused oils at home
There is nothing more satisfying than gathering a basket of fresh jasmine, honeysuckle or rose blossoms on a warm summers day and then preparing your own infused oil. There are three methods for preparing an infused herbal oil. You can use fresh or dried herbs. Flowers are best fresh, although the perfume of some flowers intensifies with drying such as gardenia, daphne and boronia. If using fresh, double the quantity as all recipes given are for dried herbs. If using fresh herbs for any of these methods leave the herbs to wilt for six hours to reduce their water content which will spoil the final product.
15 gm (1/2 oz) dried or if fresh use 30 gm (1 oz) herb (this is the total amount so if you are using a blend make sure you do not have more than this)
1 cup of oil
Measure the herbs and oil and mix the oil to the herbs in a stainless steel bowl. Heat over water bath (a saucepan 1/4 filled with water) also known as a double boiler, which should be simmering. Make sure the bowl is not sitting on the bottom of the pot but is floating in the water. Keep the lid on the oil. Stir occasionally and simmer for 30 minutes. Watch the oil does not get too hot. It should not smoke or bubble. It can burn easily and will develop an acrid smell if it overheats, which is very difficult to disguise. Strain through four layers of butter muslin or some other very fine non-metal strainer. Strain twice if necessary as it is important to get all herbs out of the oil to prevent the herbal oil from going rancid or moldy. Essential oils can be added at this stage for perfume and added therapeutic benefits.
Use the same quantities of herbs and oil as for the waterbath method or approximately 3 tablespoons of finely cut herbs to 300ml (10 oz) of oil. The quantity of herb can be increased to produce a stronger oil. Put the herbs in a jar with a tight fitting lid and pour over the oil. Make sure the herbs are completely covered with oil. Add one tablespoon of apple cider vinegar or white wine to help break down the plant material. Leave the jar to sit in the sun all day and in a warm cupboard at night for two weeks. Strain through four layers of muslin. This process can be repeated two to three times to give a stronger oil. The final product should be strong enough to leave an aroma when massaged on the skin. Always test infused oils on the skin. Don't rely on just your nose.
Use the same quantities of herbs and oil as for Waterbath method. Place the herbs and oil in a crockpot and leave on a low heat for two hours. Follow the recipe above for straining.
To preserve oils
This is only necessary if you are preparing large quantities that you intend to store.
- Add 1/4 tsp. simple tincture of Benzoin to 1 cup vegetable oil. Tincture of Benzoin is prepared from the gum of an Indonesian tree, Styrax Benzoin. Make sure it is simple tincture of Benzoin. Compound tincture of Benzoin, also known as Friars Balsam, is not suitable.
- Add 500 I.U. of natural mixed Tocopherols or Vitamin E to 1 cup of vegetable oil.
Dorene Petersen <dorenep.EUROPA.COM>