Herb-to-Oil Ratio
You can prepare the Calendula oil infusion using two different approaches: folk and weight-to-volume.
With the folk method, loosely pack your herbs into a jar, leaving an inch of space at the top.
Pour oil ( like sesame, grapeseed, or jojoba ) over the plants until they are completely submerged under oil. Fill oil nearly to the jar brim to reduce oxidation of the oil and molding of the plant matter.
In the weight-to-volume method, herbs and oil are typically combined in a 1:5 ratio, but I find that 1:10 allows for easier handling. To get these proportions, use ten times the amount of oil (measured by volume) for every one part of herb (measured by weight). For example: 25 grams of herbal material to 250 milliliters of oil.
Choosing an Extraction Method
Oil infusions can be prepared with or without heat. The heatless process, or maceration, is slower but doesn’t damage the delicate constituents in the plants or carrier oils. You can use heat to speed up the infusion process, reducing the extraction time from weeks to only a few hours. However, heated methods require more mindfulness to ensure the oil doesn’t get ruined. Resinous herbs like Calendula are best extracted using heat and longer processing time.
Maceration Method
Place the sealed jar in a sunny window. Cover with a paper bag in order to protect from damaging UV light. Shake daily for four to six weeks.