if you want to make grapefruit essential oil you need to take a grapefruit and your zester and take the skin off of the grapefruit you don't want to get the white pith underneath because that's bitter and the grapefruit skin has all of the oils in it you can take this and you can dry it and once it's dry very slowly in the oven over the course of the day you can take a nice dark jar because the dark color will not allow the sunlight to break down the oils and the product and stuff it in there until it's all the jars completely filled then take a carrier oil like sweet almond oil and fill it up put it in a dark place and let it sit until the oil has the fragrance of the grapefruit then you can strain the grapefruit out of it into another container you can put in a little bottle or a bigger bottle just make sure it's dark and then you have a grapefruit essential oil that you can use as really energizing bath oil put it in a little cornstarch to make a better you can put it in bath salts you can use it just in your just as a perfume and you will have an essential oil that you can use in many different products even in soap that's how you make grapefruit essential oil