Heat olive oil, grapeseed oil, and coconut oil in a double boiler until it reaches 115°F.
While the oils heat, mix together the sodium hydroxide and water in a well-ventilated area. Let it sit in an ice bath until it also reaches 115°F.
Add the oil mixture to a mixing bowl, followed by the lye water. Use an immersion blender to mix until you reach a light trace.
Add the essential oils and sage powder, and mix again until well combined.
Add spirulina powder to the outer edge of the bowl. Mix in place, then use a chopstick to swirl twice through the mixture. Pour soap into the mould.
Let the soap sit undisturbed, somewhere warm, for 48 hours. After which, you can remove the soap from the mould and let it cure for six weeks before use.
Notes
Makes 36 oz total or approximately 7 x 5 oz bars. Will fill a 2 lb soap mould.