Make the lye and coffee solution. Measure out the lye and coffee in separate containers using a digital scale. The coffee must be cooled to room temperatue. Carefully add the lye to the coffee and stir until it is fully dissolved. The liqiud will shoot up in temperature and give off a burned coffee smell. Set aside to cool in a safe place.
Melt the oil and butters. Measure the oils separately, then combine them in a large pot. Melt the over medium-low heat until the shea butter is fully melted. Set aside to cool.
Stick blend to trace. Once the coffee solution and oils have both cooled to about 100-115 degrees, it's time to blend. Get out your coffee grounds, soap molds and any fragrance or color you'll be adding. Pour the lye water into the pot with the oils and blend with your stick blender until you reach trace. Add fragrance and color if using, and quickly pour into the soap mold.
Cure and unmold. Allow the soap to cure in the mold for 24-48 hours, then carefully remove it. Slice into bars. Store in a well-ventilated place and let it cure more for at least 3 weeks before using.