Using a digital scale, measure out your water and pour it into a heat-resistant glass or container.

Measure out the lye and add it to the water. Stir the lye until it dissolves. Note, the chemical reaction will cause it to heat up rapidly. Set aside.

Add olive oil and sodium lactate to a large mixing bowl.

When the lye water has cooled to 120-130°F, add a little bit of it at a time to the oil in the mixing bowl.

Place the immersion blender in the middle of the bowl at the base. Pulse for several seconds, then give it a quick swirl with the blender switched off. Repeat until it comes to a thin trace.

If using essential oils, add those in now, stir well.

To mix multiple colors, separate the soap into the mixing containers. Then, add the coloring, 1 tsp at a time, until you get your desired color.

Start at opposite corners of the mold, slowly pour the soap into the mold until it spreads about 1/4 of the way across. Then at the same corner, pour the next set of colors until it pushes the soap another 1/4 of the way across. Repeat until the mold is filled.

Allow the soap to harden and sit in the molds for at least 48 hours or up to 3 days.

Remove the soap from the molds and allow it to cure for 3 months before using.