Precautions: always wear safety glasses, as splashes of lye or soap batter can damage your eyes. When mixing the lye solution, wear a mask (N95 type is recommended) to avoid inhaling fumes, which are irritating to your respiratory tract. You can remove the mask once the lye is mixed. Always wear a shirt with long sleeves, long pants and closed shoes, and don't forget your gloves. Nitrile, latex or vinyl are suitable; do not use thin PE gloves.

Prepare the lye solution: carefully pour the sodium hydroxide into the cooled coffee. Never the other way around, as this can be dangerous. Measure the temperature, note it, and set the lye solution aside.

Is the temperature around 35 degrees? Then pour the lye solution into the oils. Make sure both are no more than 10 degrees apart.

Add the coffee grounds and the coffee CO2 extract. The CO2 extract is optional; don't expect the coffee scent to remain in the soap.

Tap the mold on the table to release air bubbles.

Set your soap aside and let it harden.

This recipe yields approximately 620 grams of soap, good for 10 to 12 soap bars, depending on how large you cut them. Follow the percentage and weight of each ingredient precisely; one mistake already produces a different result. By the way, each batch weighs slightly different: immediately after making, the soap is heavier because water still evaporates during saponification.