Precautions: Always wear safety goggles; splashes of lye and/or saponified oil batter can cause damage to your eyes. Wear a mask (type N95 is recommended, but not essential) while mixing your lye solution; this helps to prevent inhaling fumes that are irritating to your airways. You can take this off once you have finished the lye mixing process. Always wear a long-sleeved shirt, trousers and closed shoes while making soap; this protects you against unexpected splashes that can cause skin irritation and damage. Don't forget to wear gloves. Nitrile/latex/vinyl are suitable; avoid the thin PE type.

Prepare the lye solution by carefully pouring the sodium hydroxide into the frozen coffee. (Never the other way round! This can have serious consequences for you and your surroundings). Measure the temperature and note it down. Set the lye solution aside.

When the temperature is within the ideal range of 35° C, pour the lye solution into the oil. Remember that they should be no more than 10°C apart.

Add the coffee grounds and Coffee CO2 extract. The CO2 extract or essential oil is optional. Do not expect the scent of your coffee to remain in the soap.

Tap the mould on the table to remove air bubbles.

Set your soap aside and let it cure.

This recipe yields about 620 grams of soap in total, which comes to a maximum of 10-12 soap bars, depending on the size of the cut or soap mould. Make sure you follow the correct percentage and weight of each ingredient, as a single mistake can lead to a different result. Bear in mind that each batch of soap does not always yield exactly the same weight. You will notice that it is heavier right after making it; this is because the water evaporates during the saponification process.