How do I prepare and apply a face mask with this black clay?

Measure 1–2 teaspoons of powder into a non-reactive bowl. Add water, hydrolate, herbal infusion, or yogurt gradually while stirring until you have a smooth, spreadable paste — not runny, not stiff. Apply an even layer to clean skin, avoiding the eye area. For oily or combination skin, leave on 10–15 minutes; for dry or sensitive skin, limit to 5–7 minutes. Important: do not let the mask dry completely. If it starts to feel tight or crack, spritz with water or rinse immediately to avoid dehydrating the surface. Rinse thoroughly with lukewarm water and follow with your usual moisturiser. Use 1–2 times per week. If you have reactive skin, do a patch test on the inner forearm 24 hours before the first full-face application.