You can purchase the clay from http://www.mountainroseherbs.com/clay/clay.html or go to your local health store and purchase it. But if purchasing online I would highly suggest the link I just posted.
The most basic way to make a facial clay mask is to mix some distilled water into the clay powder to form a uniformly mixed paste. Once the paste is consistent and free of lumps, apply it in small quantities to your facial skin. Let it dry for 15 minutes or so, than rinse it off with warm water. Follow this up by using a natural toning lotion to close the opened pores and prevent further loss of moisture and microbial invasion of the opened pores. Than use a natural facial skin moisturizer that complements your skin type.
You can also add two or three drops (no more) of your favourite essential oils. For example, if you use the Red clay to make your own facial clay mask for your sensitive or mature skin, you may choose to add Clary Sage, Rose, Jasmine or Geranium. Use only 2 or 3 of these oils and don’t use more than 2-3 drops of each.
If you have very sensitive and irritated skin you might choose to make your clay mask using Red clay, a handful of chopped up cucumber, a teaspoon of honey together with some lavender and calendula or chamomile oil as the ingredients. Again start with your clay powder then add water (distilled) followed by the other ingredients. You best do this in a blender and make sure your mask is a smooth paste without too many chunks. If it gets too ‘watery’ add a little more clay, conversley if the mix is too thick, add a little water.
Don't worry too much if the paste is a little watery, as the mixture settles, it will likely firm up a little - you can always add a little water when applying the mask.
Make your facial clay mask in small batches to avoid them going off or becoming contaminated. Fresh is best and that goes not just for the food we eat, but also the food we feed our skin.
Additional Ingredients for making your own clay mask
Below is a list of ingredients suitable for the major skin types:
Melissa, Orange blossom, Lavender and most other essential oils
Avocado oil, Lemon, Grapefruit and most other citrus oils.
Frankincense, Neroli, Chamomile, Aloe vera gel
Chamomile, Calendula, Lavendar oil, clary sage, etc.
Rose, Jamine, Geranium, Neroli, etc.