The two types of bentonite clay commonly offered for detox purposes are Calcium Bentonite and Sodium Bentonite.  It can be confusing to the consumer who is trying to make a decision on the best clay to use for their personal detox regime.
 
This article will explain the different properties 
of these bentonite clays focusing on the attributes that are important 
in effective detoxification.
 
Swelling
Sodium bentonite has a natural swelling ability and will maintain its swelling ability throughout its use.  Calcium bentonite is a non-swelling bentonite. It will not 
swell without additives or chemicals. Calcium bentonite enhanced with 
additives will quickly lose its swell i.e. its swelling is short lived.
 
Cation Exchange Capacity (CEC)
Bentonite clay has a negative charge.  The
 negative charge is compensated for by adsorbing a cation on either the 
interior or exterior of the molecule (a cation is a positively charged 
ion such as many of the environmental toxins in the body including heavy
 metal ions)
 
These compensating cations, which are adsorbed on 
the particle surfaces, may be exchanged for other cations. Hence they 
are called exchangeable cations of the clay.
 
The amount of compensating cations per unit weight 
of the clay is the Cation Exchange Capacity (CEC) measured in 
millequivalents (Meq) per 100 grams of dry clay.  The higher the CEC of the clay the stronger the negative charge.
 
Sodium bentonite has a high CEC whereas calcium bentonite has very low CEC in comparison.
 
Common Uses
High purity sodium bentonite for personal use is 
selectively mined, consists of micronized particles and is supplied as a
 free-flowing powder.  It is 
commonly used as a suspending agent, viscosifier, binder and emulsion 
stabilizer for cosmetics, Pharmaceuticals and personal care products.
 
Good quality sodium bentonite for health and beauty use is specially processed to control both purity and performance.  It should meet all requirements set forth by the USPXXIII/NFXVIII for Bentonite (See USP section below)
 
Calcium bentonite is a useful adsorbent of ions in 
solution as well as fats and oils, being a main active ingredient of 
fuller's earth, probably one of the earliest industrial cleaning agents
 
 
United States Pharmacopeia (USP)
The United States Pharmacopeia (USP) is a 
non–governmental, official public standards–setting authority for 
prescription and over–the–counter medicines and other healthcare 
products manufactured or sold in the United States. USP also sets widely
 recognized standards for food ingredients and dietary supplements. USP 
sets standards for the quality, purity, strength, and consistency of 
these products–critical to the public health. USP's standards are 
recognized and used in more than 130 countries around the globe. These 
standards have helped to ensure public health throughout the world for 
close to 200 years.
 
Conclusion
Good detox clay must have some basic qualities for it to be effective: -
 
1.     The clay should have a large surface area when added to water
2.     The clay should have a high CEC value to allow it to generate a high negative charge when added to water.
3.     The clay should be pharmaceutical grade made specifically for the health and beauty industry.
 
The superior swelling ability of sodium bentonite 
gives it a much larger surface area then calcium bentonite when added to
 water (as a colloid).  Sodium bentonite also has a higher CEC rating.  These
 properties make it better for detox use since it is the high CEC that 
generates the charge necessary to attract the positively charged toxins 
from the body and the large surface area allows the sodium bentonite 
clay to adsorb far greater numbers of these positively charged toxin 
ions.
 
It’s important for the consumer to buy the best clay for the job.  In
 addition to finding sodium bentonite rather than calcium bentonite the 
consumer should endeavour to source clay that has been specifically made
 to be used in the health and beauty industry.  The clay should be USP certified so that the high safety standards for personal use are maintained.  The clay should be easily dispersed in water and should be easy to clean up without the use of chemicals.