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What is Kaolin Clay?

Kaolin Clay is chemically know as aluminum silicate. For decades, glossy paper, the type used in magazines, was made using white clay called kaolin (named after the Chinese region Kao-Ling where it was mined to produce porcelain). Paper companies are now starting to switch over to calcium carbonate (chalk). Kaolin clay is also one of the most commonly used fillers or thickening agents in paint. In the US Kaolin is white clay (found primarily in Georgia and Alabama) that contains elevated levels of the uranium and thorium decay series. This clay is believed to be derived from the weathering of granites which are known to contain elevated levels of these radionuclides.

Below is a description of Kaolin from the "Boston Museum of Fine Arts". Please take particular note of the "Synonyms" for kaolin. Some less reputable companies will try to disguise their use of kaolin as one of their ingredients by listing one of the synonyms in a attempt to confuse the questioning customer.

Kaolin - A group of hydrated aluminum silicate clays. Kaolin's are primary clays formed by the weathering of aluminum silicates such as feldspars and nephelite. When pure, kaolin is a soft, white, absorbent powder. Impurities may give it a yellow, red, blue, gray or brownish color. It occurs at many locations around the world (France, England, Germany, China, United States, etc.). Kaolin is used as a base for lake colors and as a filler in paints, cements and epoxies. Kaolin (brick dust) has been used as an abrasive.
Synonyms: kaolinite; China clay; bolus alba; porcelain clay; white bole; argilla; paper clay; brick dust; fuller's earth; white bolus; pipe clay; pipeclay
Museum of Fine Arts, Boston (2000)

For a fuller definition go to

An experiment was done in 1999 by Oak Ridge Associated Universities regarding measuring the radioactivity of magazines. You can read the results here

I found it interesting they could actually get radioactive readings off magazines. Kaolin was also the primary ingredient in Kaopectate but apparently they changed the formula some 20 years ago from what I could dig up. I wonder why! Supposedly you can still get store brand products of a similar nature that still contain Koalin. There is also another phenomenon called Geophagia. Which is defined as "the practice of eating earthly substances such as clay". Apparently it can be quite additive as seen in the article at

Some companies even go so far as to box and sell it but label it "Not for Human Consumption" knowing full well this is the purpose for which it is being purchased. A study from lists the dangers of Kaolin in their article copied below.

Effects of geophagia (kaolin ingestion) on the maternal blood and embryonic development in the pregnant rat.
Patterson EC, Staszak DJ.
Geophagia, in the form of clay-eating, is often observed during pregnancy in the human population. The intent of this study was to determine the effects of kaolin (clay) ingestion on the maternal blood and embryonic development of the pregnant rat. Thirty-six Sprague-dawley female rats were divided into three groups: control diet, 20% kaolin diet, and iron-supplemented 20% kaolin diet. The diets were fed 37 to 68 days, 69 to 95 days, and 96 to 117 days prior to fertilization, and the same diets were fed for the duration of the gestation period. The rats fed the kaolin diet exhibited significant reductions in hemoglobin, hematocrit, and red blood cell levels, thus indicating maternal anemia. There was also a significant reduction in the birth weight of the pups born to kaolin fed rats. The kaolin fed rats receiving an iron supplement maintained hematocrit, hemoglobin, red blood cell levels, and pup weight within the normal range.

The point of it all is Kaolin may not be much of a problem when it is sealed into a paint film such as latex or acrylic, except for the radioactive nature of it. The problem arises when you breathe and ingest the dust. Other powder paints on the market are made with Kaolin Clay as part of their ingredients. I don’t know how you feel but my body is assaulted every day by pollution, radiation and stress. The last thing I want to do is work with a powdered paint that is labeled "Organic" and "Environmentally Safe" that puffs dust when I mix it, leaves a dusty residue that I can ingest when sanding, all the while polluting my shop with potentially radioactive material that may also be attacking my aging body. So read the ingredients of other paints and ask questions. You can be assured that Real Milk Paint® does not, never has, and never will contain Kaolin Clay.

All the Best
Dwayne Siever