Andrea Norman, age 10, of Houston, Texas, for her question:

What is fuller's earth?

Fuller's earth is an old, old servant of mankind. It is a clay or a soft rock and from earliest times it has been used in the preparation of woolen cloth. In the days when weaving was done on a hand loom, the fuller was the man. who fulled, or filled out the woven material.

When taken from the sheep' s back, wool is clammy and sticky with lanolin and other oils. Yarns made from this raw wool are tight and stringy, When this yarn is woven, the fabric is tacky and full of tiny gaps between the threads. The fuller's jab was to remove the tacky stuff from the wool, leaving only enough natural oil to make the threads soft and silky. With this material removed, the yarn fluffed out and became loose and springy. The little gaps between the threads disappeared,

All sorts of skills were used in this fulling job. The wool was. heated, steamed, moistened and pressed or milled. But along with these tricks the fuller was sure to use a special. kind of clay which came to be known as fuller's earth. This clay is merely a muddy mixture of some of the most common elements in the earth's crust.

More than 50 per cent of fuller's earth is silica, a compound of silicon rind oxygen. It also contains aluminum and water. In color, fuller's earth may be dirty white, tan, almost any shade of brown or sometimes blue, This simple mixture has a talent for purifying dark oils, fats and grease. When it comes in contact with a dirty, tacky material, it drinks up the dark organic matter, leaving the fat or oil clean. and clear. Fuller's earth usually breaks up and soaks away with running water.

The fullers of olden days used the earth in powdered form. They spread it on the greasy wool and left it to do its work. Then they soaked and rinsed the wool end the grease‑ladened earth ran away with the water. A clay with such a valuable talent is useful in modern times. In fact we use morn fuller's earth today than they did in the days of hand looming. Its main use is in the purifying of our fats and oils. It is used as a filter to take the dark organic matter from mineral oils and from vegetable fats and oils. Chances are, the can of vegetable shortening in your kitchen was filtered and purified through a layer of fuller's earth.