The dispersion of samples of Ca-saturated soil clay, calcium illite and calcium bentonite, was compared with the dispersion of Na clays. Each clay was first freed of electrolytes, one sample of each being dialysed with water and a 2nd washed with ethanol. All samples were then dried at 150.degree. C. The dialyzed Ca clays did not disperse in water even after a week, but dispersed spontaneously when immersed in water immediately after they had been remolded. The Ca clays that had been washed in ethanol dispersed spontaneously in water to the same extent as dialyzed sodium clays. After the samples were equilibrated at a fixed relative humidity, the water uptake in ethanol-washed Ca clays was twice that of corresponding dialyzed Ca clays but similar to the dialyzed Na clays. A mechanism of H bonding in dry Ca clay is proposed which includes exchangeable Ca, water molecules, and the exposed O of the clay layers. The replacement of water molecules in the bond by ethanol weakens the bond and leads to swelling and dispersion of the clay.