Initial and de-intercalated (by washing with water from formamide molecules) kaolinite was investigated by X-ray and IR spectroscopic methods. As a result of de-intercalation by water washing, changes in structural characteristics and in some physical-chemical properties of kaolinites take place: (1) the content of low-defect phase (%ldp) evaluated by the expert system of Plançon & Zacharie (1990) decreases; (2) the degree of order of the structure as determined by the Hinckley index decreases; (3) the size of coherent scattering regions (CSR) determined by the method of fourth moments decrease; (4) the rate of repeated introduction of the formamide molecules to the interlayer increases. The cause of these changes are water molecules introduced into the kaolinite interlayer as a result of de-intercalation. These water molecules have IR absorption bands at 3646 (v
as), 3550 (v
s) and 1650 (v
α) cm-1. The results obtained are discussed in relation to modern ideas on disorder models of kaolinite crystals.