The silicic acid ester silazanes having the forwherein R and R are selected from the group of hydrogen, alkyl and alkenyl, R is hydrogen or an aliphatic, cycloaliphatic or aromatic radical, A is a bivalent phenol radical, m has a value of from 1 to 50 and n has a value of at least 1, are prepared by reacting a precondensation wherein R, R and A are as previously defined and X is halogen, with ammo