Device and method for chemical deposition on an elongated member (2) of vitreous material in which a rotating gripping member (5) causes a first end portion (2a) of the elongated member (2) to rotate (20). The second end portion (2b) of the elongated member (2) is borne by a pair of supporting members (34, 35) which are axially spaced apart (L1) and are capable of permitting angular rotational movement and axial sliding of the second end portion. Each supporting member (34, 35) also applies a radial constraint preventing the second end portion (2b) from moving away from the axis of rotation, thus forcing the second potion (2b) and the elongated member (2) to lie with a longitudinal axis coaxial with the axis of rotation (18). Any curvature of the elongated member (2) is corrected and recovered in this way.