Bi2ZnB2O7 (BZBO) fibers grown by the micro-pulling down technique (mu-PD) usually present a more or less pronounced color ranging from yellow to red and a microstructure showing glassy clear parts (more concentrated in bismuth) dispersed in a darker matrix. In a previous paper, we assumed a reaction between the platinum crucible and the melt to explain both their color and microstructure. To confirm or invalidate this hypothesis, BZBO fibers were pulled under different conditions by the mu-PD or laser heated pedestal growth (LHPG) techniques. Various physical characterizations methods such as: SEM, EDS microprobe, Raman micro-spectroscopy, DTA and X-ray diffraction were performed to evaluate their crystal quality. Finally, it appears that the origin of the observed features of the fibers grown lies in the evaporation of a substantial amount of boron oxide from the melt. This leads to a shift of its composition in the ZnO-B2O3-Bi2O3 ternary system and an incongruent melting behavior. Therefore, the obtainment of colorless and transparent fibers requires very low pulling rates. (C) 2016 Elsevier B.V. All rights reserved.