Scanning electron microscopy (SEM) has been used to investigate ceramic vitrification stages since the 1970s, however its application has been primarily restricted to stoneware and high-fired ceramics. The purpose of this study was to determine whether stages of vitrification could also be identified in prehistoric low-fired archaeological earthenware ceramics via SEM using northern Chilen samples covering a period c. 2000 to 500 years BP as a case study. This was achieved by visually comparing microstructural changes between original and re-fired ceramic sherds. The microstructural changes identified in this study indicate that the potters who made these vessels achieved early stages of vitrification. This result demonstrates that SEM is a useful technique to investigate the development of firing technology in earthenware manufacture.