Origin and technology of the Georgian brick at Fade Mansion, Dublin, built c. 1728

Abstract

This paper studies the provenance and firing technol ogy of the Fade Mansion brick. The microstructure was studied with scanning electron microscopy ( SEM ), mineral associations and transformation were determined with X-ray diffraction ( XRD ) and petrographic analyses. The results evidenced that the bricks were made with a decalcified, silica-based clay of glacio-flu vial origin, gathered locally. This agrees with the position of the Mansion on a terrace of the River Liffey, and with previous research on historic bricks made with boulder clay. They were fired in kilns in an oxidising atmosphere. The rubbers at window heads reached lower temperatures which resulted in low vitrification, leading to weathering. Initial vitrification structures generally concur with the occurrence of clay minerals, indicating temperatures of c. 800°C. Continuous vitrification is associated to the disappearance of clay minerals, the sintering of hematite and/or high-tem-perature phases and mica transformation, indicating a wide temperature range >950-1200°C, which agrees with the inconsistent brick properties. study based on the application of several analytical of The study The mineralogical composition was analysed with X-ray diffraction (XRD) using the method, with a Phillips PW1050/80 and a Micrographs electrons) and spectra at 20KV. Brick also for thin-section of 40X The high-temperature assemblages include: quartz polymorphs cristobalite and tridymite (>1000°C), cordierite, hematite, spinel and magnetite, indicating that temperatures reached c. 1000-1200°C. As seen in the introduction, previous authors have proven that, in non-carbonate sediments, hematite forms above 1000°C, while spinel appears at 1000-1100°C and magnetite in the range 1000-1250°C.