Academia.eduAcademia.edu

Figure 1 – uploaded by Chandra Reedy

See full PDFdownloadDownload figure
Table 1. Main methods of coal cinder ceramic production

Table 1 Main methods of coal cinder ceramic production

Related Figures (10)

Fig. 1 a. Firing and ash glazing processes of coal cinder ceramics. a. In Yingjing, multiple pots are fired in a shallow brick-lined pit. The kiln lid is levered off when the pots are orange hot, so they can be moved to an adjacent deep ash-glazing pit. © C. L. Reedy.
Fig. 1 a. Firing and ash glazing processes of coal cinder ceramics. a. In Yingjing, multiple pots are fired in a shallow brick-lined pit. The kiln lid is levered off when the pots are orange hot, so they can be moved to an adjacent deep ash-glazing pit. © C. L. Reedy.
Fig. 1 b. Firing and ash glazing processes of coal cinder ceramics. b. In Gaoxian, one pot is fired at a time in a hole in the coal pile, then moved into a shallow ash-glazing pit. © C. L. Reedy.
Fig. 1 b. Firing and ash glazing processes of coal cinder ceramics. b. In Gaoxian, one pot is fired at a time in a hole in the coal pile, then moved into a shallow ash-glazing pit. © C. L. Reedy.
Fig. 2 a-b. Examples of Yingjing coarse wares with a shiny ash glaze. a. Cooking vessels; b. Medicine pots. © C. L. Reedy.
Fig. 2 a-b. Examples of Yingjing coarse wares with a shiny ash glaze. a. Cooking vessels; b. Medicine pots. © C. L. Reedy.
Fig. 3 a-b. a. A Yingjing shop display including teapots, teacups, and art pottery; b. Hotpots, the main product of the Gaoxian workshop. © C. L. Reedy.
Fig. 3 a-b. a. A Yingjing shop display including teapots, teacups, and art pottery; b. Hotpots, the main product of the Gaoxian workshop. © C. L. Reedy.
Fig. 4 a-b. Thin sections mounted in blue epoxy (plane polarized light) of Yingjing coal cinders deemed “qualified” and similar to Type 1, with layered clay fragments and quartz in a carbonaceous matrix (a); and “unqualified” and similar to Type 2, with extensive glass filled with mullite needles within a porous carbonaceous matrix containing prills of hematite and iron sulfide and some iron spinel (b).
Fig. 4 a-b. Thin sections mounted in blue epoxy (plane polarized light) of Yingjing coal cinders deemed “qualified” and similar to Type 1, with layered clay fragments and quartz in a carbonaceous matrix (a); and “unqualified” and similar to Type 2, with extensive glass filled with mullite needles within a porous carbonaceous matrix containing prills of hematite and iron sulfide and some iron spinel (b).
Fig. 5 a-b. Thin section of a Yingjing coarse ceramic (a) showing well-developed mullite in glass from use of Type 2 coal cinders, plane polarized light; and of a Gaoxian product (b) with round reddish hematite prills and smaller and more lustrous TiO, (reflected light).
Fig. 5 a-b. Thin section of a Yingjing coarse ceramic (a) showing well-developed mullite in glass from use of Type 2 coal cinders, plane polarized light; and of a Gaoxian product (b) with round reddish hematite prills and smaller and more lustrous TiO, (reflected light).
Fig. 6. Micro-CT and image analysis views of pores in a Yingjing coarse ware with 17.07% volume porosity (closed and open). Left, 3D reconstruction of a region of interest taken from the scan of a 0.5 cm’ field of view; center, pores (blue) segmented from matrix (yellow) using a classical machine learning model (Random Forest — Activation Map 2); right, pores color-coded by aspect ratio showing a morphological difference between the surface-connected pores and the interior pores. The uneven ash glazes of Yingjing coarse products are thicker and more evenly distributed on the surface than those of Gaoxian, reflecting differences in the glaze pit designs and time during which the ceramics are kept in the pit. These “glazes” that form as the hot ceramic surface encounters the burning resinous organic material inside the hot pit. They are composed of very porous glass which incorporates fine-grained quartz, ash particles, and incip- ient anorthite. The fine grained teawares lack glaze, as they receive only the first firing (in saggars). As they are made with very finely-ground coal cinders, only small chunks of quartz, cristobalite, and glass are visible within very fine black powdered carbon. Micro-CT scans were done on six Yingjing coarse cooking pot sherds, two Yingjing fine teaware sherds, and four Gaoxian sherds (two from the original workshop and two from the relocated one). The results are summarized in Table 3. The 3D image analysis of the scans (fig. 6) shows Yingjing coarse wares have an average volume porosity (open and closed pores) of 17.23%; however, measurements vary from 13.64-22.84%, likely reflecting variations in the mineralogical composition of various batches and sources of clay and coal cinders, materials preparation, and firing temperatures from one workshop and production run to another that could lead to differences in sintering and vitri- fication behavior of the ceramic matrix. Gaoxian ceramics present a consistent porosity volume of about 17%, in spite of the workshop relocating, likely because the potter and his wife are sole operators of the production and firing
Fig. 6. Micro-CT and image analysis views of pores in a Yingjing coarse ware with 17.07% volume porosity (closed and open). Left, 3D reconstruction of a region of interest taken from the scan of a 0.5 cm’ field of view; center, pores (blue) segmented from matrix (yellow) using a classical machine learning model (Random Forest — Activation Map 2); right, pores color-coded by aspect ratio showing a morphological difference between the surface-connected pores and the interior pores. The uneven ash glazes of Yingjing coarse products are thicker and more evenly distributed on the surface than those of Gaoxian, reflecting differences in the glaze pit designs and time during which the ceramics are kept in the pit. These “glazes” that form as the hot ceramic surface encounters the burning resinous organic material inside the hot pit. They are composed of very porous glass which incorporates fine-grained quartz, ash particles, and incip- ient anorthite. The fine grained teawares lack glaze, as they receive only the first firing (in saggars). As they are made with very finely-ground coal cinders, only small chunks of quartz, cristobalite, and glass are visible within very fine black powdered carbon. Micro-CT scans were done on six Yingjing coarse cooking pot sherds, two Yingjing fine teaware sherds, and four Gaoxian sherds (two from the original workshop and two from the relocated one). The results are summarized in Table 3. The 3D image analysis of the scans (fig. 6) shows Yingjing coarse wares have an average volume porosity (open and closed pores) of 17.23%; however, measurements vary from 13.64-22.84%, likely reflecting variations in the mineralogical composition of various batches and sources of clay and coal cinders, materials preparation, and firing temperatures from one workshop and production run to another that could lead to differences in sintering and vitri- fication behavior of the ceramic matrix. Gaoxian ceramics present a consistent porosity volume of about 17%, in spite of the workshop relocating, likely because the potter and his wife are sole operators of the production and firing
Table 2. Minerals observed in raw materials versus fired ceramics
Table 2. Minerals observed in raw materials versus fired ceramics
a. Minimum orthogonal Feret diameter/maximum Feret diameter is used as a measure of pore elongation. b. Volume/surface area ratio (volume in relation to outside surface area of the pores) is an indication of sphericity since for a given volume the ratio is maximized for spheres. c. The % of pores in the system that are isolated and unconnected to any other pores. d. The maximum number of other pores to which any pore in the system is connected. Table 3. Yingjing and Gaoxian ceramic pore systems
a. Minimum orthogonal Feret diameter/maximum Feret diameter is used as a measure of pore elongation. b. Volume/surface area ratio (volume in relation to outside surface area of the pores) is an indication of sphericity since for a given volume the ratio is maximized for spheres. c. The % of pores in the system that are isolated and unconnected to any other pores. d. The maximum number of other pores to which any pore in the system is connected. Table 3. Yingjing and Gaoxian ceramic pore systems
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved