Analysis of the Most Important Scientific Studies for Diagnosing Ru Yao

Introduction

Ru yao (汝缶) is one of the Five Great Wares of the Song Dynasty, known for its unique aesthetics and complex production technology. Authentic Ru ware originates from the Qingliangsi kilns (清凉寺窝址) in Baofeng, Henan. Over the past decades, research in archaeology, materials science, and physical chemistry has made it possible to identify diagnostic features of genuine Ru yao.

This article compiles and systematizes 15 key scholarly publications that form the basis for diagnostic protocols, along with two original research studies by Prof. Nona Dronova (Zenodo, 2025).

Review of Key Studies

Study #1 — Wang C. (2010)

Title: “In Search of the True Discoverer of the Ru Kiln Site”
Key Findings:

• Qingliangsi confirmed as the authentic Ru kiln site

• Tianqing glaze with bluish-gray tone

• Setter marks and minimalistic forms

Study #2 — Liu Yi (1997)

Title: Annotations to Qing Bo Za Zhi
Key Findings:

• Aesthetic descriptions of Tianqing glaze recorded during the Song Dynasty

• “Sky after rain,” “like jade”

Study #3 — Tao Zongyi, Shuo Fu

Title: Shuo Fu (Collected Writings, 14th c.)
Key Findings:

• Cultural reiteration of Tianqing color

• Describes glaze as luminous and jade-like

Study #4 — Wang Xiangqian (1985)

Title: Kuitian Waicheng
Key Findings:

• Color: translucent, misty blue

• Crackle: nearly invisible; gloss: soft

• Forgeries: overly bright, artificial tone

Study #5 — Zhao J. et al. (1989)

Title: Investigation and Trial Excavation of the Qingliangsi Ru Kiln Site
Key Findings:

• First official archaeological confirmation

• Seven kilns, triangle setter marks, light gray clay body

Study #6 — Guo M. et al. (2001)

Title: 2000 Excavation Brief of Qingliangsi Ru Kiln
Key Findings:

• 1600 artifacts, 9 kilns, three glaze development stages

• Secondary coloration of crackle observed

Study #7 — Ding Y. et al. (2017)

Title: Scientific Study of Grayish-Green Glaze from Qingliangsi Ru Kiln
Key Findings:

• Glassy glaze structure with anorthite crystals

• Fe²⁺ creates Tianqing tone in reducing atmosphere

Study #8 — Zhang M. et al. (2008)

Title: XPS Study of Iron Valence in Ancient Porcelain Glazes
Key Findings:

• Fe²⁺/Fe³⁺ ≈ 2.4 in Ru yao

• Color formed by Fe²⁺ in the glass phase

Study #9 — Li R. et al. (2002)

Title: Mechanism of Color Formation in Ru Glaze via NAA and Mössbauer Spectroscopy
Key Findings:

• Over 70% of iron present as Fe²⁺

• Fe²⁺ uniformly distributed in the amorphous glass phase

Study #10 — Chen Y. et al. (2020)

Title: Structural Influence on Color of Grayish-Blue Glazes
Key Findings:

• CIELab: L* ~63, a* –2.5, b* +1.0, h° ~165°

• Color arises from scattering in homogeneous amorphous matrix

Study #11 — Li W. et al. (2005)

Title: Phase-Separated Crystalline Glaze in Ru Ware from the Northern Song Dynasty
Key Findings:

• Microstructure: glass + anorthite

• Drop-like and reticulated phases; jade-like glow

Study #12 — Yang Y. et al. (2005)

Title: Microstructural Analysis on Ru Ceramics, Imitations, and Jun Ware
Key Findings:

• Authentic Ru: L* ≈ 63.5, h° ≈ 161°

• Imitations: more yellowish, overly glossy

Study #13 — Doherty & Ding (2016)

Title: Petrographic and Geological Characteristics of Ru Ceramics
Key Findings:

• Body: kaolinite >85%, no quartz, grain size 2–5 μm

• Color: light gray to gray-white

Study #14 — Vandiver P. (2016)

Title: Technological Comparison of Song Dynasty Green Glazes
Key Findings:

• Ru has the most glassy, light-scattering structure

• Dense body and soft reflection

Study #15 — Zhang F. et al. (2002)

Title: Ru Ware Glaze Color, Surface Texture, Fish Scale Pattern & Etch Pits
Key Findings:

• "Fish-scale" pattern under 20× magnification

• Color: h° 120–140°, low-sheen jade-like gloss

Additional Research by Prof. Nona Dronova (2025)

Study #16 — Dronova, N.D. (2025)

Title: Glaze Color and Crackle Morphology in Southern Song Ru Ware: Diagnostic Protocols
Zenodo DOI: 10.5281/zenodo.16688585

Contribution:

• Microanalysis of crackle and glaze tone

• Practical diagnostic protocols combining CIELab + morphological criteria

Study #17 — Dronova, N.D. (2025)

Title: Ru yao Glaze Identification via Hue Angle and Optical Analysis
Zenodo DOI: 10.5281/zenodo.16678677

Contribution:

• Quantitative color range for Tianqing (h° = 160–170°)

• Methodology for authenticating Ru glaze using digital tools

Conclusion

Comparison of historical, archaeological, petrographic, and physicochemical sources enables a robust methodology for diagnosing Ru yao:

• Tianqing glaze: h° ≈ 160–170°, soft inner glow

• Glass matrix + anorthite: key to optical properties

• Body: purified kaolinite, light-gray

• Triangle setter marks and tight, net-like crackle

The contributions of Prof. N.D. Dronova confirm the application of combined spectrophotometric and morphological indicators in expert authentication.

Bibliography

1. Wang C. (2010), Cultural Identification & Evaluation, No.3

2. Liu Yi (1997), Qing Bo Za Zhi Notes, Zhonghua Book Co.

3. Tao Z., Shuo Fu, Xinhua Press, 1986

4. Wang X. (1985), Kuitian Waicheng, Zhonghua Book Co.

5. Zhao J. et al. (1989), Cultural Relics, No.11

6. Guo M. et al. (2001), Cultural Relics, No.11

7. Ding Y. et al. (2017), China Cultural Relics Science Research, No.4

8. Zhang M. et al. (2008), Nuclear Technology, No.9

9. Li R. et al. (2002), Chinese Science Bulletin, Vol. 47

10. Chen Y. et al. (2020), Int. J. Ceram. Eng. Sci., Vol. 2(4)

11. Li W. et al. (2005), Ceramics International, Vol. 31

12. Yang Y. et al. (2005), Journal of Archaeological Science, Vol. 32

13. Doherty C.J., Ding Y. (2016), Science Press Beijing

14. Vandiver P. (2016), Five Great Wares Conf. Proc.

15. Zhang F. et al. (2002), Shanghai Ceramic Symposium, pp. 194–200

16. Dronova, N.D. (2025), Glaze Color and Crackle Morphology, Zenodo: 10.5281/zenodo.16688585

17. Dronova, N.D. (2025), Ru yao Glaze Identification via Hue Angle, Zenodo: 10.5281/zenodo.16678677