Only by mastering the complete set of ancient craftsmanship for the Xuanhe Single-Shuttle Imperial Silk exclusively used for Song Dynasty paintings can we establish authoritative criteria for authenticating Song artworks in the future. Scientific testing has verified that Emperor Huizong of Song’s original hand-painted works including Cranes above the Hall Roof (Ruihe Tu) and Auspicious Dragon Rock (Xianglongshi Tu) were executed on the top-tier inner-palace single-shuttle imperial silk produced during the Xuanhe reign. Its thread density far outperformed the silk used for proxy paintings by Imperial Painting Academy artists. Some scholars erroneously argue that all Song paintings were painted on double-thread silk, and single-thread silk only appeared in the Ming and Qing dynasties.
Core Term Definitions
- Xuanhe Specially manufactured by the imperial workshops under the Imperial Arts and Crafts Institute of the palace during the Xuanhe reign of Emperor Huizong (1119–1125) of the Northern Song Dynasty.
- Single-Shuttle (Dusuō) Woven in full single-thread plain weave. Both warp and weft threads consist of untwisted individual mulberry silk filaments interlaced via the back-and-forth movement of one single shuttle. It differs markedly from the double-warp combined silk widely adopted by the Imperial Painting Academy.
- Imperial Silk (Yu Juan) Restricted exclusively for Emperor Huizong’s personal brushwork, elite painters of the Hanlin Academy Imperial Painting Institute, and the remounting and conservation of ancient palace scrolls. Circulation among common people was strictly banned, representing the pinnacle of silk-making techniques for calligraphy and painting in the Song Dynasty.
Stage 1: Raw Material Selection and Silk Reeling (The First Critical Barrier, Unlimited Royal Budget)
1. Cocoon Grading
Only premium double cocoons spun by first-spring univoltine silkworms from the Taihu Lake watershed in the Jiangnan region were selected. A double cocoon is formed by two silkworms inside one casing, yielding the longest, toughest and most uniformly thick silk filaments. Defective cocoons, thin cocoons, yellow-stained cocoons, and summer bivoltine cocoons were all discarded.
2. Constant-Temperature Traditional Silk Reeling (Exclusive Palace Artisan Technique)
Cocoons were simmered in large cauldrons with thermostatically controlled warm water to dissolve the outer sericin precisely. Experienced craftsmen judged water temperature purely by tactile sensation; overheating would break silk filaments, while insufficient heat led to incomplete degumming.
Silk was manually extracted using a foot-powered reeling wheel: 40 to 50 cocoon filaments were aligned parallel to form a single raw silk strand with zero twisting. Untwisted threads remained flat and smooth, ensuring a paper-flat surface after weaving.
Top-grade early-spring silk was allocated for warp threads, and secondary early-spring silk for weft threads. This graded separation laid the foundation for ultra-high fabric density in subsequent processes.
Stage 2: Warping and Thread Drawing (Determines Silk Surface Flatness)
Thousands of single raw silk strands were combed and stretched straight, with broken filaments and uneven irregular threads removed.
Threads were evenly mounted onto warp beams to form an extra-wide breadth of over five chi, as recorded in Wen Zhenheng’s Treatise on Redundant Matters: “Song single-shuttle silk stretched more than five chi wide.” Tension across all warp threads was kept perfectly consistent throughout.
Threads were arranged in precise segmented zones with pre-calculated weaving shrinkage allowances, guaranteeing the finished silk had a straight, uniform width free of wavy slack.
Stage 3: Single-Shuttle Plain Weaving (Core Procedure Behind the Name “Single-Shuttle”)
1. Loom Structure
Heavy-duty wooden plain looms from the Song Dynasty were deployed, with a single shuttle moving back and forth to insert weft threads, hence the name “Single-Shuttle”.
- Weave structure: Simple 1-over-1-under plain weave
- Warp: All single filaments without doubling (double-thread silk adopts paired warps and single wefts)
- Weft: Equally untwisted flat single raw silk
2. Strict Density Control (Top Specification for Emperor Huizong’s Private Use)
Imperial Xuanhe single-shuttle silk achieved a warp density of ≥50 threads per centimeter and a weft density of ≥48 threads per centimeter. Under a microscope, silk filaments were arranged compactly and evenly, resulting in a texture as fine as thin rice paper, matching the original record in Treatise on Redundant Matters: “Song single-shuttle silk stretched more than five chi wide, woven to the fineness of paper.”
By comparison, standard double-thread silk from the Song Imperial Painting Academy only reached 38 to 44 threads per centimeter, with one tier lower density and inferior pigment load-bearing capacity.
3. Grey Fabric Inspection
Every bolt of woven raw silk underwent full inspection: fabrics with float threads, loose gaps, skewed wefts or thread joints were scrapped in their entirety. Zero defects were tolerated for royal supplies.
Stage 4: Ancient Degumming and Refining of Raw Silk (Defines Silk Flexibility and Natural Hue)
Freshly woven raw silk contained massive sericin, rendering it stiff, water-permeable and unable to hold mineral pigments, so full refining was mandatory:
- Degumming with rice straw ash lye: Burnt rice straw ash was mixed with water to boil the grey silk, breaking down stubborn outer sericin on silk fibers.
- Softening and conditioning with aged pork pancreas: The silk was coated with preserved pork pancreas, soaked overnight, then rinsed in warm water to eliminate residual gum. The silk became lustrous and soft with a natural ivory off-white tone.
- Shaded tension air-drying: The silk was hung taut in a cool shaded area to air-dry naturally; direct sunlight was prohibited to prevent fiber degradation.
- Full-surface polishing with clam shells: Highly polished large freshwater clam shells were rubbed repeatedly across the silk face to compress fibers and increase density, producing a jade-smooth surface. This was the core ancient Song technique known as “beaten refined silk”.
Stage 5: Confidential Palace Glue-Alum Sizing (Core Lost Technology Enabling Multi-Layer Glazing in Song Paintings)
The fully refined silk substrate received multiple coats of glue-alum solution to become water-resistant painting silk capable of dozens of stacked color glazing layers. The Xuanhe Palace formula was a closely guarded royal secret.
1. Ingredient Ratio (Imperial Formula)
- Animal hide glue: Pure glue slow-simmered from premium donkey or cow hides, featuring flexible adhesion without brittling the silk
- Alum: Purified natural potassium alum with impurities removed
- Solvent: Soft mountain spring water
2. Layered Brushing Procedure (3 to 5 total coats, fully air-dried before the next application)
- First coat: Dilute glue primer to seal micro-pores in silk fibers
- Second coat: Glue-alum mixture with a higher proportion of glue for initial waterproof setting
- Coats 3 to 5: Repeated brushing with progressively diluted concentrations. After each coat, the silk was stretched taut on wooden frames and dried slowly away from light.
Final Performance: Water beaded on the silk surface without penetration. Brushes glided with optimal frictional resistance. Mineral pigments such as azurite blue, malachite green and cinnabar red could be applied in dozens of overlapping layers without bleeding, seeping through the base or flaking off.
3. Final Compression and Polishing
Once all glue-alum coatings cured completely, the entire bolt was pressed with bluestone ingots to further compact the fabric grain. Brush lines gained powerful structural strength, perfectly fitting the full vocabulary of Song Academy painting: outline drawing, texture rubbing and heavy mineral color layered glazing.
Stage 6: Grading, Warehousing and Strict Administration
- Cutting: Fabric was trimmed by specification for large landscape handscrolls, small album leaves and square fan panels. Unbroken full five-chi-wide panels facilitated monumental creations such as A Thousand Li of Rivers and Mountains.
- Marking and tracking: Secret palace stamps and serial numbers were impressed on each bolt before storage in the Xuanhe Palace Calligraphy and Painting Repository, issued on official request to Hanlin Academy painters.
- All leftover scraps were centrally sealed and archived, never released to civilian markets.
II. Comparison: Xuanhe Single-Shuttle Imperial Silk vs. Song Academy Double-Thread Silk
表格
| Item | Xuanhe Single-Shuttle Imperial Silk (Exclusive for Emperor Huizong) | Standard Song Academy Double-Thread Silk (General Use for Academy Painters) |
|---|---|---|
| Weave Structure | Full single warp + single weft, pure single-shuttle plain weave | Paired double warps grouped together, single weft threads |
| Warp & Weft Density | ≥50 threads/cm, ultra-fine texture like paper | 38–44 threads/cm, thick and rigid |
| Thickness & Hand Feel | Lightweight, tough, uniform light transmission | Heavier, stiff and rigid |
| Glue-Alum Treatment | 5 rounds of confidential multi-layer palace sizing | 2–3 rounds of simplified glue-alum treatment |
| End Users | Emperor Huizong’s original works, top-tier imperial court paintings | Full-time Academy painters including Wang Ximeng, Zhang Zeduan |
III. Why the Craft Was Permanently Lost, and the Material Barrier Preventing Chen Danqing from Painting Song-Style Works
1. Total Breakage of Hereditary Craft Lineage
The Xuanhe Palace Imperial Arts and Crafts Institute was a dedicated royal workshop. The complete techniques for silk reeling, silk refining, glue-alum formulation and clam-shell polishing were passed down solely through master-apprentice verbal instruction and hands-on demonstration. Following the Jingkang Incident and the fall of the Northern Song Dynasty, the workshop disbanded, artisans scattered, and core formulas and operational procedures were lost forever. Modern replicas can only imitate the outward appearance, unable to restore the original fiber compactness, ink absorption and pigment retention properties.
2. Complete Disconnection in Material Systems
Oil painting canvas, industrially woven modern Chinese painting silk, industrial synthetic alum and chemical glue possess vastly different physical properties from hand-refined ancient mulberry silk. Every brushstroke, layered wash and color stacking method of Song paintings was tailor-made for imperial-grade Xuanhe silk. A mismatched painting substrate directly undermines the fundamental essence of brush momentum and artistic vitality.
3. Embodiment of the Song Dynasty’s Rigorous Spirit of In-Depth Observation
From cocoon selection and precise water temperature control to hand weaving and repeated alum coating, entire bolts of silk were discarded for flaws in any single procedure. This reverence for materials with unlimited time and cost investment formed an integral part of the spiritual core of Song painting, a closed creative system nearly impossible to replicate within contemporary artistic frameworks.
Supplementary Evidence from Ancient Texts
- Cao Zhao (Ming Dynasty), Essential Guide to Antique Appraisal: “Silk made for the Song Imperial Painting Academy was even, clean, thick and dense. Single-shuttle silk also existed, woven as fine and compact as paper.”
- Wen Zhenheng (Ming Dynasty), Treatise on Redundant Matters: “Song single-shuttle silk spanned more than five chi in width, as fine and dense as paper.”
Key Glossary for Academic Reference
- Xuanhe Single-Shuttle Imperial Silk 宣和独梭御绢
- Plain weave 平纹织造
- Sericin degumming 丝胶脱胶
- Glue-alum sizing 胶矾熟制
- Multi-layer mineral glazing 矿物颜料多层罩染
- Jingkang Incident 靖康之变
- Hanlin Academy Imperial Painting Institute 翰林图画院
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