Korean Hanok fenestration relies on sliding and folding timber screens (Changho) clad in handmade mulberry bast paper (Changhoji / Hanji). Crafted from the boiled, beaten inner bark of Paper Mulberry (Broussonetia papyrifera) and bound with sticky hibiscus mucilage (Dak-pul), Changhoji functions as a living environmental membrane. Mounted to intricate geometric red pine lattices (Salchang) using cooked wheat-starch paste (Nori), the paper filters harsh solar UV, diffuses soft daylight, and breathes moisture in and out, absorbing up to 500 ml of water vapor per room during humid summer monsoons and releasing it during dry winter months.
At a Glance: Key Takeaways
- Lattice Geometries: Wolsal (vertical ribs), Yongjasal (cross-lattice), Asasal (swastika fret)
- Mounting Adhesive: Pure fermented wheat-starch paste (Milgaru Nori)
- Paper Substrate: Handmade Mulberry Bast Fiber (Bakkal Hanji / Changhoji)
- Screen Lattice Timber: Straight-grained Korean Red Pine or Basswood
The Chemistry of Hanji: Paper Mulberry Bast and Dak-pul Mucilage
Unlike Western wood-pulp papers made by grinding tree trunks into short, acidic fibers, Korean Hanji is crafted exclusively from the long bast fibers found between the outer bark and wood core of the Paper Mulberry tree (Broussonetia papyrifera, known in Korean as Dak-namu). Harvested after the first autumn frosts, the stems are steamed, stripped, and boiled in wood-ash lye.
The long, unsevered bast fibers (averaging 10 to 15 mm in length) are hand-beaten on oak logs with wooden mallets. In the vat, the fibers are suspended in water along with Dak-pul—a viscous natural mucilage extracted from the roots of the Sunset Hibiscus (Abelmoschus manihot). The mucilage prevents long fibers from tangling, allowing the artisan to scoop sheets using the two-way multi-directional web technique (Eot-tteugi), which gives Changhoji extraordinary multi-axial tensile strength.
Environmental Physics: Vapor Breathability and Daylight Diffusion
A sealed glass window traps indoor humidity and causes condensation, while an open window loses thermal energy. Changhoji acts as an intelligent semi-permeable membrane. The microscopic spaces between the interwoven mulberry fibers are small enough to block direct wind and dust, yet large enough to allow individual water vapor molecules to pass freely.
During humid monsoon rainstorms, the cellulose fibers absorb excess atmospheric moisture without feeling damp to the touch. In freezing Siberian winter dry spells, the paper releases this stored moisture back into the room, maintaining stable indoor humidity. Furthermore, the multi-faceted mulberry fibers refract incoming sunlight in thousands of random directions, bathing the Hanok interior in a warm, glare-free luminescent glow.
Latticework Typologies: Wolsal, Yongjasal, and Gwiseal
The wooden framework that supports the paper is the Salchang (lattice window). Carved from fine-grained red pine or linden wood, the lattice ribs (Sal) are joined using microscopic halved-lap and mitered joints without glue or nails. Regional and social traditions dictated specific geometric patterns:
- Wolsal (Vertical Rib Lattice): Closely spaced vertical timber strips that emphasize height, traditionally used for living room exterior screens.
- Yongjasal (Chinese Character 'Yong' Lattice): An alternating cross-grid pattern that maximizes open surface area and daylight transmission, favored for scholars' study rooms (Sarangbang).
- Asasal / Manjasal (Geometric Fretwork): Complex interlocking swastika or thunder fret motifs symbolizing long life, cosmic balance, and prosperity.
Mounting Protocol: Fermented Wheat Starch and Seasonal Renewal
Mounting Changhoji is a ritual performed annually before the onset of winter. The wooden lattice is thoroughly scrubbed with water to remove old paper and adhesive. The new paper is mounted using Milgaru Nori—a pure paste made from boiled, clarified wheat starch.
The artisan brushes paste exclusively along the thin front faces of the wooden lattice bars. The dry paper sheet is rolled onto the frame, aligned with the grain running vertically, and smoothed with palm pressure. The paper is then lightly misted with clean rainwater from a fine atomizer. As the paper dries, the cellulose fibers contract by 2% to 3%, tensioning the sheet as tight and smooth as a drumhead. When tapped with a fingertip, a properly mounted Hanok screen produces a crisp, musical ringing tone.
Korean Hanji Screen vs. Japanese Washi vs. Modern Glass Comparison
Use this reference table to calculate exact physical dimensions, ratios, and specifications before purchasing:
| Performance Parameter | Korean Changhoji (Hanji) | Japanese Shoji Paper (Washi) | Modern 4mm Float Glass |
|---|---|---|---|
| Fiber Sourcing | Paper Mulberry (Dak) inner bast only | Kozo, Gampi, and Mitsumata blend | Silica melt (Non-fibrous inorganic) |
| Sheet Formation Method | Eot-tteugi (Two-way multi-directional) | Nagashizuki (One-way wave motion) | Continuous molten tin float process |
| Tensile Tear Resistance | Extremely high (multi-directional interlocking) | High along grain; moderate across grain | Zero (Brittle catastrophic fracture) |
| Moisture Permeability | High active hygroscopic buffering | Moderate vapor permeability | Zero (Impermeable; forms surface condensation) |
| Daylight Quality | Soft isotropic diffusion (Zero glare) | Translucent directional glow | Direct specular transmission (Harsh glare) |
Practical Constraints
Every successful decoration project must account for physical and environmental constraints:
Puncture Vulnerability from Domestic Pets and Small Children
Tautly stretched paper screens can be accidentally punctured by fingers, pet claws, or sharp household objects. Solution: Mount a double-layer lower kick-panel (Bunhapchang) with an un-papered solid pine bottom panel, and insert decorative pressed autumn leaves between dual Hanji layers.
Yellowing and Fiber Degradation from Intense Exterior UV Exposure
After 12 to 18 months of solar exposure, natural lignin traces in the paper oxidize, turning screens brittle and dull yellow. Solution: Adhere strictly to the traditional cycle of annual pre-winter paper renewal, utilizing 100% lye-bleached sun-cured white Hanji.
Execution Blueprint & Craftsmanship Sequence
Execute this professional sequence to achieve flawless results without backtracking:
Old Paper Removal and Lattice Cleaning
Sponge the old screen with warm water to soften dried starch paste; peel off old paper; scrub pine lattice bars with a soft horsehair brush.
Pine Lattice Truing and Joint Inspection
Inspect interlocking miter joints for racking; sand high spots; allow the cleaned wooden frame to air dry in the shade for 24 hours.
Wheat Starch Paste Cooking (Milgaru Nori)
Simmer pure wheat starch in distilled water (1:6 ratio) for 20 minutes until translucent; cool; strain through silk to eliminate lumps.
Paste Application Along Lattice Ribs
Dip a narrow 10mm goat-hair brush into the starch paste; apply a thin, uniform ribbon along the face of every wooden lattice bar.
Paper Sheet Laying and Hand Smoothing
Roll the Changhoji sheet slowly from top to bottom; press gently onto pasted bars using dry flannel cloth, working from center to perimeter.
Water Misting and Shrink-Tension Drying
Trim excess paper with a razor; mist the mounted paper lightly with a fine water spray; dry in a draft-free room to achieve drum-tight tension.
Common Mistakes & Countermeasures
Avoid these costly errors that compromise aesthetics, ergonomics, and budget:
Using Chemical Wood-Glue or Synthetic PVA to Mount Hanji Screens
Drying Freshly Misted Paper Screens in Direct Sunlight or Forced Heat
Project Execution Checklist
Track your physical progress. Checkboxes persist automatically on this device:
Frequently Asked Questions
Can Hanji screens really keep a room warm during sub-zero Korean winters?
Yes. Traditional Hanok windows often utilize a double-layer system (Ijung-chang)—an exterior sliding screen paired with an interior sliding screen. The air trapped between the two papered frames creates a highly effective thermal dead-air buffer (equivalent to modern double-glazing), while the paper itself prevents convective heat drafts from pulling warmth off the Ondol floor.
What is the meaning of placing real maple leaves between the paper layers?
This traditional poetic technique is called 'Kkot-sal-chang' or 'Danpung-chang'. During the autumn papering ritual, artisans place freshly fallen red maple or yellow ginkgo leaves between two thin layers of damp Hanji. When the sun shines through the window, the silhouettes of the leaves glow translucently, bringing nature directly into the interior living space.
Why is Korean Hanji more durable than Japanese Washi or Chinese Xuan paper?
Korean Hanji utilizes a unique multi-directional vat scooping technique known as 'Eot-tteugi', where the papermaker rocks the bamboo screen both front-to-back and side-to-side. This causes the exceptionally long mulberry fibers to weave together in an interlocking, crisscross basket-like matrix, giving Hanji superior tear resistance and dimensional stability in all directions.
How do you repair a small puncture hole in a paper screen?
Rather than replacing the entire sheet, artisans traditionally punched out a small flower- or leaf-shaped patch from spare Hanji. Applying a dab of wheat-starch paste, the patch is centered over the puncture, turning a structural flaw into a charming decorative blossom (known as 'Kkot-bap').
