Animal Glue — 아교 (Agyo)

Types of Animal Glue

막대아교 (Plate Glue)

Standard hide glue in stick/block form. Most common and widely available. Used for general sizing, as a binder for 석채 and 분채 pigments, and in 아교반수 (the sizing solution applied to paper and silk before painting). Standard concentration: 10% binding medium.

알아교 (Pearl/Bead Glue)

Hide glue in small bead/pearl form. Dissolves more easily than plate glue. Same function as 막대아교. Standard concentration: 알아교 10%.

어교 (Fish Glue)

Glue derived from fish skins, bones, and scales. Stronger adhesive quality than hide glue. Use at a lower percentage than 막대아교 due to higher viscosity. Used where stronger adhesion is needed.

민어부레아교 (Mineo Fish Bladder Glue)

The highest-quality and most expensive traditional Korean glue — derived from the swim bladder (부레) of 민어 (yellow corvina, Larimichthys crocea). Stronger adhesive than 녹교. Used in historical document restoration, fine silk painting, and bow-making (활 제작). Best processed and dried in winter. Historically used where maximum bond strength is required.

녹교 / 녹영교 (Nok-gyo — Green Glue)

A specific traditional glue used for gold work — applying 금니 (gold ink) in Buddhist manuscript painting (사경). Used in fine decorative arts where a clean, non-yellowing glue is needed for gilding and gold line work.

도교 (Dogyo — Peach Tree Resin Glue)

Glue derived from the resin of wounded peach trees. A plant-based adhesive that performs similarly to animal glue for some applications. Used in traditional woodwork and fine arts as an alternative to animal glue.

물아교 (Mul-agyo — Plant-Based Glue)

Plant-based glue — a vegetable alternative to animal glue. Lower bond strength than animal glues but fully vegan. Used in applications where animal glue's slight yellowing or protein properties are undesired.

Rabbit Skin Glue (RSG)

Western equivalent of the traditional Korean hide glue system. Made from rabbit skin — a particularly pure and consistent source of collagen. The standard sizing agent for canvas in oil painting (under gesso). RSG forms a more flexible film than generic hide glue, making it well-suited to the movement of stretched canvas. Concentration for canvas sizing: approximately 3–5% solution.

Agyo-bansu (아교반수) — Glue Sizing for Paper and Silk

Agyo-bansu (아교반수, glue sizing) is the solution applied to paper (한지) or silk before painting to control absorbency. Without it, pigments bleed uncontrollably. The solution combines 아교 with baekban (백반, alum, potassium aluminium sulfate) in a critical ratio:

Ratio: agyo (아교) 5 : baekban (백반, alum) 1

Critical instruction: Always dissolve 백반 in cold water. In hot water, 백반 becomes strongly acidic and can damage silk fibres and react unexpectedly with pigments. Grind the baekban (백반, alum) to fine powder in a mortar (약사발/막자사발) before dissolving in cold water. Then combine with the warm 아교 solution.

Sizing concentrations:

• Paper (한지): 1.5% agio solution
• Silk (비단): 2–3% agio solution

Apply with a wide brush (배접붓) in smooth, even strokes. Allow to dry fully before painting. A cup warmer helps maintain 아교 at working temperature without overheating.

Funori — Algae Binder

Funori (布海苔, Gloiopeltis furcata) is a red algae native to Japan and Korea, used as a sizing agent and binder in Japanese traditional gilding, textile sizing, and paper restoration. It produces a clear, non-yellowing size with excellent flexibility — unlike animal glue, it does not crack when dry. Used at 1–2% solution.

In silk dyeing and painting, funori can replace or supplement 아교 where a more transparent, flexible film is needed. It is also used as a paste for mounting and conservation of fragile works on paper.

Preparation of 아교 Binder

1. Soak 막대아교 or 알아교 in cold water for 30–60 minutes until softened.
2. Heat in a double boiler (never direct flame) to approximately 60°C — do not boil. Boiling destroys the collagen structure and weakens adhesion.
3. Stir gently until fully dissolved.
4. For 아교반수: add powdered 백반 (dissolved separately in cold water) to the warm 아교 at a 5:1 ratio.
5. Keep warm using a cup warmer during application — 아교 sets quickly when it cools below 40°C.

Common Failures

• Agio solution too thin: Pigments bleed through the size. Increase concentration.
• Agio too thick: Creates a stiff, brittle film that cracks. Silk becomes stiff and loses drape.
• 백반 dissolved in hot water: Creates strong acidity. Damages silk. Always use cold water for 백반.
• Agio boiled: Protein structure is destroyed. Bond strength is reduced significantly. Use double boiler, maximum 60°C.
• Pigment cracking off: Insufficient agio in pigment mixture. Mix to thicker paste consistency.

Jay's Studio Note

장미님 워크숍 revealed the full complexity of the 아교 system — from the everyday 막대아교 for routine sizing through to the specific 민어부레아교 used for the highest-quality gold work and documentary restoration. The 아교 5:백반 1 ratio, ground in mortar and dissolved always in cold water — is one of those specific technical details that separates a proper 아교반수 from a rough approximation. The 컵 워머 on the worktable is a simple but critical tool: 아교 starts to set the moment it cools, and working with cold 아교 is impossible.

References

• 장미님 워크숍, Seoul 2026
• 호림미술관 / 국립중앙박물관 (traditional Korean painting resources)