In the world of modern architecture, where drywall and paint often dominate, the ancient Japanese craft of Sakan (plastering) offers a textured, breathable, and deeply historical alternative. Japanese plastering is not merely a method of covering a wall; it is an art form that dates back over a millennium, evolved through tea houses and castles, and is now finding a resurgence in contemporary design.

Here is an overview of the materials, history, and techniques of Sakan, based on traditional practices.

A History Etched in Earth

The roots of Japanese plastering run deep. The oldest existing examples of Sakan work in Japan can be found at the Horyu-ji Temple (built around 607 AD) in the Golden Hall and Five-Story Pagoda. The technique involved layering earth three times and finishing it with white clay, a process remarkably similar to modern methods.

While early techniques were influenced by craftsmen from the continent, Japan developed its own unique expressions over time. By the Momoyama period, following the introduction of firearms, thick Shikkui (lime plaster) was used on castle walls for bulletproofing and fire resistance. Conversely, the famous tea master Sen no Rikyu championed the humble, rustic aesthetic of earth walls (Arakabe) for tea houses, appreciating the texture of exposed straw.

The Essential Materials

Sakan materials are generally categorized into three main binders: Clay (color earth), Lime, and Gypsum/Cement. To these, craftsmen add aggregates for texture and Susa (hemp or straw fibers) to prevent cracking and improve binding.

1. Earth (Tsuchi)

Earth walls are quintessential to the Japanese aesthetic, known for their warmth and humidity regulation.

• Juraku: Originally sourced from the site of the Jurakudai palace in Kyoto, “Juraku wall” now refers generally to fine, colored earth finishes. The highest quality, Hon-Juraku (Mizu-gone), is polished using only water, earth, and fine straw, requiring high technical skill.
• Otsu: A durable finish made by mixing earth with a small amount of slaked lime. The “Otsu Polish” is a prestigious finish where the wall is compressed and polished until it glows.

2. Lime (Shikkui)

Traditional Japanese Shikkui is distinct from Western lime plasters. It is a mixture of slaked lime, seaweed glue (boiled funori or tsunomata), and hemp fibers.

• Tosa Shikkui: Born in the typhoon-prone Kochi prefecture, this variant involves fermenting the lime and straw mixture for months to create a thick, durable, weather-resistant paste.
• Polished Shikkui (Migaki): A technique where the plaster is compressed repeatedly with a trowel until it achieves a mirror-like reflection.

3. Cement and Modern Mixes

While traditional materials are prized, modern Sakan also utilizes cement for durability and versatility.

• Washed Finish (Araidashi): Cement mixed with pebbles is applied, and before it fully cures, the surface is washed with water to expose the stones.
• Rammed Earth (Hanchiku): A technique of compacting layers of earth (often stabilized with lime or cement) into formwork to create walls that look like geological strata.

Distinctive Finishes and Textures

The beauty of Sakan lies in the “hand” of the artisan. The finish can range from glass-smooth to rugged and organic.

• Firefly Wall (Hotaru-kabe): A poetic finish where iron-rich earth is applied. Over time, the iron oxidizes, creating small dark spots that resemble fireflies.
• Scratched Finish (Kakiotoshi): Before the material hardens, it is scratched with a wire brush or tool to create a rough, stone-like texture.
• Combed Finish (Kushibiki): A trowel with comb-like teeth is dragged across the surface to create linear patterns.
• Namako Walls: A striking black-and-white design often seen on storehouses, featuring tiles with thick, semi-circular plaster joints that protect against rain and fire.

The Modern Resurgence

Today, manufacturers are bridging the gap between traditional craft and modern convenience. “Pre-mixed” materials allow for consistent quality and easier application.

• Functional Walls: Materials like Shirasu (volcanic soil) and Diatomaceous Earth (Keisodo) are popular for their ability to absorb odors and regulate humidity.
• Innovative Coatings: New technologies include flexible mortars like MORTEX that can cover existing tiles, and metal coatings like Midas Metal which contain 90% real metal for a patina finish.

Whether restoring a cultural heritage site or designing a modern luxury hotel, the art of Sakan provides a tactile connection to nature and history that industrial materials simply cannot replicate.