Yoroi literally means armor.
Yoroi wall describes a wall section with a zigzag finish as seen below.
Day 1 Layout and Base Coat
The following photos describe the process of creating a Yoroi wall with earthen plaster.
Beginning with a flat earthen plastered wall, layout the levels. Traditionally, an earthen plastered Yoroi wall has three equally sized sections with a flat, smaller fourth section at the bottom.
Red ink and two scribes set to 9mm and 21mm.
12mm difference between the bottom and top of adjacent sections. Red lines outline finish.
Set guides roughly 6mm above the horizontal ink line, and 10mm deep from the finish.
Plaster above the guides creating a ledge
Remove the guide, place it on the lip of the ledge, and plaster below the guide. When working with earth, one always plasters above guides first.
Plaster below guide.
Process is repeated on lower sections.
Day 2 Corner Mix
The corner mix consists of Juraku soil and hidashi shredded straw fibers. Juraku clay is renown for its strength, water resistance and lack of shrinkage.
Very stiff mix of proportionately more fiber than clay. When dry, the strongest of earthen plasters.
After wetting the ledge, a thin coat of the corner mix is driven into the wet plaster.
The guide is set at the finish height.
Nail support the guide from below.
The corner mix is applied above the guide with a 120mm trowel, but does not cover the guide.
As always, earthen plasters are applied above the guide first.
The guide is cleaned, removed, and placed on the lip of the ledge. One then applies the corner mix below the guide.
Day 3 The "Go-Around"
The Chiri, or go-around, is applied with a Chiri trowel.
The go-around mix consists of sand and Juraku soil. There is proportionately more sand than clay. The sand reduces shrinkage. Juraku soil is rather water resistant and does not dissolve easily when re-wet.
The boarders are wet with a paint brush and the go-around mix applied in multiple passes depending on thickness.
In this case, because of the final thickness, the go-around is applied in two passes.
Second pass is even with the finish.
Day 4 Finish
Water is applied to the entire section, and a thin coat of the earthen plaster is driven into the central area between the go-around.
Another thin coat is applied, just below the finish height.
Moving on to the finish coat, first the boarders are plastered.
The markings pictured here describe the process.
At the boarders, this coat is less than 1mm.
After the boarders have been plastered, the central area is plastered.
And the process is repeated with very thin layers.
Top section is finished.
Any excess at the ledge is cut off.
Top sections are dry
Texture of a brown coat finish.
Day 5 Finish
The process of Day 4 is repeated. First water is applied to the entire surface.
After plastering the central area, a smaller Jigane trowel, roughly 135mm, is used to plaster the boarders.
Boarders are complete on the second section.
Then a 225mm Jigane trowel is used to plaster the central area.
On September 8 participated in Polished Tosa Shikkui workshop at the Kyoto Plastering Institute.
Tosa Shikkui is a traditional lime and straw fiber plaster from Kochi
In order to produce the cream "Noro" that is used for polishing, Tosa
Shikkui is mixed with water and then strained through a sieve, after
which color pigments can be added.
Tosa Shikkui filtered cream "Noro"
Red pigment mixed with Tosh Shikkui Noro. Mixing the cream and pigment in a bag is clean and convenient.
Apply first coat of Tosa Shikkui over an earth plaster brown coat. Depending on the area to be polished and the need to reduce suction, the brown coat can be dampened. Apply second coat of Tosa Shikkui. Compress. Any variations in the surface of the Tosa Shikkui will be reflected in the finish coat.
When the Tosa Shikkui has stiffened up, the finish coat of cream Noro is applied. Even with a Jigane trowel, horizontal and then vertical. Remove excess cream Noro. When the variations have been corrected, compress with polished Jigane. The Jigane must be polished or it will scratch the surface. When there is too much friction to compress with the Jigane, begin compression with a polished honyaki trowel. The trowel should be polished with 1000-2000 grit water resistant sand paper. When there is too much friction to compress with the polished honyaki trowel, apply Unmo (mica group of aluminosilicates) or Tonoko (powdered stone local to Kyoto), which functions like baby powder, bringing moisture to the surface. Rubbing with your hand or soft cloth, cover the surface evenly. Before continuing, remove any access with a soft cloth. Continue compression with the polished Honyaki Finishing Trowel. And when there is too much fiction for the finishing trowel, continue compression with a polishing trowel.
Day one polished Tosa Shikkui
A detailed description of Tosa Shikkui can be found at the the Japanese Plastering Page
My sincere thanks to the teachers at the Kyoto Plastering Institute.