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.