Strangely enough, the story of Japanese trowels and exquisite plastering begins with tea and fire.
Tea and the Japanese aesthetic

Between
the 9th and 13th centuries, Buddhist monks brought tea seeds from China
to Japan and in the 16th century, Zen practitioner Sen no Rikyu,
established the tea ceremony. The tea ceremony generally takes place in
a chashitsu, or tea house. Following the Japanese aesthetic of
"wabi-sabi", the unostentatious walls of the chashitu are plastered with
earth. As the tea ceremony and the construction of tea houses spread
throughout Japan, the art of Japanese earthen plastering flourished.
Unlimited time and resources were granted to craftsmen to create
unpretentious, but exquisite earthen plastered walls. In this way, tea
and the Japanese aesthetic led to the high development of fine earthen
plastering in Japan.
Fire, fear and awe

Like many traditional societies, in Japan, fire was something to be
feared and awed. Since most traditional Japanese buildings consist of a
wooden structure, the danger of fire was ever present. In order to
safeguard valuables and food rations, thick earthen plastered
storehouses, known as kura or dozo, were built. The massive earthen
walls of these buildings protect valuables from fire and food stuffs
from rodents and temperature extremes. However, Japan also experiences
high precipitation. In order to protect the earthen walls from
weathering, storehouses were often finished with a thin coat of Japanese
lime plaster . In a sense, the fear and awe of fire led to the
development of massive earthen plastered walls in Japan, and high
precipitation led to the development of fine Japanese lime plastering.
Through
tea and fire, we see two streams of natural plastering in Japan, fine
finishes to be appreciated and functional massive earthen walls for
protection.

Concomitant
with the spread of natural plastering in Japan, trowels were developed
for various purposes. With over 100 different types of trowels, Japan
probably hosts the largest variety of trowels on the planet. But
unfortunately, with the spread of mass produced commercial building
materials and tools, the demand for hand forged trowels has decreased.
And as a result, the number of craftsmen who produce these fine tools
are dying.

I've
been asked numerous times where one can purchase fine Japanese trowels.
Yamanishi hand forged trowels are regarded as among the best in Japan.
In cooperation with Yamanishi, I'd like to provide these trowels to
passionate plasterers abroad. These tools are expensive. They are
produced by hand for a living. And once you see the quality of the work
and hold it in your hand, you'll sense the pride of the craftsman who
produced it. If cared for properly, Yamanishi's traditional Japanese
trowels will last a lifetime.