Patina – Sabi – 寂 – is a term too extensive to be briefly described in any simple way. Therefore, this point will be more comprehensive. What exactly is patina? It is reaction of materiál surface, in our case metals, to the temperature and chemical elements contained in air, water, human sweat and the like. Each metal reacts differently with these chemical elements, such as iron, exposed to humidity and air form red iron oxide Fe2O3 (hematite).Quite the contrary, silver is resistant to water and air. Some metals, such as copper, form a protective layer of a mixture of copper carbonate and copper hydroxide to prevent further surface corrosion. But in the case of iron or steel, red iron oxide does not fulfill such a function, and unless the access of air and moisture is prevented, it continues to erode the surface until complete disintegration of the object.
Together with metal processing technology, man has addressed two important questions of how to protect the surface of metal objects from the weather and later, how to make the object more attractive. Thus, the patination / surface treatment of metals is as old as the processing of metals themselves.
We divide patinas into:
Outdoor – created by natural influences without human intervention.
Natural – the effect of climate and long-term use. For example, brass fittings of Buddhist temples handrails, where frequent contact with hands of visitors has created a beautiful brown patina on the surface.
Artificial – a reaction of chemical agents that accelerates processes needed to create a outdoor type of patina, or to create surface layers that can not be achieved either outdoor or naturally. This category also includes blacksmithing methods of surface treatments.
A combination of artificial and natural – when only the initial reaction is evoked, but other influences affect further development of the patina.
Tsuba mounted on a warrior’s sword had to withstand the both island’s climate and sweat, blood. And this could only be achieved by creating a resistant layer. Blacksmith’s surface treatment methods have survived for millennia to this day. Another and most common method that dominates the vast majority of all preserved historical tsuba is the corrosive patina Tecusabi – 鉄 錆. The color range of this patina is from reddish brown to dark black.
Like a swordsman was able to estimate metalurgical quality of a blade from quality hone, also quality of iron of a sword guard can be determined from structure and quality of patina. And the like widespread cosmetic hone can deceive eyes and supported by chemicals can raise an average sword by two levels up, it is also possible to simulate quality of tsuba to a certain extend.
Later, from the 16th century, along with the tea ceremony, the teaching of Zen Buddhism, and cultivation of warriors, a new demand for the aesthetics of things arose. People learned to see beauty in natural shapes and structures, and with their products they tried to approach these ideals, thus, the object was not made by human hands, but by nature itself.
This trend was also reflected in the production of sword guards. The products of the best masters then excelled in the exceptional quality of steel and patina, which was difficult to imitate, and the production processes became the most protected secrets of individual schools. During Edo period, various producers tried with greater or lesser success to imitate the works of big names from older periods, such as Yamakichibei or Nobuie. But nobody achieved the same results.