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The silver processing called ''tula'', better known in jewelery as ''[[niello]]'', is one of the variants used to made [[overlay]] decorations during in the early period of fountain pens. This process was typical of European production (and in particular has been used by [[Kaweco]]).

The silver processing called ''tula'', better known in jewelery as ''[[niello]]'', is one of the variants used to made [[overlay]] decorations during in the early period of fountain pens. This process was typical of European production (and in particular has been used by [[Kaweco]]).

The ''tula'' is an alloy of silver, lead, copper and sulfur, its color is dark gray, almost black. It's characterized by a low melting point (500 °C) compared to the silver one (about 800 °C). The process involves etchings on the silver overlay, which are then filled by the molten alloy, in order to obtain a decorative contrast between the white of the silver and the dark engravings covered by the ''tula'' alloy.  

The ''tula'' is an alloy of silver, lead, copper and sulfur, its color is dark gray, almost black. It's characterized by a low melting point (500 °C) compared to the silver one (about 800 °C). The process involves etchings on the silver overlay, which are then filled by the molten alloy, in order to obtain a decorative contrast between the white of the silver and the dark engravings covered by the ''tula'' alloy.