aquatint

Oxford , in those days , was still a city of aquatint.

牛津, 那时还是一座精雕细刻的城市.

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Aquatint: It is an etching process on copper or steel by means of nitric acid.

水彩色调: 用硝酸在钢片或铜片上作腐蚀的蚀刻法.

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