Verdigris

<p>Verdigris  is a common name for any of a variety of somewhat toxic <a href="/facts/Copper/I8PEE8oX">copper</a> <a href="/facts/Salt_(chemistry)/lsSKwGpn">salts</a> of <a href="/facts/Acetic_acid/uyBKA2Pd">acetic acid</a>, which range in colour from green to a <a href="/facts/Blue-green/y1t6W9RY">bluish-green</a> depending on their <a href="/facts/Chemical_composition/vjo4uMQ0">chemical composition</a>.: 132  Once used as a medicine and pharmaceutical preparation,: 176  verdigris occurs naturally, creating a <a href="/facts/Patina/IVQsrSMM">patina</a> on copper, <a href="/facts/Bronze/YCYCVIKt">bronze</a>, and <a href="/facts/Brass/pe8EHk6x">brass</a>, and is the main component of a historic <a href="/facts/Green_pigment/tj1IJvbu">green pigment</a> used for artistic purposes from antiquity until the late 20th century, including in <a href="/facts/Easel/736FHpyF">easel painting</a>, <a href="/facts/Polychromatic_sculptures/v2xP9kr3">polychromatic sculptures</a>, and illumination of maps.: 414–423  However, due to its instability, its popularity declined as other green pigments became readily available.: 171  The instability of its appearance stems from its <a href="/facts/Hydration_number/R0oYIN6T">hydration level</a> and <a href="/facts/Base_(chemistry)/M9wA7qeM">basicity</a>, which change as the pigment interacts with other materials over time.: 637 
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Verdigris open-in-new

Verdigris