A wide porcelain or enameled dish with a small pouring spout on one end. Evaporating dishes were used in the preparation of various photographic chemicals such as silver nitrate, where crystals are formed and then washed to remove unwanted acid. On a smaller scale, wet plate photographers frequently used large evaporating dishes to remove the alcohol and ether from overworked silver nitrate solutions. These could be used at room temperature or placed on a stove to accelerate the effect. Special heated and vented evaporation dishes were used in graphic arts darkrooms, when the collodion process was used.