Generally, there are two types of mechanical thermometers: one is aluminum based, the other is white based ( a layer of white paint is painted on the aluminum based panel).From the buyer's point of view, the function of the panel is to display the temperature, so there is no big difference between the selection of white base and aluminum base, mainly depending on personal preference.
From the perspective of the manufacturer of the mechanical thermometer, it is different. There is a process problem here. Generally, when the temperature range is lower than 250C, the aluminum bottom and the white bottom can be selected. But when the temperature is higher than 250C, the paint on the white bottom panel may melt, so the aluminum bottom is the best choice.