Photoetching effects during the chemical dissolution of mercuric iodide in an iodide solution may produce noticeable surface roughening while the mean etch rate, to a first approximation, is not modified. As this phenomenon is directly related to the formation during etching of a surface chemical complex that absorbs Light, the presence or not of light is an important factor in the case of KI and NH4I etching. In contrast, the surface roughness produced after HI etching is essentially light insensitive.