Armand Hippolyte Fizeau

One of the disadvantages of the Daguerreotype was that it was extremely delicate, consisting of small particles of soft silver- mercury amalgam on the plate, which could be ruined simply by touching the surface. One solution was to frame the picture behind glass. However in August 1840 Fizeau, a French physicist, published a method of toning the daguerreotype, which in addition to increasing the contrast, made the image stronger. This consisted of treating the finished image in a solution of sodium hyposulphite and gold chloride.
In 1845 Fizeau also took the first pictures of the sun, on daguerreotypes.