Parallel efforts to produce coloured photographic images affected the popularity of hand-colouring. In 1842 Daniel Davis Jr. patented a method for colouring daguerreotypes through electroplating, and his work was refined by Warren Thompson the following year. The results of the work of Davis and Thompson were only partially successful in creating colour photographs and the electroplating method was soon abandoned. In 1850 Levi L. Hill announced his invention of a process of daguerreotyping in natural colours in his "Treatise on Daguerreotype". Sales of conventional uncoloured and hand-coloured daguerreotypes fell in anticipation of this new technology. Hill delayed publication of the details of his process for several years, however, and his claims soon came to be considered fraudulent. When he finally did publish his treatise in 1856, the process – whether bona fide or not – was certainly impractical and dangerous.