Guys, don’t confuse Talbot’s early work with the later development of the Calotype. As Gerald points out Talbot used salt solution to stabilise his photogenic drawings not fix them. These were made with silver nitrate solution and a weak salt solution. AgN03 + NaCl = AgCl. Talbot noticed that without any stabilisation or fixing the image would fade more quickly at the edges of his prints (where he had brushed on less salt). Therefore using his clever inverse logic he used a much stronger salt solution over the entire image. This stabilised it, but as Gerald mentions it would still fade and change colour with time.