It is not only the buildup of silver in the fixer that is of concern but also halide ions such as chloride, bromide and iodide. Iodide is a particular problem since it causes the fixing bath to exhaust more rapidly. Tmax and delta type films contain more iodide than do conventional emulsions. In the past when papers contained heavy metals like cadmium their builup was also a problem. Carryover of developer by insufficient time in the stop bath can also lead to staining in prints. Most photographers view fixing as a simple and straight forward process which it is not.