I measured, for the salt solution, with a new pH meter bought at ebay, about 4, but that was not correct, a salt solution has a ph varying between 6,7 to 7,3, we may assume that it is a neutral solution. The pH meter showed a different value and to make the solution basic I added sodium hydroxide. For the developer to act you need a basic pH.
After discovering this fact, I decided to give up adding sodium hydroxide and to use just salt and parodinal. This time the process run at room temperature, slightly bellow 20 ºC. The amount of parodinal was 1:100, which I use to develop in two bath developer. The development time was 18 hours, in order to get the daguerreotype effect, a silver compound which reflects more light so that when you see it against a dark background it looks positive. This is only possible from the emulsion side of the film in which the picture is inverted, like it was also in the original daguerreotypes.
I am happy with the results. The film can be used either as negative or positive inverted.
|Negative at transparency|
|Positivated in GIMP|
|Scanned reflexive in color mode with a black background|
|Scanned reflexive in B&W mode of the scanner|
500 ml salt fixer
5 ml Parodinal
18 hours development (or more) @ R.T.