Wednesday, May 23, 2012

A new mono-bath

The first time I tried a mono-bath, I added some sodium hydroxide to a salt fixer, which caused some precipitation of salt. I know trough a friend this is very normal, it is a classic experience in Chemistry to show that the ion concentration of Na in solution keeps almost constant. For that some salt is rebuilded.

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.

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