mmm apparently something is not working
I bought some pure ethyl alcohol and added 5 ml in a 125 ml potassium bromide solution with about 20 g of food gelatin. The bromide gelatin was stored in a light tight bottle in the fridge.
The next day I melted the gelatin and heated some silver nitrate solution (20%) to about >40°. After the gelatine melted I went in the darkroom and under safelights poured some silver nitrate in the bromide gelatin (at 1:1 ratio). I started with just 20 ml (10 ml gelatin + 10 ml silver nitrate sol.). I mixed the whole thing until became white.
I coated the papers immediately after mixing.
The sensitized papers didn't work though. When placed into developer without any exposure to light, they became dark brown colored (a "rust" tone). It goes without saying that for exposed papers happens the same. But the same happened with the bromide gelatin prepared with denaturated alcohol. So, perhaps denaturated alcohol wasn't the problem.
The recipe was the same as the emulsion that worked in the first place but didn't keep well for more than a few days. Except that now I used separate solutions for each of the two components and I have mixed them only before coating papers. Also, I didn't use tap water, but distilled water. Could be something wrong in the mixing stage? Temperatures of each solution?
I don't think the silver nitrate is bad... I used the same solution of silver nitrate for some very nice POP prints this evening and they were just fine.
I just noticed that when I poured the silver nitrate into potassium bromide some precipitate formed and was very hard to dissolve. It looked like ordinary silver bromide precipitate, but in the previous batches I didn't notice such bigger "grains" of precipitate. They partly dissolved at the end of the mixing stage.