Negative 1  Under red lighting best quality writing paper is dipped in weak silver nitrate solution, followed by potassium iodide solution, and wiped dry. 2  One side is coated with an ‘exciting’ solution of gallic acid and silver nitrate, applied with a brush. The sensitised paper is then dried  in  front of  the fire, and  placed  in a light-proof  holder to take to the camera. 3  Exposure  in the  camera  for  about  1-3  min. 4  Development,  in the same exciting solution as 2 but diluted  to  half strength. 5  Fixing in hyposulphite of soda, washing and drying.   Positive print 6  Another sheet Read more