アラビアガム
To sensitize the gum arabic it must first be placed in contact with ammonium or potassium dichromate. Gum arabic is not photosensitive by itself. To clear the chromic acid, the print is washed in 1% potassium metabisulfite after proper development in water. Interested individuals should read up on the process before attempting, as the chromic acids are very dangerous to work with.