If you plan to work with photo emulsion, I recommend that you purchase prepared photo emulsion from a school art supply or other commercial supplier. Follow all instructions for your personal and environmental safety when working with all art materials.

We continue to become aware of personal and downstream environmental hazards of the materials and chemicals used as art materials.

Because of downstream environmental hazards of potassium dichromate and because of the potential hazards of working with potassium dichromate, I am no longer sharing the recipe for making your own photo emulsion. A small amount of hazardous potassium dichromate was one of several ingredients.  

If you work with potassium dichromate, be sure to study the EPA (Environmental Protection Agency) regulations.  The materials may not be disposed of down sink drains.  You must have a safe way to dispose of hazardous residues.  Serious hazards to your health and safety are described in the literature. 

Comenius - European Cooperation on School Education
Chemical Safety Data: Potassium dichromate http://cartwright.chem.ox.ac.uk/hsci/chemicals/potassium_dichromate.html

MATERIAL SAFETY DATA SHEET POTASSIUM DICHROMATE pdf