For a high contrast negative, you can use Lith film processed for 3 minutes in lith developer. Rinse for 30 seconds. Exposed to a 7 1/2 watt bulb at 120cm (4 feet) for 30 seconds. Process again for 2 minutes.For lower contrast, duplicate the negative on Kodak fine grain positive (old book ). Process for 1 minute in paper developer. Put in a tray of water for 30 seconds. Expose to a 25 watt bulb at 120 cm (4 feet) for 15 to 30 seconds. Develop for another minute.By doing the solarization at 25% to 50% of the processing time will give the best results.