PE, here's a copy of a gelatin formula I found an the web as a lab experiment a couple days ago. I'm curious how you would rate it, especially for sensitivity, quality, and longevity.
With the lights on, dissolve 2.4 g of potassium chloride and 1.2 g of potassium bromide in 100.0 ml of distilled water. Place this solution on a stirrer hot plate and bring the temperature to 35ºC. Add 20.0 g gelatin. Set this aside to thicken. In another beaker dissolve 6.0 g of silver nitrate in 60.0 ml of distilled water. Assemble the constant temperature apparatus shown below. Run the hot water for a while to ensure temperature is about 50ºC. Heat the potassium chloride-gelatin mixture in the beaker to about 50ºC.
The remainder of this experiment must be done with a safety light as the photographic emulsion is extremely light sensitive once it is prepared. Add the silver nitrate solution slowly, with continued stirring, to the gelatin-halide mixture. The rate of addition should be no greater than 1 mL per 3 seconds. Ripen at 50C for 2 hours while stirring. At the end of this digestion period, add another 10.0 g of gelatin. Once this has dissolved, you can chill the emulsion with an ice bath. If necessary, the experiment can be stopped at this point. Wrap the emulsion beaker with foil, label and store in the refrigerator.
If the emulsion is shredded and washed, then cold tones will be observed. If it is left unwashed, warm tones will be obtained. The emulsion should now be melted and with continuous stirring, held at approximately 60ºC for 1½ hours. At the end of this second digestion period. 0.125 g of chrome alum (dissolved in a minimum of H2O) can then be added as a hardener, but the alum will make the gelatin very thick.