Quote Originally Posted by PhotoSmith View Post
Thanks for the clarification. So why do the crystal shapes change as the pAg increases? Which of the shapes is ideal?
The pAg is the determining factor for what type of crystal forms, or that is to say, the way the silver halide falls out like snowflakes as they condense from the liquid. So, just as you can get sleet, hail and flakes from water in the air depending on the humidity and temperature, you can get cubes, octahedra and t-grains from silver halides.

The grain shape is used to control speed, sharpness and grain. T-grains are very fast because they are flat and present a huge surface to the light. Cubes can be made very small and are used in papers and in print films for fine grain and sharpness. There is a use for every type of grain, even if it is to be a foundation to grow another type of crystal.

You could make a cube and then convert it to an octahedral shape by growing something over top of it. This would then become a core shell or converted emulsion.