I like the fairly shallow pet food cans for holding encaustic paint since they heat up quickly. I f you use a taller can, like a tomato paste or regular soup can, it would be hard to see the color and if you fill it to the top - it would take forever to heat up and become workable. If you don't own a pet, I would reach ou t to friends who have pets and ask them to save some  tins for you!