Printing white ink is the hardest ink to print. On t-shirts you end up having to do two passes while doing a partial cure between passes. This ensures you get proper coverage. Unfortunately this also adds a lot of ink and can make the garment heavy.
On Can coolers, it is not that feasible to print 2x and cure, so most companies add a little puff to the ink. Puff is a chemical that literally makes the ink “puff up” so it stands up. You can add a lot of puff and come up with some pretty neat effects.
If you look closely at this image, you can see the ink stands up on the can cooler.
Here is an example of when you add a lot of puff. It looks pretty cool.
But you can see how it would fill in with smaller areas.