This effect is so easy to create and yet so effective. It is one of my favourite.
Of course there are lots of factors that will determine the final outcome.
The type of salt used is one. Experiment with table salt, sea salt, rock salt, and dishwasher salt.
Drying temperature will effect how fast the piece dries, and by that, effect how much time the salt has to work it's magic.
The wetness of the fabric will also have an effect.
Now the thing to remember is to brush off the salt and heat set the paint BEFORE rinsing out the fabric to get rid of any salty residue.
Here are some I completed earlier!