Can I use salt water with watercolours?
Yes, you can use salt water with water colours. But remember, table salt (or salt water)is highly hydrophobic. Salt repels water. Anywhere salt is present on your paper it will repl water way from the area. The water colour pigments floating in your solution will concentrate around the salt particles. As the water is pushed away from the salt you will get concentrated areas of pigments in those areas where salt particles are present. So if you are looking to achieve a spotted texture on the surface of your water colour painting salt is a good choice.

As an experiment try sprinkling some table salt on the surface of your water colour painting, the sprinkled salt will create a more pronounced effect as the larger salt crystals in the table salt will repel a larger amount of water.

When done painting clean your brush with regular tap water. This will keep a layer of salt precipitating out on the hairs of your brush as the salt water drys.