Acrylic paint is water-based and therefore water soluble so water can be used for thinning of the paint. But we need to be really careful as to how much water or medium to use. Adding too much water can lead to peeling and flaking of the paint. So it is best not to mix more than 30% of water to paint. But it can also depend on the quality of the paint used, the surface and also if you use any medium.
It is good to experiment yourself with the amount of water to be added. But too much water causes the acrylic polymer to lose its binding properties, resulting in the dispelling of the pigment.
We can use mediums to change the paint glutinousness while the chemical integrity remains the same. Different mediums give different effects. Since mediums have the same resin that makes the paints stick, you can add as much as required.
