A wash is simply accenting areas to provide depth using a very translucent degree of pigment using a darker color with large parts of water or medium. Basically, it's staining. <div>
</div><div>For instance, you have the mold lines in the mud guards. There's a few ways to produce depth in the mold lines. One being, to actually brush paint in the lines with precision or a micron pen, or radiograph pen. Then there's the wash. A simple watery solution of pigment brushed over the mold area and lightly wipe away from the highest point leaving the wash solution in the seams. In many cases, it isn't necessary to wipe anything, but for that example....you do. Leaving traces of your washing isn't always ideal unless you wan't it to looks like stains.  </div>