A dry paint brush is fluffy;
The bristles of a wet paint brush cling together.
But the bristles of the paint brush in the jar of water are wet and fluffy
Why do the two wet
brushes behave in
different ways?
Brush inside the jar
The brush in the jar is held below the water’s surface. Water surrounds the bristles, but has a little effect on their positions.
Brush outside the jar
The wet brush outside the jar is surrounded by air. Water molecules don’t cling to air, so they pull together and bring the bristles together, too.