I can’t help but think this is common sense. When a ketchup bottle is almost empty, you don’t have the seal to ensure it comes out smoothly, so the air catches

I can’t help but think this is common sense. When a ketchup bottle is almost empty, you don’t have the seal to ensure it comes out smoothly, so the air catches it which is moving at a higher rate of speed, and subsequently goes all over the place due to the unrestricted inside pressure.