How to reuse vacuum bottles

When the vacuum bottle is pressed, the piston inside will move upward in the bottle. When all the contents of the vacuum bottle are squeezed out, the piston will move to the top of the bottle. When the contents of the bottle are used up, you can remove the pump head from the vacuum bottle and use a hard object to push the piston in the bottle back to the bottom. Then reassemble the vacuum bottle and you can reuse it.