Valves

the valve should open and shut quite freely when air passes through the blowstick

The valve must sit flush at the bottom of the blowstick. The valve should be closed, i.e. covering the hole when not being blown.

Once air is blown through the blowstick, the valve should open, allowing the air to pass into the bag. Once the blowing stops, the valve should close and not allow any air to pass back up through the blowstick. The valve should open and shut quite freely. However, a little vaseline on the underside of the valve is often required to help form the seal.