What must watertight closures have for gaskets to press against?

For watertight closures to function effectively, the gaskets must press against clean, bright, unpainted, smooth surfaces. This ensures a proper seal by enabling the gasket to fully compress against the surface, minimizing the risk of leaks. Smooth surfaces reduce the chances of any imperfections disrupting the contact needed for an effective seal. Additionally, dirty or painted surfaces can create gaps or inconsistencies that can compromise the watertight integrity.

The specific requirements for the surfaces are aimed at achieving optimal sealing performance. Clean and unpainted surfaces are essential because contaminants like dirt, grime, and paint can interfere with the gasket's ability to form a tight seal. Furthermore, rough or textured surfaces do not provide the necessary contact area or pressure needed for the gasket to seal effectively, increasing the likelihood of water ingress.

Therefore, having the right type of surface is critical for ensuring that watertight closures maintain their integrity and functionality in preventing water from entering designated areas.