What is used to determine if the knife edge and gasket have continuous contact?

The chalk test is a method employed to assess whether there is continuous contact between the knife edge and the gasket. This technique involves applying a light layer of chalk on the surfaces. When the two surfaces are brought together and then separated, any areas where the chalk remains indicate a lack of contact, while areas that have had the chalk removed reflect proper sealing. This method is particularly useful because it allows for a straightforward visual confirmation of the contact point integrity, essential in applications where leaks can cause significant issues.

While the water test, pressure test, and visual inspection are useful for different assessments—it’s the chalk test that provides specific and reliable feedback about the gasket's contact with the knife edge.