To measure the physical properties of a coating, you can perform the following tests:

1. Varnish film thickness: The most accurate method is to weigh a sample of a given surface before and after removal of the varnish film. Normally a circular disk with a surface area of four inches square is used.
2. Drying: To determine if the varnish has cured properly, perform the “mec” (methyl ethyl ketone) test. Soak a cotton swab in acetone or methyl ethyl ketone and rub the varnish with it. The more the film resists friction with cotton, the higher the polymerization rate.
3. Hardness: You can measure the hardness of the varnish with a durometer. This test determines the resistance of the coating to penetration or deformation.
4. Porosity: To measure the porosity of the coating, you can use a water absorption test. An insufficiently cured varnish will show a whitish haze after treatment, due to water absorption.
5. Chemical resistance: Perform tests for acid resistance, process resistance and impermeability to sulfide ions to evaluate the chemical resistance of the coating.
6. Flavor: Check if the varnish affects the flavor of the packaged food by performing sensory tests.

Please note that test conditions, frequency and acceptance criteria may vary depending on the type of coating and the specific requirements of the application.

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