A method and apparatus for testing the porosity of an object, such as a secure instrument having a substrate, visual data, and a security feature, is disclosed. The method and apparatus include a fluid source, a gasochromic material, an excitation source configured to excite the gasochromic material, and a detection device configured to sense changes in emissions from the gasochromic material after it is contacted with the fluid and excited by the excitation source. The object is configured to fit within a space between the fluid source and the gasochromic material such that when the fluid is emitted from the fluid source, at least a portion of the fluid is configured to flow through the object before contacting the gasochromic material.