Which of the following are typical of foreign matter that might block the openings of discontinuities if the surface of a test specimen is NOT properly cleaned?

When conducting visual testing, it is crucial to ensure that the surface of the test specimen is thoroughly cleaned. If not, various types of foreign matter can obstruct the openings of discontinuities, which significantly hinders the detection of flaws during inspection.

Paint is commonly found on metal surfaces and can easily cover cracks or other discontinuities. If the paint is not appropriately removed, the inspector will be unable to accurately assess the state of the underlying material.

Scale refers to oxidized metal that forms on surfaces during processing, often seen in forged or cast materials. If scale is present and not cleaned, it can act as a barrier that disguises defects such as pits or seams.

Core and mold material can also be an issue, particularly in cast components. Residual materials from the mold can block visual access to discontinuities, leading to potential oversights in the inspection process.

Given these points, the inclusion of all items—paint, scale, and core and mold material—captures the array of potential foreign matter that can impede a thorough inspection, verifying that all these elements can hinder the visualization of critical defects if the specimen is not properly cleaned.