Liquid penetrant testing is a non-destructive testing method used to identify surface defects in materials. It involves applying a liquid penetrant to the surface of the object, allowing it to seep into any cracks or voids. After a specified dwell time, the excess penetrant is removed, and a developer is applied to draw out the penetrant from the defects, making them visible. This technique is widely used in various industries, including aerospace, automotive, and manufacturing, due to its effectiveness in detecting flaws such as cracks, porosity, and laps. It is suitable for a range of materials, including metals and plastics, and is valued for its simplicity and cost-effectiveness.