What is Dye penetration test

Dye penetration test is a type of non-destructive testing. It is also known as liquid penetration test It is a widely used method to detect the defects, cracks or flaws on the surface of a material. A wide range of materials can be tested with the penetration test. 

The principle of Dye penetration test is simple. When a less viscous liquid is applied on the surface of a material the liquid will penetrate into the surface cracks by the capillary action. 

The process of Dye penetration test

In the whole process of this testing, three different liquids are used these three liquids are 

1. Cleaner 
2. Penetrator 
3. Developer 

Before these three steps, one vital step i. e. 'Precleaning' should be done. 


In this step, the workspace man is cleaned. all the dust, oil, grease particle must be removed. the impurities on the surface of the work-piece can lead to false results or false indication in the test. 

In the precleaning, many methods are used. For Example, to remove the dust or metal chips air pressure is applied to the surface. 

Some more methods like solvents, Degreasing etc. are used to remove other impurities such as oil grease etc. 

The motive of this step is to make the surface such that the defects are open to the surface and prevent false indications as a result of the test. 

After the precleaning first liquid agent i. e. The cleaner is used.


The first liquid used face cleaner. The purpose of using cleaner is to make the surface free for your it is where the test is to be performed at Pune will be applied and kept for some time. the cleaner will disintegrate the remaining dirt, dust, oil from the surface. 


The penetrant is a dye which is very bright and colorful. After the cleaning is done and cleaner evaporates, the penetrating dye is applied on the surface of the specimen the dye should have low viscosity and low surface tension so that the dye can penetrate in the cracks easily. 

The smaller cracks will take more time to penetrate than the bigger surface cracks. 
The access dye on the surface has to be removed. This is also a very important step. 


The developer is applied on the surface where the penetrant was applied previously. The developer will have the capability to absorb the penetrant from the cracks. When the developer will absorb the penetrating agent from the cracks it will come out to the surface and the cracks indication will occur on the surface. the Developer can be in the form of liquid or in the form of powder it depends on the type of penetrant used.