Visual Testing 101: A Look at NDT’s Oldest and Most Common Technique

The non-destructive testing industry is large, diverse, and vital to the success of many Canadian businesses. With varied techniques like magnetic particle testing, dye penetrant testing, and radiographic testing, the NDT field plays a vital role in countless construction, pipeline, and manufacturing projects.


But did you know that there is one technique at the heart of all NDT techniques? Visual testing is the first step in any non-destructive testing process. Whether your project needs ultrasonic testing or a concrete X-ray, NDT professionals will always perform a visual test before proceeding.

In this blog, we’ll tell you what you need to know about this integral part of the non-destructive testing process.

What Is Visual Testing?

Visual testing is the oldest and most common technique in the non-destructive testing field. Before performing any other test, NDT professionals perform visual examinations on all pipe castings, machine components, and ground elements.

During a visual inspection, a tester does more than just look at an object. The tester touches the object’s surface, feeling for imperfections. The tester will also observe the object or surface as it twists and shakes, searching for abnormalities in its movements.

Purpose of Visual Testing?

Visual testing sounds basic, and to an extent it is. But even though it is one of the more basic NDT techniques, it is a fundamental part of the NDT process.

Though basic, a visual inspection allows the tester to identify flaws in pipe welds, concrete foundations, and machine components. By identifying potential problems in these areas, the tester can then determine the best course of action for the rest of the testing process. This knowledge also prevents accidents and injuries during the NDT process.

Common Industries

Like other NDT techniques, visual testing is used in a wide variety of industries. Some of the most common include:

  • Power generation
  • Structural steel
  • Petrochemical
  • Aerospace
  • Automotive

Common Applications

At some point or another, all NDT techniques require a visual test. We’ve explained a few of these situations below:

  • Liquid penetrant testing requires visual testing, as a tester must use dye to identify surface flaws.
  • Radiographic and X-ray testing both require an NDT professional to locate blockages and corrosion in an object or on a surface.
  • Magnetic particle testing involves the identification of surface discontinuities and imperfections. As part of this inspection, a tester must be able to visually identify leaks, surface contaminants, and magnetized parts.
  • Pipe and weld examinations employ visual testing to determine the soundness of joints, openings, sockets, and bevels. NDT professionals also use visual tests to find cracks, slags, undercuts, and arc strikes in pipes and welds.

Advantages of Visual Testing

In addition to helping prevent accidents and injuries during the NDT process, visual testing has several advantages. Visual testing is:

  • The simplest non-destructive testing method to learn. Because they require few technical and interpretive skills, visual testing certification classes are low-cost and short.
  • The quickest most cost-effective NDT method. If you want to ensure your project goes smoothly, you can’t go wrong with visual testing.
  • One of the most reliable NDT methods. By incorporating visual tests throughout the testing process, your project will require few repairs in the future.
Basic Requirements of Visual Testing

Although visual testing appears straightforward, it does have a few basic requirements. These requirements include:

  • Visual acuity. Only NDT professionals with 20/20 vision can perform visual tests. In fact, visual testers must pass annual eye exams before they can perform the tests. These eye exams check for problems with depth perception and colour blindness.
  • Adequate lighting. Light is essential to the visual testing process. Without an adequate amount of light, a tester won’t be able to examine an object or monitor a surface’s movements.
  • Access to the testing object or surface. In order to thoroughly inspect an object, a tester must be able to get close to an object. Ideally, a tester should be able to come within half a metre of an object. If this isn’t possible, the tester will have to use an examination aid.

Examination Aids

Unfortunately, objects and surfaces that need inspect are not always easily accessible. Other objects may obscure them from view, or they might sit underneath another surface. In any case, testers can use several examination aids to facilitate the visual test. These aids include:

  • Boroscopes, which are pan and tilt cameras that fit in small spaces. They illuminate dark spaces, such as gaskets and cracks, to provide 360° images.
  • Micrometers, which scan an object to find the thinnest point.
  • UV lights, which aid in magnetic particle testing.
  • Magnifying glasses and mirrors, which help testers see surfaces at different angles, allowing them to form a more complete assessment of an object.


Even though visual testing is one of the less technologically advanced NDT methods, it is a vital part of any testing method. Talk to our team of specialists at 20/20 NDT for additional information on how to incorporate this technique into your worksite.