An X-ray inspection system passes a controlled X-ray beam through the product and measures how much energy reaches a detector on the other side. Denser materials absorb more, so a contaminant that is denser than the surrounding food shows up as a difference in the image, which the system identifies and rejects.

Because detection is based on density rather than metal's electrical properties, X-ray can find a broader range of dense contaminants and is less affected by conductive packaging. The product's own density and thickness form the background against which contaminants are judged, so performance depends on how much the contaminant stands out from the food around it. This density-based approach is what gives X-ray both its distinct strengths and its particular limitations.

X-ray detection depends on density differences because the technology works by measuring how much of the beam the product and any contaminant absorb. A contaminant that is significantly denser than the surrounding food absorbs more energy and appears as a distinct area in the image; one whose density is close to the food blends in and is harder to see.

This is why dense materials like metal, glass and stone are detected well, while low-density items such as soft plastic or thin bone are challenging. It also means product thickness and composition matter, since they set the background. Understanding density contrast is central to knowing what X-ray can realistically find in a given product.

X-ray can generally detect metal, glass, stone and ceramic contaminants well, because these are denser than most foods and therefore stand out clearly in the image. This is a key advantage over metal detection, since glass, stone and ceramic are non-metallic and would not be found by a metal detector.

How reliably each is detected still depends on the contaminant's size, shape and position, and on the product's thickness and density. A small fragment in a thick or variable product is harder than a larger piece in a thin one. So while these dense contaminants are X-ray's strength, realistic performance for a specific product is best confirmed by testing rather than assumed.

X-ray can often detect stainless steel more readily than a metal detector can, because it responds to density rather than magnetic and conductive properties. Stainless steel is dense, so it tends to stand out in an X-ray image, whereas it is one of the hardest metals for a metal detector to find due to its weak signal.

This makes X-ray useful where stainless steel is a concern, particularly in wet, salty products or metallised packaging that limit metal detection. Detection still depends on the fragment's size, shape and position and the product's thickness. Where stainless steel is the critical risk, comparing the two technologies on your actual product gives the clearest answer.

X-ray struggles with contaminants whose density is close to that of the surrounding food. In practice this includes many low-density materials: soft or thin plastics, wood, cardboard, paper, some rubber, insects, hair, and thin or soft bone and cartilage. Because these absorb the beam similarly to the food, they produce little contrast and can be difficult or impossible to detect reliably.

Contaminants that are very small, flat, or oriented edge-on to the beam are also harder to register. So X-ray should not be assumed to catch every contaminant; its strength is dense materials. Knowing which contaminants are realistic for your product, and testing them, is the way to understand what X-ray can achieve.

X-ray can sometimes detect plastic, wood, insects or bone, but not reliably in every case, because these materials are often low in density and produce little contrast against the food. Hard, dense plastics may be found; soft or thin plastics frequently are not. Dense bone can show up, while thin or soft bone and cartilage may be missed. Wood and insects are generally difficult.

The outcome depends on the material's density relative to the product, its size, shape and position, and the product's thickness. It would be misleading to claim X-ray detects all of these. For any of them, the honest way to know what is achievable is to test the actual product and contaminant.

Product density and thickness strongly affect X-ray detection because they form the background against which a contaminant must stand out. A thin, uniform product lets contaminants show clearly, while a thick or dense product absorbs more of the beam and reduces contrast, making small or low-density contaminants harder to see. Natural variation in density across a product adds further difficulty.

This is why the same contaminant can be easy to detect in one product and hard in another. It also means realistic performance has to be judged for the specific product rather than in general. Testing with the actual product and its typical variation gives the most dependable indication of what X-ray can achieve.

Packaging affects X-ray inspection mainly through its density and any dense components. Most films, cartons and plastics are low in density and have little effect on the image. Denser or multi-layered packaging, metal components such as clips or seals, and thick containers absorb more of the beam and can make contaminants harder to see or create features that must be distinguished from real contamination.

Unlike metal detection, X-ray is generally not defeated by metallised film or foil, which is a key advantage. Still, the specific packaging influences image clarity and achievable detection. Reviewing the actual final pack alongside the product ensures the assessment reflects how the packed item will really appear to the system.