Explainer · Defects and grading
Are rough-shelled eggs a defect or just appearance?
A rough-shelled egg has a shell surface that is uneven or sandpaper-like instead of smooth. Brazil's RIISPOA requires a smooth, clean, intact shell for Class A (art. 225, I), so roughness takes the egg out of that class even when the egg is harmless. A camera sees roughness as texture, not colour, so the rule must be written down and calibrated on real eggs.
Updated · 4 min read
What is a rough-shelled egg?
A rough-shelled egg has a shell surface that is uneven and abrasive, feeling and looking like sandpaper. Unlike a crack, the shell is still whole; unlike a stain, nothing sits on top of it. The difference lies only in the texture of the shell itself.
In practice, graders call an egg rough when that texture runs across the shell, rather than a single line or a localised mark. That distinction decides which defect rule applies.
Why does a rough shell take an egg out of Class A?
Because Class A requires a shell “of normal shape, smooth, clean, intact” (RIISPOA, art. 225, I). Roughness puts the shell outside the smooth shell that the rule describes, so the egg leaves Class A even with no crack and no dirt.
The rule does not say how rough is too rough. That decision belongs to the operator and must be written down: without a written criterion, two operators can sort the same egg differently.
| Situation | Destination | Basis |
|---|---|---|
| Smooth, clean and intact shell | Class A, if it meets the other requirements | RIISPOA, art. 225, I |
| Rough shell, no crack or dirt, harmless | Class B, for industrial use only | RIISPOA, art. 226, I and its single paragraph |
| Rough shell with a crack or dirt | Follows the rule for that defect | RIISPOA, arts. 227 and 228 |
Class B eggs go exclusively to industrial processing (RIISPOA, art. 226, single paragraph). See Brazil's Class B eggs and cracked eggs.
How does a camera see a rough shell?
A camera sees a rough shell as texture, not as colour. Roughness creates small brightness changes spread over the shell, while a stain forms an area and a crack forms a thin line. The average colour of a rough egg can match a smooth one, so the signal sits in the brightness pattern.
Lighting changes the picture. Raking light picks out every irregularity and makes roughness look stronger; diffuse, even light softens it. The same egg can pass under one light and fail under another, so test the criterion under the real lighting of your line, not only on the bench. See lighting for egg inspection.
Vigiovo has no class for rough shells: it grades each egg as clean, dirty, cracked or unverified. Small texture details can therefore be read as dirt or as a crack line, and calibration with rough eggs from your own line shows whether that happens. Details in how it works.
How do you tell roughness from dirt and cracks?
Look at what sits on the shell and at the pattern of the irregularity. Dirt is material on top of the shell, a crack is a line that breaks the shell, and roughness is a continuous texture with no line and nothing on it.
- Dirt: material from outside the shell, such as faeces, blood or soil. See dirty egg.
- Crack: a thin, elongated line that breaks the shell. For cracks too fine to show under normal light, see hairline crack.
- Rough shell: an irregular texture spread over the shell, with no defined line and nothing on top of it.
Raised white spots look similar at first glance. See calcium deposits on eggshells.
What should the team define for rough shells?
Set the criterion before the line runs, with real photos and a named owner. The steps are:
- Collect photos of rough eggs from your line, from mild to severe, as a reference.
- Write down what is acceptable for Class A and what moves the egg to Class B.
- Pick one example each of roughness, dirt and crack, and label them clearly.
- Test the criterion under the real lighting of the line and record the date it was set.
Frequently asked questions
Can a rough-shelled egg be sold as Class A?
- No, if the shell is not smooth. RIISPOA requires a smooth, clean, intact shell for Class A (art. 225, I). A rough egg with no crack or dirt usually counts as Class B, which goes exclusively to industrial processing (art. 226).
Is a rough shell the same as dirt?
- No. Dirt is material from outside sitting on the shell, such as faeces, blood or soil. A rough shell is an irregularity of the surface itself, with nothing on top. Because a camera can read texture as a stain, the dirt rule must be calibrated with rough eggs from your line.
Can a camera measure how rough a shell is?
- A camera sees the texture, but the Brazilian rule does not set any measure of roughness, so the threshold is the team's decision. Vigiovo has no class for rough shells, so calibration on real eggs shows which class roughness ends up in.
Sources
- Decreto nº 9.013/2017 (RIISPOA), Presidência da República (Brasil)
How Vigiovo helps
Vigiovo grades eggs on the conveyor as clean, dirty, cracked or unverified, in real time, with deterministic computer vision: every decision comes with the measurements behind it, on an ordinary CPU.