# Calcium deposits on eggshells: how should they be graded? > Calcium deposits are small, hard, pale raised spots on the shell, formed by excess calcium carbonate on the surface. RIISPOA requires a smooth shell for Class A (art. 225, I), so a visible deposit takes the egg out of that class. A camera can mistake them for dirt because of their colour and the shadow they cast, so calibration on real eggs from your line decides the grade. Updated: 2026-10-09 · URL: https://vigiovo.com/en/resources/calcium-deposits-on-eggshells · Português: https://vigiovo.com/recursos/depositos-de-calcio-na-casca.md ## Key takeaways - Calcium deposits are part of the shell itself, not dirt or a crack. - RIISPOA requires a smooth shell for Class A (art. 225, I), so a visible deposit takes the egg out of that class. - A deposit with no crack or dirt is harmless and tends to go to Class B (art. 226, I). - On camera, a pale spot on a brown shell and the shadow of a bump can both be read as a stain. ## What are calcium deposits on an eggshell? Calcium deposits are small, hard, pale elevations on the surface of the shell, formed by excess calcium carbonate while the shell is being built. In English they are often called pimples. They are irregularities of the surface, not cracks or dirt. They usually appear as isolated spots, and the shell around them can look normal. ## Does a calcium deposit take an egg out of Class A? Yes, when the deposit is visible. Class A requires a shell “of normal shape, smooth, clean, intact” (RIISPOA, art. 225, I), and a raised area on the shell means the surface is no longer smooth. The rule does not say how many deposits, or of what size, are acceptable. The team has to define that criterion in writing, just as it does for rough shells (see [rough-shelled eggs](https://vigiovo.com/en/resources/rough-shelled-eggs)). **Where the egg goes, in practical reading of RIISPOA** | Situation | Destination | Basis | | --- | --- | --- | | Smooth shell, no deposit | Class A, if it meets the other requirements | RIISPOA, art. 225, I | | Deposits, no crack or dirt, harmless | Class B, for industrial use only | RIISPOA, art. 226, I and its single paragraph | | Deposits with a crack or dirt | Follows the rule for that defect | RIISPOA, arts. 227 and 228 | ## How can a camera mistake a deposit for dirt? A camera can confuse a deposit with dirt for two image reasons. The deposit is paler than the brown shell, and that difference in colour can be read as a stain. The raised area also casts a shadow when light comes from the side, and the shadow can look like a dark mark. - **Colour**: a white deposit on a brown shell has a different colour from the shell, and a colour-deviation measure can count it as a stain. - **Shadow**: a raised area under raking light throws a shadow to one side, and that shadow can be read as dark dirt. Raking light strengthens both effects. Diffuse, even light reduces the shadow of the bump, so it is the first adjustment to test before touching the limits. See [lighting for egg inspection](https://vigiovo.com/en/resources/lighting-for-egg-inspection) and [glare and false dirty grades](https://vigiovo.com/en/resources/glare-and-false-dirty-grades). ## How does calibration separate a deposit from dirt? Calibration separates the two using real eggs from your line, including ones with deposits, labelled by your team. In a pilot, the system is calibrated on images from your own conveyor, and the dirt and colour thresholds are adjusted until the result matches the labels. Vigiovo measures dirt as area below a shading surface fitted to each egg, and measures colour deviation in Lab space. It has no class of its own for deposits: they fall into clean, dirty, cracked or unverified. Testing with eggs that carry deposits shows which class they land in, and whether that is the class your team wants. See the [calibration checklist](https://vigiovo.com/en/resources/egg-grader-calibration-checklist) and [Lab colour space](https://vigiovo.com/en/resources/lab-colour-space-for-shell-stains). Details in [how it works](https://vigiovo.com/en/how-it-works). ## What should you record about deposits on the line? Write the rule down before the line runs, with examples of each case. The steps are: 1. Photograph real deposits from your line, from small to clearly visible, as a reference. 2. Write down whether a visible deposit is a reason to leave Class A, with the date the rule was set. 3. Separate deposit, dirt and crack examples, so the camera and the team use the same reference. 4. Test the rule under the real lighting of the line and check that eggs with deposits land in the chosen class. ## Frequently asked questions ### Can an egg with a calcium deposit be Class A? No, once the shell is no longer smooth. RIISPOA requires a smooth, clean, intact shell for Class A (art. 225, I). An egg with visible deposits but no crack or dirt usually counts as Class B, which goes exclusively to industrial processing (art. 226). ### Is a calcium deposit dirt? No. Dirt is material from outside sitting on the shell, such as faeces, blood or soil. The deposit is part of the shell itself. Even so, a camera can read it as a stain because of its colour and shadow, so calibration must include eggs with deposits. ### How should a camera handle calcium deposits? Through calibration with eggs from your line that carry deposits, labelled by your team and lit as they are in production. Dirt and colour thresholds are adjusted until the result matches the labels. Vigiovo has no class of its own for deposits, so the test shows which class they fall into. ## Sources - [Decreto nº 9.013/2017 (RIISPOA)](https://www.planalto.gov.br/ccivil_03/_ato2015-2018/2017/decreto/d9013.htm), Presidência da República (Brasil) ## Read next - [Body-checked ('fissured') eggs: why they can be Class A](https://vigiovo.com/en/resources/body-checked-eggs.md) (Explainer, 2026-10-09): What a body-checked (fissured) egg is, why internal cracks that only show on candling can be sold as Class A, and why cameras miss them. - [Shell colour variation isn't dirt: how to tell them apart](https://vigiovo.com/en/resources/shell-colour-variation.md) (Explainer, 2026-10-09): How to separate natural shell colour and speckling from adhering dirt in egg grading, and why comparing each egg with its own shading avoids false dirty grades. - [How to identify cracked eggs: types, methods and rules](https://vigiovo.com/en/resources/how-to-identify-cracked-eggs.md) (Guide, 2026-10-09): What a cracked egg (check) is, how it differs from a leaker, which methods detect each kind of crack and where cracked eggs must go under the regulations. ## 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. https://vigiovo.com/en/how-it-works.md 4 min read.