Comprehensive Analysis of Inspection and Testing Standards for Ceramic Products: Quality Control Guidelines for Plates, Bowls, Cups and Plates

March 26, 2026

Part One: Inspection Standards for Disk Products
I. Surface Defect Inspection
Visible surfaces (those exposed and directly visible on the product):
Debris: No more than 2 pieces
Defective glaze: No more than 2 pieces
Glazing: No more than 2 layers
Black dots: No more than 2 (each black dot has a diameter of no more than 1mm)
Overall assessment: None of the aforementioned defects can exist simultaneously for more than 3 instances.
Non-visible areas (such as the bottom and back of the product):
Debris: No more than 3 pieces
Defective glaze: No more than 3 pieces
Glaze application: No more than 3 layers
Black dots: No more than 3 (each black dot has a diameter of no more than 1mm)
Overall assessment: None of the aforementioned defects can exist simultaneously for more than 4 instances.
Inspection method: Under natural light, use a 10x magnifying glass for visual inspection. The inspector should conduct the inspection item by item or by sampling according to the AQL standard.
II. Deformation Test
Place the plate flat on a smooth testing surface and check if it has deformed:
For discs of 9 inches and smaller: Slide a one-yuan RMB coin along the edge of the disc. If the coin can easily pass through the gap between the disc and the flat surface, it is considered不合格.
For discs larger than 9 inches: Place two one-yuan Chinese coins overlapping each other and slide them along the edge of the disc. If the coins can easily pass through the gap between the disc and the flat surface, then it is considered不合格 (unqualified).
Note: This test must be conducted on a standard flat surface. The one-yuan coin is measured against the one-yuan denomination of the RMB.
III. Bottom Inspection
Finishing quality:
When touching the bottom with your hand, there should be no obvious rough feeling. The qualified products should have a smooth surface.
The polishing should be uniform and there should be no dented areas. If there are obvious dents, it is considered as unqualified.
Black background check:
The bottom must not have any obvious black background.
A slight black background is acceptable, but if the black area exceeds one quarter of the total bottom area, it will be judged as unqualified.
Base marking position:
The bottom mark should be placed in the very center of the bottom.
If there is a significant deviation, it will be judged as unqualified.
The diameter of the explosion range shall not exceed 2.5mm (including 2.5mm). If it exceeds this limit, it will be deemed as unqualified.
IV. Dimension Inspection
For disk products of 9 inches and below: The dimensional deviation must not exceed 3% of the original specification.
For disk products larger than 9 inches: The size deviation must not exceed 2.5% of the original specification.
Testing method: Use a standard caliper or ruler for measurement, and record the actual dimensions and compare them with the order specifications.
V. Shape and Appearance
The shape of the product must be exactly in accordance with the customer's requirements.
The appearance should be kept clean and tidy. If the product becomes too dirty, it should be notified to the factory for improvement. In severe cases, it should be returned.
VI. Packaging Inspection
The packaging must not be loose and must comply with the requirements for export packaging.
Facilitate transportation and handling, ensuring that the products are not damaged during the logistics process
Part Two: Inspection Standards for Bowl Products
I. Surface Defect Inspection
Visible defects:

Debris: No more than 2 pieces
Defective glaze: No more than 2 pieces
Glazing: No more than 2 layers
Black dots: No more than 2 (each black dot has a diameter of no more than 1mm)
No more than three types of defects can coexist at the same time.
Non-public meeting:
Debris: No more than 3 pieces
Defective glaze: No more than 3 pieces
Glazing: No more than 3 pieces
Black dots: No more than 3 (each black dot has a diameter of no more than 1mm)
No more than four types of defects can coexist at the same time.
II. Inspection of Bottom Disk Deformation
Place the bottom disk flat on a smooth inspection table surface.
Slide a one-yuan RMB coin along the edge of the plate.
If the coin can easily pass through the gap between the disc and the flat surface, it is considered disqualification.
III. Inspection of the Center Hole and Compatibility
Design of the center hole: The center hole of the base plate should not be too large or too shallow.
For the test: If the cup can slide out of the center of the moon with just a slight movement, then it is determined that the base plate is disqualification (unqualified).
Dish and cup compatibility: The porcelain color of the cup and the base plate must be the same; there should be no color difference.
Glazed products: Such glazed products must not have any color difference issues among similar products.
IV. Inspection of Cup Mouth Shape
The cup mouth shape must be a perfect circle, a perfect square, or a specific shape as per the customer's requirements.
If the cup rim is not round, not straight or does not meet the customer's requirements, it will be judged as unqualified.
V. Inspection of Handle and Connection
There shall be no cracks at the connection point between the handle and the cup body (commonly known as a cracked handle)
The position of the hand must be correct and not tilted.
VI. Bottom Inspection
Finishing Quality:
When touching the bottom with your hand, there should be no obvious rough feeling. The qualified products should have a smooth surface.
The polishing should be uniform and there should be no large depressions or scratches.
Black background check:
A slight black background is acceptable. However, if the black area exceeds one quarter of the total bottom area, it is considered不合格 (unqualified).
Base marking position:
The bottom label of the cup or plate should be placed in the very center of the bottom.
Any significant deviation or excessive blooming is considered as unqualified.
VII. Dimension Inspection
The dimensional deviation of cups and plates shall not exceed 3% of the original specification.
VIII. Packaging and Appearance Inspection
The packaging must not be loose and must comply with the requirements for export packaging.
The appearance of the product should remain clean and tidy.
The shapes of all cups and plates must be in accordance with the customer's requirements.
Part Four: General Requirements for Ceramic Product Inspection
I. Classification and Determination of Defects
According to the inspection standards for ceramic products, defects can be classified based on their severity:
Defect Categories Definition Judgment Criteria
Fatal Defects Defects that may cause harm to users or violate regulations (such as sharp edges, excessive lead and cadmium content) Zero tolerance. Any discovery results in the entire batch being judged as non-conforming.
Major Defects Defects that affect the product's functionality or have obvious appearance issues (such as severe deformation, excessive deviation of the bottom label) Judged according to the AQL standard
Minor Defects Slight appearance flaws that do not affect usage (such as a few pieces of debris, slight black spots) Judged according to the AQL standard
II. Sampling Plans
Determine the sampling quantity and acceptance level according to the AQL (Acceptable Quality Limit) standard
For critical projects (such as deformation tests and size measurements), it is recommended to adopt the general inspection level II.
For the inspection of appearance defects, the general inspection level I can be adopted.
III. Requirements for Migration of Lead and Cadmium Heavy Metals
As a food contact material, ceramic products must meet the limits for harmful substances:
Container type Lead leakage limit Cadmium leakage limit
Class 1 containers (flat shallow containers, depth < 25mm) 0.8 milligrams/square decimeter 0.07 milligrams/square decimeter
Class 2 containers (bowls, water jugs, etc. with depth) 4.0 milligrams/liter 0.3 milligrams/liter
Class 3 containers (storage tanks, capacity > 3 liters) 1.5 milligrams/liter 0.1 milligrams/liter
During inspection, it is necessary to verify the third-party inspection report or certification certificate provided by the factory to ensure that the products meet the requirements of the target market (such as national standard GB 4806, US FDA, EU LFGB).
Part Five: Linkage between Factory Inspection Audit and Certification
I. Supplier Capability Assessment
During the factory inspection audit, ceramic product suppliers need to focus on the following assessment:
Raw material control: Purchase and inspection records of porcelain clay, glaze, and pigment
Production process control: Quality control points for each process such as molding, drying, glazing, and firing.
Testing capabilities: Equipment and personnel qualifications for size measurement, deformation testing, and appearance inspection
Lead and Cadmium Control: Measures for Controlling Harmful Substances in Raw Materials, Glazes, and Pigments
Packaging management: The standardization of packaging materials and packaging methods, as well as their compatibility for transportation.
II. Product Certification Requirements
For ceramic products to enter different markets, they must comply with the corresponding certification standards:
Target Market Certification Requirements Inspection Focus
Chinese Market GB 4806 food contact material safety standards, CCC certification (for specific products) Lead and cadmium migration levels, appearance quality, size deviation
European Market LFGB certification, CE mark, REACH regulations Maximum levels of harmful substances, food contact safety
American Market FDA certification, California 65 proposal Lead and cadmium limits, product safety
Japanese Market JIS standards, Food Hygiene Law Lead and cadmium migration levels, product performance
III. Continuous Improvement
Quality issues discovered during inspection should be promptly reported to the supplier.
Repetitive issues should be followed up with factory inspections to implement corrective measures.
Establish a quality traceability record to support product certification audits
Regularly update the inspection standards to adapt to the changes in regulations in the target market.