China Inspection and Quarantine, Factory Inspection, Certification, Testing, and Inspection Standards | How to Inspect the Quality of Everyday Glasses?

Glass is an indispensable material in our daily lives. From common glass cups to decorative glass curtain walls, glass products are widely used in various fields, providing vital support for modern life and the development of civilization. To ensure the quality and safety of glass products, brands, buyers, and retailers often rely on professional third-party inspection companies to conduct systematic inspections of glass products. This article will briefly explain how to judge the quality of glass cups and how to distinguish between good and bad double-walled glass cups, drawing on industry inspection standards.

1. Basic concepts related to glass

Glass is an amorphous, inorganic, non-metallic material typically made from quartz sand, soda ash, and limestone through high-temperature melting, forming, and cooling. Its primary components are silicon dioxide and other metal oxides, resulting in excellent light transmittance, chemical stability, and insulating properties. Common flat glass, a soda-lime silicate system, offers excellent light transmission, thermal insulation, sound insulation, and climate resistance. Its physical properties, such as transmittance, softening temperature, and coefficient of thermal expansion, are governed by national or international standards, and performance testing is often conducted against these standards during inspection .

2. Inspection methods and quality judgment of ordinary glass cups

During the inspection process, the quality assessment of glassware mainly includes material, thickness, appearance and workmanship. The following inspection items are usually required:

1. Material purity inspection

The inspector needs to carefully check whether the cup body has the following defects, which are also the focus of factory inspection :

• Lines : surface or internal stripes, fine lines need to be observed against light;

• Bubbles : Material bubbles or operating bubbles, pay special attention to whether they are easy to break or cause structural cracks;

• Sand : Unmelted particle impurities may cause the glass to crack. Focus on inspecting the bottom of the cup and the brushed cover area.

2. Thickness uniformity inspection

Inconsistent thickness can affect product safety and thermal insulation performance. When inspecting the glass, hold it up to the light and ensure uniform light transmission throughout, with no noticeable differences in brightness or darkness. The base should be slightly thicker, but not excessively so, and the walls should be uniform. You can also tap the glass with your finger to determine its uniform and solid structure by the sound it makes.

3. Appearance and styling inspection

During the inspection process, the following should be evaluated:

• Is the surface smooth, without mold marks, air holes, etc.?

• Whether there are cracks, scratches or geometric deformations;

• Whether the structure is coordinated, such as the fit between the cup lid and the cup body, and whether the style of the entire product is consistent.

This inspection is not only related to aesthetics, but also directly affects the user's feel and safety of use. It is an important basis for judging whether a batch of goods meets the standards.

3. Key points for quality inspection of double-layer glass cups

Double-walled glass cups are popular for their heat preservation and anti-scalding properties. Besides the inspection requirements for ordinary cups, special attention should be paid to their sealing, heat preservation performance, and structural integrity:

1. Brand and qualification verification <br>It is recommended to give priority to reputable brands. When inspecting the goods , it is necessary to verify the manufacturer's qualifications, quality certification and factory inspection report to ensure that the product source is reliable.

2. Workmanship and structure inspection <br>Check the glass layer thickness under light to see if it is uniform, without overall distortion, bubbles or impurities; the interface should be smooth and free of burrs, and the cup body should not be skewed or uneven.

3. Sealing performance test <br>The airtightness can be tested by filling it with water and turning it upside down to check for leaks. This is a common inspection method that simulates actual use.

4. Verification of thermal insulation performance <br>In actual testing , equal amounts of hot water are usually poured into multiple cups under the same environmental conditions, and a thermometer is used to record temperature changes. Those with good thermal insulation performance should have a slower temperature drop.

4. The role of professional inspection companies in glass product quality inspection

Professional third-party inspection companies usually implement full-process quality control of glass products, from factory inspection and assessment to finished product sampling, based on international standards (such as ISO), industry specifications, or specific customer requirements. Inspection content covers:

• Appearance defect inspection (AQL standard sampling)

• Size and thickness measurement

• Thermal stability and thermal shock resistance test

• Sealing and thermal insulation performance test

• Packaging and labeling verification

We also use professional equipment such as calipers, temperature recorders, light boxes, etc. to complete objective evaluations and ultimately issue authoritative inspection reports to provide customers with a basis for decision-making on acceptance, rework or return.

V. Summary

Although glassware is an everyday item, its quality directly impacts both user experience and safety. A systematic inspection process and scientific quality testing methods can significantly reduce procurement risks and enhance product competitiveness. Whether it's a standard glass or a double-walled glass, rigorous inspection and quality control ensures it meets design specifications and consumer expectations.