ASTM C738 Standard Test Method for Lead and Cadmium Extracted from Glazed Ceramic Surfaces

Get Certified ASTM C738 Testing for Reliable Ceramic Food-Contact Safety 

Certification confirms that glazed ceramic products meet requirements in the applicable ASTM C738 standards, including limits of extractable lead and cadmium in foods. ASTM C738 certified testing indicates the amount of metals that are leached out from the product prior to approval by the manufacturer for tableware, cookware, or other food-contact ceramic distribution. Testing and certification verify compliance with ASTM C738 requirements and minimize the chance of regulatory non-compliance and consumer health exposure. 

ASTM C738 is used primarily to determine the amount of lead and cadmium that is extracted from glazed ceramic ware under controlled acid-leaching conditions. It is utilized in industries as a test for food contact safety, quality control, and consumer product evaluation.

The scope of ASTM C738 includes 

• Material type: Ceramic wares, glazed, including tableware, cookware, mugs, plates. 
• Purpose: Determination of extractable lead and cadmium in feed, feed processing residues, and water. 
• Properties evaluated: Level of leachable cadmium and lead. 
• Testing Method: Testing leaches the glazed surface is leached with 4% acetic acid for 24 hours. Flame atomic absorption spectroscopy measures the extracted lead and cadmium. 
• Result: The concentration of lead and cadmium is reported in parts per million (ppm). 
• Test Limitations: The test standard only addresses lead and cadmium elements and does not assess other leachable elements. 
• Use conditions: The amount of lead and cadmium released depends on the extraction temperature and duration. 
• Applications: Tableware and cookware safety compliance, consumer ceramics quality control, food-contact regulatory testing, and ceramic glaze formulation development.  

What are the Uses of ASTM C738 Testing?

ASTM C738 is used to evaluate the amount of leachable lead and cadmium in glazed ceramic ware exposed to controlled acidic conditions. The results are then sent to the manufacturers for compliance with regulations and for the evaluation of the ability of a glaze formulation to reduce the release of toxic metals. This standard-

• Evaluates the lead content of glazed ceramic surfaces that may contribute to extractable lead.
• Artificially accelerates the release of lead and cadmium by leaching with acetic acid.
• Evaluates the leaching characteristics of cadmium under laboratory temperature conditions.
• Helps verify the safety and hygiene standards for food contact surfaces.
• Supports the comparison of glaze formulations based on the amount of leachable metals.
• Supports product development and quality control.
• Helps to select glaze formulas for ceramic products intended for food contact. 

What Materials Can Be Tested Under ASTM C738? 

The ASTM C738 standard covers all glazed ceramic plates, cups, bowls, serving dishes, decorative ceramics, tiles, and food-contact glazes. Laboratories test all samples for lead and cadmium within predetermined limits using an acidic solution to ensure safe use. Analysts select representative glazed surface areas for the acetic acid extraction procedure. 

Why is ASTM C738 Important? 

The standard is important to public health as it provides confidence to consumers that food and beverages are safe from toxic exposure due to ceramic products, and it enables international trade by ensuring that these products comply with strict regulations. Its use on a regular basis reduces the risk of lead poisoning on a global level and guarantees the quality of ceramic products on the international market. Manufacturers use these measured extraction values to confirm that a glaze formulation meets food-contact safety requirements before products reach consumers. 

ASTM C738 Testing Process and Data Collection

Testing starts when the technician prepares the 4% acetic acid extraction solution and washes the surface of the glazed specimen. The technician then pours in the acid solution and allows it to leach for 24 hours at a controlled temperature between 20 and 24°C. The solution is then picked up by the technician after the extraction period for analysis. The amount of lead and cadmium in the extracted solution is determined in the atomic absorption spectrometer with the aid of the appropriate lamps for each element. Lastly, the analyst notes the amount of acid applied and the amount of lead and cadmium in parts per million.

Common Challenges and Troubleshooting

Testing is difficult because of issues in maintaining test conditions, such as temperature and acidity, and variability in glaze formulation. Troubleshooting is a recalibration of equipment, the correct preparation of extraction solutions, and verifying samples in standard solutions. Laboratories overcome these issues through the use of borosilicate glassware that can withstand harsh chemicals, by making sure that reagents are pure, and by regulating the temperature and duration of the extraction.  

• The laboratory reports the concentration of lead and cadmium in parts per million and the volume of acid used to extract the metals.
• The technician determines the type of ceramic product being tested (tableware, cookware, or another food contact product).
• The analyst documents the amount of metal extracted under the described conditions and compares it to the glaze being tested.
• The engineer considers factors such as the glaze composition, the firing conditions, and the firing surface when interpreting the results of the lead and cadmium extraction.
• Engineers use the measured extraction values to assist regulatory compliance and glaze formulation decisions for food-contact ceramics. 

Link to ASTM C738