by George Huang
Porcelain dinnerware is a common household item for many. But the risks to consumers when dinnerware is not tested during inspection before use are lesser known. A porcelain bowl can crack and break if heated too quickly. A casserole dish can shatter in your dishwasher during cleaning. And your favorite porcelain coffee mug advertised as “microwave-safe” can blow up in your microwave.
On-site tests for porcelain dinnerware are essential for product inspection of these items. Not only does testing help by verifying supplier claims like “microwave-safe”, but it also reveals the true performance and safety of the product.
Whether you’re an importer looking after your brand and your customers or an end user looking out for your safety, you’ll want to be familiar with these important tests for porcelain dinnerware:
- Thermal shock test for porcelain
The purpose of the thermal shock test is to determine the durability of the item after a sudden and rapid change in temperature. This ensures end consumers do not experience situations where an item cracks or shatters during normal use, which could be hazardous.
To carry out the thermal shock test on porcelain dinnerware:
- Place the item in a preheated oven for one hour.
- Wait for the surface temperature to reach a certain point according to the table below.
Small-Medium 180° +/- 5 356° +/- 41 Large-XL 160° +/- 5 320° +/- 41
- Hold the item under water for 10 seconds.3. Remove and immediately place in room temperature water (20°C +/- 5°C)
- Check to ensure there are no cracks in the body or in the glaze of the item. An item showing cracks or other damage fails this test.
- Stain resistance test for porcelain
Staining is a common problem in porcelain ware. A quality ceramic glaze on the exterior of the porcelain helps prevent staining. The stain resistance test will verify the porcelain’s ability to maintain color and cleanliness after contact with various food substances. This test is important because porcelain dinnerware will frequently come in contact with food.
Follow these steps for testing stain resistance:
- Apply a typical household food substance, such as tea, coffee, ketchup or soy sauce, to various surfaces of a porcelain item.
- Let the substance(s) sit on the porcelain for 2 hours undisturbed.
- Clean the porcelain with detergent.
- Check to ensure there are no visible changes compared with an untreated sample of the same item. If color has transferred to the surface of the porcelain and doesn’t wash away, that item has failed the test.
- Dishwasher resistance
Dishwasher resistance is one of the more practical tests for porcelain dinnerware that’s easy to perform. Sometimes the manufacturer of a particular item of porcelain dishware will add a claim to the product or packaging advertising that the item is “dishwasher-safe”. Using this very simple test you can assess any harmful effects caused by running the product through a dishwasher cycle.
To test porcelain for dishwasher resistance:
- Place the item in a dishwasher and wash using a normal cycle with dish detergent.
- After the cycle, check to ensure there are no visible changes when compared to an untreated item after the cycle. The item fails testing if any chips, cracks or other damage are found after washing.
- Water leakage check
Some porcelain items are made up of different components bound together during production. Material can leak through a dish if there are gaps between parts or glaze. The simplest test on this list, the water leakage check ensures that your items do not leak after storage over a period of time.
To check for water leakage:
- Fill the item with water.
- Wipe the outside of the item to make sure there is no moisture.
- Place the item on a piece of cardboard.
- Leave the item to sit for 2 hours undisturbed.
- Check if any water has leaked from the bottom of the item by examining the cardboard. Any sign of water leakage will fail this test.
- Microwave adaptability test
Many manufacturers make claims about dishes being “microwave-safe”, attesting that the item won’t break or melt in a microwave, release toxins or experience electrical arcing. When it comes to tests for porcelain dinnerware your main concern should be checking for electrical arcing.
This test will assess the item’s ability to keep its form and temperature in a microwave. Any electrical arcing indicates there are metal lusters or glazing present in the item like gold, silver or copper, and the item should not be microwaved. If an item deemed “microwave-safe” fails this test, there may be an issue with its production process.
Here’s how to carry out testing for microwave adaptability:
- Place the sample of dishware in water with a temperature of 20°C ± 3°C for 1 hour and then take it out and wipe the surface dry.
- Immediately place the sample in the center of the turn plate in a microwave and place two containers with 125ml ± 5ml of water in the opposite corners of the microwave. Make sure the two water containers do not touch the turn plate.
- Set the microwave to its highest power setting and then set the microwave timer to a duration (seconds) that equals 72,000J divided by its rated power output (wattage). Run the microwave.
- Exercise caution here: if any electric arcs appear during this part of test, stop the test and consider it failed.
- After heating in the microwave is finished, take the sample out and put it on a cool surface until it reaches room temperature.
- Check for cracks and any other visible defects, which will cause the item to fail testing if found.
On-site tests for porcelain dinnerware are such a vital component of pre-shipment inspection. You’re likely to find porcelain or ceramic dishes in the average American or European kitchen cupboard. And any issues or hazards found in dishes after sale can lead to expensive returns or recalls and damage to a brand’s reputation.
George Huang is a Client Manager at InTouch Manufacturing Services, a QC firm that performs product inspections and factory audits in Asia for clients in the US, EU and Australia.