Global Sources
Ready to import from China? Find verified suppliers on Global Sources.
Share / Recommend:

5 common defects in cast iron cookware

by George Huang 

Defects in Cast Iron Cookware Feature-small

Imagine being a chef in a busy, high-end French restaurant. The kitchen is an absolute boiler room. Rushing back and forth from stove to cutting board and from refrigerator to oven.

And suddenly, amidst the hectic chaos, you reach for a clean skillet and slice your hand on a spot of sharp metal–a common quality defect in cast iron. Blood quickly trickles from the wound. But you have no choice but to wrap your hand in a towel and continue through the busy dinner hour.

Most of us don’t work in a kitchen professionally. But have you ever taken a moment to appreciate the importance of quality tools and equipment for cooking? Substandard cookware can not only pose a hazard to the user, but to those consuming the food made as well. Cast iron cookware is an important example.

Cast iron cookware has seen a revival in recent years, following a rise in demand for nonstick Teflon and aluminum cookware in the late 20th century. It’s made by pouring molten metal alloy into individual molds and then left to harden.

Due to its unique properties and the production processes involved compared to other materials, cast iron cookware is vulnerable to more potential defects.


Let’s take a look at the most common defects in cast iron cookware.

1. Pinholes in cast iron

Almost always visible, pinholes are a common type of quality defect that can be found in cast iron cookware. A pinhole is the result of chemical reactions between oxidized metal (hydrogen and nitrogen) and carbon which causes bubbles to appear during the molding process.

Pinholes can affect the structural integrity of an item made of cast iron. But the greater concern with regard to cookware is that small pinholes can collect food particles that are difficult to remove by normal washing. These food particles can lead to the growth of unhealthy bacteria.

Some common causes for pinholes in cast iron include:

  • Excessive nitrogen in the molding sand with high moisture content
  • Hydrogen carriers introduce excess hydrogen to the melt (e.g. oily or rusty feedstock)
  • Slag (a byproduct of the smelting process) not skimmed completely

Defects in Cast Iron Cookware

To prevent the occurrence of pinholes in cast iron, the manufacturer may need to alter the feedstock to reduce hydrogen carriers that cause air bubbles. Shortening flow paths in the mold may also help by limiting the chances of oxidation that can cause air bubbles to form.

When found during product inspection, pinholes are typically classified as major or minor quality defects, depending on size and frequency.

2. Sharp flash

Flash is an excess of material that can appear as a protrusion at the edge of a component. Flash is among the more common defects in cast iron cookware and is also seen in injection molded products (related: Top 5 Injection Molding Defects to Avoid).

Flash is generally subtle and harmless on other products, like those made of rubber or plastic. But as is with all cast iron cookware, sharp material on any part of the pan may cause injury to consumers and is a huge liability. Sharp flash is generally considered a major or critical defect in cast iron cookware.


Sharp flash may be caused by:

  • Insufficient mold clamp force
  • Poorly fitting molding plates
  • Overfilling the mold during injection

Flash is not rare to see on post-production, pre-packaged cast iron cookware. But it’s important for your supplier to have a work station set up before the packaging stage for the purpose of grinding off any visible flash.

Increasing mold clamp force is one of the most common ways to prevent flash. Poorly fitting molding plates may require redesign, which is often a more expensive option for the factory.

3. Uneven enamel

Many cast iron cookware companies also manufacture enamel-coated cast iron. Enamel coated cookware is less likely to rust and cooks differently than traditional cast iron.

Enamel application is a complicated process involving numerous technical steps. It’s no surprise then that there are many defects that result from this process. This is a defect that occurs when an enamel is inconsistently applied to the raw cast iron cookware after it hardens. This defect is usually caused by:

  • Inadequate heating of cookware before application or
  • Manual error by the operator of the process

Defects in Cast Iron Cookware

Assuming a dry application process of the enamel, the percentage of defects found will highly correlate to skill of the operator. If you find areas on the finished cookware that are under or over coated, address this with the supplier. The factory should be able to adjust their technique to ensure a consistent coat.

4. Foreign material

Foreign material can be introduced to the cast iron during the enamel process and/or the molding process. The foreign material can appear in the enamel or even the raw cast iron body. Visible foreign material often has a negative effect on the item’s overall appearance. Foreign material can be added to the product via:

  • Poor base material used in cast iron
  • Insufficient cleaning of molds, or
  • Improper application of enamel

Defects in Cast Iron Cookware

While not cause for major concern, foreign embedded material cannot be removed through factory reworking. If the defect is seen in high numbers this may be reason enough for you to reject the order.

5. Rust in cast iron

Flash rusting occurs when a cast iron surface dries after a wet surface preparation. Flash rusting is very easy to spot as it changes the appearance of the cookware. This defect usually happens when:

  • Cast iron cookware is left to dry by air or
  • Stages of paint application have been contaminated

Small areas of flash rusting can be treated easily through chemical means by either the supplier or the end consumer. However, heavy flash rusting typically makes the item unsellable. So the presence of rust in the finished goods could be cause for you to reject the order.


With cast iron cookware’s recent surge in popularity, competition is fierce between brands. If you want to be a real player in the cast iron cookware market, you’ll want to manufacture a quality product that is both safe and appealing.

Whether you’re an importer or an aspiring chef, knowing these five defects in cast iron cookware will help you know what to look for in your next purchase.

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.


Want to know how to work with factories to produce your unique products?  Join the Smart China Sourcing Summit to learn sourcing best practices, April 17-19, 2016.  Co-located with Global Sources 3,000-booth trade show in Hong Kong.  Learn more at

Keep updated on sourcing best practices and the Summit.  Join the Smart China Sourcing Facebook group at

Add comment

Security code

Stay Connected

Get Import from China Headlines by E-mail

Attend the Global Sources Summit

  • For online & Amazon sellers
  • Interactive training led by sourcing & Amazon experts
  • Learn how to source profitably, avoid pitfalls
  • April 17 - 19, 2017 in Hong Kong
  • Co-located with Mobile Electronics and
    Gifts & Home shows

Learn More

Join the Smart China Sourcing Facebook Group
  • Connect with other buyers
  • Ask questions
  • Get advice from experts

Join Group

Join Global Sources on Facebook

Be our fan now for the latest sourcing news, practical sourcing guides and expert advice.

Follow Global Sources on Twitter

We'll keep you updated with tweets on sourcing news, trade resources & more.

Connector Manufacturers From Global Sources

Global Sources - New Products from DVI Connector Manufacturers