Why Are Some Ceramic Mugs Not Dishwasher Safe?

Ceramic mugs are a unique staple in many kitchens around the world. They come in various shapes, sizes, and designs, making them a popular choice for sipping your morning coffee or enjoying a cozy cup of tea.

While many ceramic mugs proudly boast their dishwasher-safe status, you may have noticed that some are labeled as "not dishwasher-safe." But why is this the case? 

In this article, we'll delve into the fascinating world of ceramics to understand why some ceramic mugs should avoid the dishwasher.

The Basics of Ceramic Mugs

Before we dive into the dishwasher problem, let's take a quick look at what ceramic mugs are made of. Ceramic mugs are typically crafted from clay, which is then fired at high temperatures to create a sturdy, durable material. The firing process is important because it transforms the clay into ceramics, which can withstand the daily rigors of holding hot beverages.

Ceramics can be divided into two main categories: porous and non-porous. The porosity of a ceramic item determines its ability to absorb liquids. Porous ceramics have small openings or gaps in their structure, allowing them to soak up moisture. Non-porous ceramics, on the other hand, have a more tightly packed system, making them resistant to liquid absorption.

Dishwashers and Their Impact on Ceramic Mugs

Dishwashers are great inventions that save us time and effort when cleaning dishes. However, they use powerful jets of hot water and strong detergents to remove grease, stains, and food particles. This cleaning process can be harsh on delicate items, including ceramic mugs.

The Dishwasher's Heat

One of the primary reasons why some ceramic mugs are not dishwasher safe is the intense heat generated during the dishwasher's wash cycle. This high temperature can cause ceramic mugs to expand slightly during the wash and contract as they cool down afterward.

This repeated expansion and contraction can stress the ceramic material, leading to cracks, chips, or even shattering in extreme cases. To avoid the risk of damaging your beloved ceramic mug, it's best to wash it by hand, where you can control the water temperature and avoid sudden temperature changes.

The Detergents and Chemicals

Another reason for avoiding the dishwasher with ceramic mugs is the strong detergents and chemicals used in the cleaning process. Dishwasher detergents contain harsh chemicals designed to break down tough food residues and grease. While these chemicals are effective at cleaning, they can also be abrasive to ceramic surfaces.

The prolonged exposure to these detergents may lead to the gradual deterioration of the glaze on your ceramic mug. The glaze is the shiny, protective layer that gives ceramics their smooth, polished appearance. When the glaze becomes damaged, it can make the mug more susceptible to staining, chipping, and cracking. By hand-washing your ceramic mugs, you can use gentler dish soap and avoid these potential issues.

Porosity Matters

As mentioned earlier, the porosity of ceramics plays a significant role in determining whether a mug is dishwasher safe. Porous ceramics, which have more open spaces in their structure, are prone to absorbing water and detergent. This absorption can lead to staining, odors, and even mold growth inside the mug. Porous ceramics are less likely to withstand the rigors of a dishwasher, making hand-washing the safer option.

Non-porous ceramics, on the other hand, have a tighter structure that resists liquid absorption. This makes them more suitable for dishwasher use. Many mass-produced ceramic mugs are glazed with a non-porous finish, making them dishwasher-safe. However, handcrafted or artisanal ceramic mugs often have unique glazes that may need to be more resilient, requiring gentler treatment.

Handle with Care


Ceramic mugs with delicate handles are particularly vulnerable in the dishwasher. The high-pressure water jets can apply force to these fragile areas, leading to handle breakage. Additionally, when mugs are placed close together in the dishwasher, they can collide during the wash cycle, potentially causing chips or cracks in the handles or the mug itself.

To preserve the integrity of your ceramic mug, it's best to hand-wash those with delicate handles. Gently scrubbing these areas with a soft sponge or brush can help extend the life of your favorite mug.

Hand-Washing Tips for Ceramic Mugs

Now that we've explored why some ceramic mugs are not dishwasher safe, let's look at some tips for proper hand-washing to ensure your cups remain in excellent condition:

  • Use mild dish soap: Opt for a gentle, mild dish soap to avoid damaging the glaze on your ceramic mug. 
  • Warm water: Use warm, not scalding, water to clean your mug. Extreme temperature changes can still harm ceramics.
  • Soft sponge or brush: Use a soft sponge or brush to scrub your mug, avoiding abrasive scouring pads or steel wool.
  • Handle with care: Pay extra attention to any delicate parts of your mug, such as handles or decorative elements.
  • Thorough rinsing: Ensure you rinse all soap residue from the mug, as this can lead to a soapy taste in your beverages. 
  • Air drying: Allow your mug to air dry rather than using a towel, which can leave lint or scratch the surface.

In the world of ceramic mugs, not all are created equal when it comes to dishwasher safety. Understanding the factors that contribute to a mug's vulnerability in the dishwasher, such as heat, detergents, porosity, and delicate handles, can help you preserve your favorite ceramic treasures.

By choosing to hand-wash your cherished ceramic mugs, you'll not only extend their lifespan but also ensure that they continue to bring joy to your daily coffee or tea ritual for years to come. So, the next time you reach for that "not dishwasher safe" mug, remember that extra care and attention can go a long way in preserving its beauty and functionality.