What Causes Ceramic Mugs To Crack?

So, you’ve noticed an unsightly crack in your favorite ceramic mug and are probably asking, “How did this happen?”. Fortunately, we have the answers for you. So, join us as we look into the causes of ceramic mug cracking.

There are several reasons why ceramic mugs can crack. The first reason for mugs cracking is due to the way they are manufactured. The mug can also crack due to being dropped or bumped, while another reason may be exposure to rapid temperature changes.

Once your mug has a crack, other factors need to be taken into consideration. Continue reading to find out what you can do with a cracked mug.

Why Do Ceramic Mugs Crack?

Ceramic mugs that have cracked can be a source of annoyance and frustration, even more so if it is your favorite mug. However, a cracked mug doesn’t always mean it has reached the end of its life and should be discarded. There are cracked mugs that are safer to use than others.

Cracks can occur as surface cracks or as deep structural cracks. If, for example, you notice cracks in the interior of your mug, it is more than likely a surface crack. To confirm this, sweep your finger across the interior of the mug. If there are no lumps or uneven surfaces, it is a surface crack.

These surface cracks are called crazing and result from the manufacturing process. More specifically, crazing happens due to incompatibility, or mismatch, between the clay and surface glaze. As a result, these two different materials expand and contract at different rates, causing cracks in the mug’s surface.

Therefore, it is not uncommon to see crazing after the first use of the mug. Do not fret, though. These cracks are unlikely to cause your mug to break completely. Structural cracks, on the other hand, are more severe cracks. Structural cracks can occur in one of two ways: dropping or bumping the mug or exposure to rapid temperature changes.

The former is evident and does not require any further explanation. However, the latter may need some additional explaining. Ceramic mugs are made to withstand high temperatures. However, this does not mean they are entirely resistant to the effects of temperature.

Thus, exposing your mug to high temperatures and rapid cooling can cause cracking. So, for instance, pouring hot liquids in the mug and immediately putting it in the fridge or deep freeze. Unfortunately, structural cracks indicate a more severe issue with the structure, so drinking out of the mug should best be avoided.

Is It Safe To Use A Cracked Ceramic Mug?

Whether or not it is safe to use a cracked mug is mainly determined by the type of crack that has infiltrated the mug. If the mug has a structural crack, do not use it. It would be best to discard these mugs at once or repurpose them. These cracks can fester and harbor bacteria which can be detrimental to your health.

An immunocompromised person can be even more vulnerable to the effects of this bacteria as well. Likewise, these mugs pose another safety risk. Due to the structural damage these mugs have, it has a high risk of falling apart or shattering while in use. Whether it is safe to use crazed mugs, on the other hand, is up for debate.

Some health departments do not allow dishes that have crazing due to safety concerns. And likewise, many people agree that mugs that have crazing pose a health risk. But, again, this is due to the bacteria and food that can seep into the cracks. Others argue that cracks are only surface-level and that proper washing is enough to kill bacteria.

It is believed that because the cracks are surface level, bacteria can not hide and fester as well as a structural crack. Also, it might be worthwhile to note that many people have used crazed pottery without experiencing any ill effects. But keep in mind, the majority does not mean everyone.

So whether you would want to keep your crazed dish is up to you. Before making your decision, you should consider that liquids will seep into the cracks.Over time, these liquids will stain those areas, resulting in an interesting pattern. If you do not like this aesthetic or are worried about bacteria, it is best to discard the mug.

Can You Fix A Cracked Ceramic Mug?

For the most part, you can fix a cracked ceramic mug. The first thing you need to decide is whether or not it is worthwhile to repair. Repairing mugs can take extra time, effort, and sometimes money. Additionally, if you are new  to repairing ceramics, you may just find yourself in a trial-and-error kind of process.

So, if the mug is just another mug, consider weighing your pros and cons. However, if your mug has sentimental value, and you’d rather keep it around for a few more years – that’s a different story.

The next step is to decide if you want to use the mug again for drinking or if you’d prefer to repurpose it, such as a pencil holder or decorative purposes. This is an important aspect to consider because some materials used to fix ceramics can be toxic and may not hold well against heat.

Cyanoacrylate glue, AKA Crazy glue or Superglue, Epoxy, and, believe it or not, milk, has been shown to help repair ceramic mugs. Additionally, if you do not trust your DIY skills or are too busy, you can take it to a ceramic studio and ask them to fix it for you.


Cracks in ceramic mugs can be due to a number of reasons, and sometimes these reasons are not your fault. However, there are ways to help prevent cracking by not dropping the mug or exposing it to rapid temperature changes. If cracks have occurred in the mug, determine if it is a structural crack or crazing. Mugs with structural cracks should never be used and are best discarded or repurposed.

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