Have you ever wanted to reheat some hot chocolate or a cup of cold coffee, but you don’t have a microwave? Or maybe you’re craving soup and there isn’t a single bowl in sight? No, wait—you have a sweet tooth craving and all the ingredients for a mug cake, but again, no microwave to make a mug cake in? Turning to using your oven seems like a reasonable idea.
This leads to the question: can you put a mug in the oven? What happens if you’re using your favorite coffee mug—are you going to risk ruining it forever? Don’t worry! You and your prized mug should be fine … if it’s made out of the right thing, that is.
Most mugs come with some kind of oven-safe label or inscription on the bottom that will give you a heads up as to whether it is an oven-safe cup or not. Plastic mugs and paper mugs are not oven-safe, but stoneware mugs are fine.
If your mug happens to fall into the right category, as most mugs made by coffee mug manufacturers of a certain quality are, it’ll survive just fine. In our guide, we’ll lead you through the process of determining which mug to use for your next treat made in the oven!
- Are Mugs Safe to Put in to Oven?
- Is Microwave-safe the Same as Oven-safe?
- How Long Can You Put a Mug in the Oven?
- How Can You Tell if a Mug is Oven Safe?
- What Temperature Should Coffee Cups Be?
- What Temperature Does Ceramic Crack?
- How to Avoid Thermal Shock
- A Few More Things to Avoid
Are Mugs Safe to Put in to Oven?
The answer is—it depends!
A mug is a very general term since a mug can actually be made out of any number of things. Before you try putting a mug in the oven, you should first determine what the mug you’re using is made from and if that is an oven-safe material.
|Bon China Mug||No|
|Glass Mug||No / Yes|
Here are some common types of coffee mugs based on what the mug’s material is. Check them out below to make sure yours can withstand a trip to the oven.
1. Plastic Mugs
We’re going to start off with the easiest version of a mug to address. The answer is a resounding no. Do not put plastic cups in your oven.
While some of the mugs made out of plastic are microwave-safe, plastic mugs in the oven will melt. This could not only damage the oven itself but could also release fumes from the plastic that could be toxic to breathe. Steer clear of ever putting plastic mugs in the oven.
2. Paper Mugs
Paper cups may also melt if they have a wax lining on the inside, but it is more likely that they will burn when introduced to an extreme temperature, given their low flash point.
This is another one to avoid at all costs. You shouldn’t use them in the microwave either—odds are that the paper will melt or become disfigured, and the entire contents of the mug will spill all over your microwave.
3. Porcelain Ceramic Mugs
Some porcelain mugs may be oven-safe, but you may not want to take the risk. A porcelain mug is usually thin and that makes it more of a risk of being damaged by thermal shock. Not all porcelain mugs are at risk of this, but you may not know until it’s too late.
Porcelain is tender and frail, but often quite expensive and beautiful. It’s best to ensure that you don’t damage it rather than risk it.
How to Tell if a Mug is Porcelain?
Porcelain mugs can be identified by their thinness. Imagine a dainty, delicate teacup in a set your grandmother might have had, kept far away from the sticky, clumsy hands of children; those types of mugs are most likely to be porcelain coffee mugs.
4. Bone China Mugs
Bone china mugs are known for their delicate appearance, which might make them fantastic collector items and good shelf decoration … but, unfortunately, it does not make them safe to go in the oven.
In addition to their daintiness, the paint they’re often decorated with may also not react well to extreme heat. These bone china coffee mugs may be better left as beautiful art on the shelf as opposed to coffee mugs you’re using in an oven.
5. Glass Mugs that are Oven-safe
A glass mug is in that frustrating category of sometimes yes, it can go in the oven, and sometimes no, it’s not an oven-safe mug. It is going to generally be safest to assume that if your glass mug does not have an oven-safe symbol clearly visible on it, you shouldn’t risk it.
However, some glass mugs are specifically designed to withstand high oven temperatures. These are made with a type of material called borosilicate glass, or tempered glass, which is heat resistant. Such mugs are safe to put in the oven. They will not crack even under very high heat.
6. Glass Mugs that are not Oven-safe
If your glass mug is made of soda-lime glass, you have to be warned that those are not oven-safe coffee mugs. Because they are not made to be resistant to very high temperatures, a glass mug made of that type of glass will crack in a conventional oven.
A glass mug that cracks, or even explodes, in your oven could be disastrous to all of your future endeavors. If you aren’t sure what kind of glass mug you have, do not put that mug in the oven. Before you take the plunge, make sure that you check if your mug is made out of tempered glass or not.
7. Stoneware Ceramic Mugs
Stoneware mugs are clay pottery items that are made to withstand high temperatures—that should come not surprise! After all, stoneware mugs go through the process of being baked into their final form. This leaves them extremely well suited to being put in a microwave or an oven!
You can go ahead and assume a stoneware mug is going to be an oven-safe coffee mug, unless it has some kind of added decoration that makes it no longer so. The structure of the mug will remain intact, but the decoration might melt, depending on the material that was used.
The sealant plays a part in that, too—unsealed designs are not safe, but a sealed piece of decoration should be fine. You can tell whether it’s been sealed by examining the surface. A shiny, polished surface over the decoration suggests the presence of a sealant. If it’s matte or just the same as the rest of the mug, it could be in danger.
How to Tell if a Mug is Stoneware?
A stoneware mug is stronger and more non-porous than an earthenware one. It will easily go into the oven and come out just fine, because it is fired at a higher temperature and is more durable as a result. These are the only type of ceramic mugs that you should consider oven-safe mugs.
8. Earthenware Ceramic Mugs
An earthenware mug is made in a similar way to stoneware mugs but is not considered safe for oven use. They are heavy and durable for many uses in the kitchen, but not made to withstand the extreme heat they’d be exposed to if they were put in the oven.
The main difference between stoneware mugs and earthenware mugs is the durability of the finished product. Earthenware is softer and more porous, while stoneware—like its namesake—has a harder finish due to being fired at a higher temperature.
If you do have earthenware mugs, you should keep an eye out for chipping. You can identify a chip in the material by the sight of the plain white clay that will be exposed.
Earthenware mugs are also often decorated or painted, which would not react well to the heat of an oven. One way or another, this one is a no for oven use.
How To Tell if a Mug is Earthenware?
While they both have a very rustic aesthetic, earthenware mugs are more soft and porous. They are made of red clay or terracotta and are fired at a lower range of temperatures. This is what makes them not safe mugs in the oven. They’re also more prone to developing chips.
9. Camping Mug
A camping mug is generally made from pure metal and is therefore designed to handle an open flame or the heat you’d find in an oven. You can keep these in the oven all you like and they won’t mind a bit. The worst thing that can happen is some discoloration.
10. Metal Mugs
While all camping mugs are metal and all camping mugs are oven safe, not all metal mugs are oven-safe. If you find that a little hard to wrap your head around, don’t worry—we’re here to explain.
The important thing to remember is that if your metal mug has a non-stick finish or any plastic elements on it, it should never be put inside the oven. A pure metal cup, on the other hand, can be safely put in the oven.
This type of mug is yet another tricky option. It is not a complete no … but also not a complete yes. You’ll have to do your homework and study the specific mug in question to know.
11. Mugs with Decorations
It may be tempting, but resist! Mugs with decorations, no matter what the actual mug is made out of, should not be put in the oven.
The only exception is if you can absolutely guarantee that the other materials the decorations are made of were also designed to withstand temperatures that can include extreme heat. If you can’t be sure of that, do not place these mugs in the oven.
There is a very high chance that these decorations will melt or release toxins into whatever food or drink item you are reheating. You don’t want to end up with a bad case of food poisoning just because you wanted to use your favorite mug.
Is Microwave-safe the Same as Oven-safe?
Most coffee mugs will be made to be microwave safe, but not every microwave-safe mug can go into the oven. Some coffee mugs come with a helpful oven-safe symbol telling you that they can in fact go into the oven, but for some, you’ll have to rely on educating yourself—just like this article will do.
Unfortunately, many manufacturers won’t tell you straight up if your mug can go into the oven or not. You’ll have to figure that out for yourself based on the material used in its creation.
How Long Can You Put a Mug in the Oven?
How long your mug can stay in an oven, safe from cracking, will depend on what it is made out of, and how hot the oven is.
As a general rule of thumb, even if your mug is considered oven-safe, you still don’t want to keep it in there for too long. Keep the temperatures fairly low and check back on your mug every so often. If something seems off, take it out immediately.
How Can You Tell if a Mug is Oven Safe?
There are a few ways to determine if the coffee mug you’re wanting to use is oven safe.
Look For the Symbol on Oven-safe Coffee Mugs
Many times, an oven-safe coffee mug will have an indicator imprinted on the bottom of the mug. Coffee mug manufacturers print this so that you will know clearly if it is safe to put that mug in the oven. The coffee mug will either say the words ‘oven safe’ in clear print that you should be able to read, or it will have a symbol on it.
While every symbol is not identical, there are generally accepted visuals meant to tell you something is an oven-safe mug at a glance. The symbol for oven-safe should be a rectangle with oven knobs on it. If you see that, you’ll know those are mugs oven safe for you to use.
Do not confuse this with the symbol that tells you something is microwave safe, which is also a rectangle with knobs at the top. The microwave oven safe symbol generally has circles or wavy lines signifying the microwave signals used to heat food or coffee cups in them.
Check with the Manufacturer of the Coffee Mug
If you know where the coffee mug came from but do not know if the mug is oven-safe, you can check directly with the manufacturer to see if it is made of an oven-safe material. Search for the company name online and see what comes up—most will have some contact information listed right there in the search.
Determine the Type of Ceramic Coffee Mugs
If your mug is ceramic or handmade, you will need to find out what type of ceramic coffee mug it is. As covered earlier in this article, the three types of ceramic are porcelain, earthenware, and stoneware. The difference between these three is the finish and the time they bake in the oven.
It is important to know and not just guess. While all three of these may go in the oven and appear fine at the first glance, the coffee mugs will crack if the temperature change is too much and too abrupt. The same applies if the hot mug is too thin to be heat resistant to very high temperatures.
What Temperature Should Coffee Cups Be?
The perfect temperature to put your coffee cups in the oven is 140°F.
This will avoid the coffee itself actually burning or taking on bitter notes, and your mug will continue to keep the coffee warm even once removed from the heat source.
Of course, this temperature only applies to mugs that were oven-safe to begin with.
What Temperature Does Ceramic Crack?
Even oven-safe mugs made of ceramic can crack.
The biggest danger when heating a ceramic coffee mug is a thermal shock. This is when a cold mug is introduced to sudden heat. Ceramic construction on a mass retailer level, while still durable enough for everyday use, is also only meant to withstand a maximum temperature of 200°F.
What Happens if Your Ceramic Mug Cracks in the Oven?
Even if your ceramic mug is oven safe and does not fully crack under thermal shock, there may be a danger of fine hairline cracks in the glazing. This can be dangerous because bacteria can get into those cracks. It’s also very difficult to clean out.
To avoid this risk, do not consider any mugs with cracks in them to be oven-safe mugs even if the crack does not extend all the way through. Putting such a mug in the oven would only make things worse.
How to Avoid Thermal Shock
Thermal shock will ruin your coffee mug, but it is possible to heat a mug made out of oven-safe material without risking the cracks.
In order to prevent your oven-safe mug from still cracking due to thermal shock, you should put your mug in the oven as the oven preheats.
The process of slowly heating it is important because it stops the temperature disparities that lead to cracks.
Allow to Cool
When you’re done making your mug cake or whatever yummy treat you’re heating up in the mug, you should also not remove hot mugs immediately. The mug should stay in the oven until it has cooled, again to avoid steep temperature differences.
A Few More Things to Avoid
- Never put cold water in a coffee mug that is still hot.
- Do not run hot cups under cold water.
- Do not pour boiling water into a cold mug.
- Plastic and paper mugs do not go into the oven.
The key thing to remember when trying to decide about a coffee mug’s oven-safe status is that it depends on what kind of coffee mug you want to use! Remember that higher quality means that there’s a higher chance the mug is oven-safe, but it’s not a guarantee.
Some mugs, like a plastic mug, bone china, ceramics like a porcelain mug, and earthenware should not go in the oven. Others, like stoneware and tempered glass, are perfectly suitable mugs in the oven. Using this kind of mug in the oven that is safe to use might cost you a little more. On the other hand, if you really want to heat your coffee in an oven, it might just be worth a few pennies more to get your wish.
So enjoy that mug cake or reheated cup of coffee… but do so safely, and remember that if you aren’t sure what your mug is made out of, you should probably just stick to sipping your morning brew cold—lest you lose your favorite cup!