So you came across these nifty coffee mug cake recipes that you can use in a microwave, but all you have is an oven. Can you put all coffee mug types in the oven? If not, which types are oven-safe, and at what temperatures are they safe?
Not all coffee mugs are oven-safe. Ceramic coffee mugs can go in the oven, as well as glass and bone china. Metal, stainless steel, and silicone mugs are oven-safe. Polypropylene and plastic mugs are microwaveable but not safe in a conventional oven.
Look for the manufacturer’s label to see if its product is oven-safe. In most cases, the uncertainty is because of the absence of appropriate labels and clear instructions. Keep reading to learn more about coffee mugs that are and aren’t oven-safe.
Is It Safe to Put a Mug in the Oven?
It might not always be safe to put a mug in the oven. Certain oven-safe materials might be okay, but coffee mugs often comprise more than just the base material, such as decorative elements, embellished handles and bases, glazing, and adhesives.
You must verify if these additional elements are oven-safe, too.
Take the example of coffee mugs made of metals or alloys. Stainless steel is oven-safe, like cast iron. However, if a stainless steel coffee mug has any plastic or wood, it is not safe in an oven.
Rubber, like those used as grips for pans, is usually oven-safe, but it suffers discoloration over time. Besides, not all types of rubber can endure the high temperatures in an oven.
Similarly, if a mug is a fusion of two or more materials, then you should verify whether each of those elements is oven-safe. The fusion method, sealant, or adhesive is another critical factor. If a coffee mug is painted or has some glaze that cannot tolerate high temperatures, it is not safe in an oven.
Coffee mugs may use different adhesives.
Epoxy has a heat tolerance range of 450 °F (232 °C) to 600 °F (316 °C) depending on how many parts of the resin are used and the curing method. Silicone adhesives tolerate 400 °F (204 °C) to 572 °F (300 °C).
Sodium silicate can endure up to 700 °F (371 °C).
Many coffee mugs have acrylic paint on them that begins to melt at around 266 °F (130 °C). Baking temperatures are usually between 300 °F and 570 °F (approx. 150 °C and 300 °C). If you intend to use a coffee mug for baking, an otherwise suitable material will become unsafe due to acrylic paint.
How Do You Know if a Mug Is Oven-Safe?
To know if a mug is oven safe, look for the relevant label on the product or package. The symbol used for this purpose is three or more vertical wavy lines inside a square or rectangle resembling an oven. Many companies mention “Oven Safe” on the label.
If you don’t find the relevant manufacturer’s label or other explicit declaration, it is better to conclude that you cannot use the mug in an oven. You may delve into the materials and the other elements of the mug, but it is safer not to experiment.
Oven-Safe Coffee Mugs
When you want to bake small dessert portions, what mug should you choose? There are five oven-safe materials used to make coffee mugs. Let’s take a look at these materials.
Ceramics
Three types of ceramics are commonly used to make coffee mugs:
- Earthenware
- Stoneware
- Porcelain
Earthenware is the weakest among the three, but it’s sturdy enough to endure the high temperatures in an oven. All ceramics undergo multiple rounds of firing or burning during the manufacturing process.
The first transformation of clay into a ceramic involves firing at a temperature of up to 1945 °F (1063 °C).
The temperatures that each type can handle are as follows:
- Earthenware can handle 1945 °F (1063 °C).
- Stoneware can withstand 2382 °F (1306 °C).
- Porcelain can endure more than 2300 °F (1260 °C).
Hence, all ceramics have exceptional heat resistance. However, there is a caveat.
Ceramics used for cookware and bakeware are thicker, stronger, and heavier than the relatively lightweight and slender earthenware, stoneware, or porcelain used for coffee mugs. You will feel and know the difference instantly if you are familiar with ceramic ovenware.
Borosilicate Glass
Ordinary glass tends to crack upon sudden exposure to high heat or significant temperature fluctuation, a phenomenon known as thermal shock.
Regular glass can fracture under temperature fluctuations ranging between 176 °F and 212 °F (80 °C and 100 °C). The low heat resistance is why glassware is typically not used as cooking utensils.
However, borosilicate glass can withstand temperature fluctuations of around 297 °F (165 °C). Quartz glass can endure a temperature fluctuation of as much as 1832 °F (1000 °C). If you have a coffee mug made from borosilicate or quartz glass, then you can safely use it in an oven.
Bone China
Bone china is a type of ceramic.
Unlike earthenware and stoneware that are made from clay, bone china includes bone ash and other materials. Many companies and people refer to bone china as a type of porcelain, but the two aren’t identical.
Likewise, fine china is different as it doesn’t contain bone ash.
Bone china is subjected to very high heat during manufacturing, although just short of how porcelain is fired. The manufacturing process itself lends exceptional heat resistance to bone china.
Unless a coffee mug comprises additional materials, bone china is oven-safe.
However, like ceramic coffee mugs, the bone china used for a particular mug design or style may be slender and thus fragile to an extent.
The heat resistance is proportionate to the hardness and tensile strength of bone china.
Also, you should factor in the increasing pressure thrust on these materials if you are baking or cooking. Thinner walls of coffee mugs may fail to endure the expansion of foods and increasing pressure, which means that they may break or shatter in an oven.
Metal & Stainless Steel
Metal and stainless steel are hard and durable materials and are perfect for thermoses and sturdy coffee mugs you could carry with you. Both metal and stainless steel are oven-safe unless any material is used for embellishment that cannot tolerate high temperatures.
However, neither metal nor stainless steel is microwave-safe. Metal reflects microwaves, so you cannot heat or cook anything in them. They won’t shatter or blow up in a microwave oven, though.
Silicone
Silicone coffee mugs are oven-safe. You may also use them in a microwave. Silicone lids are safe, too, for both conventional ovens and microwaves. However, you must still check if the silicone mugs have any embellishment, paint, or other materials that render them unsafe in an oven.
Oven-Unsafe Coffee Mugs
There are four materials used to make coffee mugs that are unsafe in an oven. Let’s take a quick look at these.
Paper
Coffee cups made from paper aren’t oven-safe.
While paper can’t endure high temperatures, the glue and plastic films used in such cups are toxic when subjected to oven or microwave heat. Most paper cups are disposable, and you shouldn’t reuse them unless a particular variety is washable.
Plastics
Government regulators and industries use resin id codes to classify plastics. Recyclability and other properties, such as microwaveable or not, are based on the code.
There are 7 resin id codes for all commonly used plastics:
- Polyethylene terephthalate (PET)
- High-density polyethylene (HDPE)
- Polyvinyl chloride (PVC)
- Low-density polyethylene (LDPE)
- Polypropylene (PP)
- Polystyrene (PS)
- Other plastics
No plastic is oven-safe. Propylene (PP) is microwave-safe, as well as HDPE and LDPE with resin id codes 2 and 4, respectively.
PET and PC with codes 1 and 7 are not ideal for microwave ovens. PVC and PS with id codes 3 and 6 are unsuitable for microwaves. Resin code 7 is for miscellaneous plastics. Any plastic in this category is neither oven-safe nor microwaveable.
Like paper, plastic coffee cups are also meant to be disposable. Even if a hard plastic doesn’t readily melt in a microwave, it can exude toxic fumes that will not only make a food or drink inedible but shall also be harmful upon inhalation.
Plastic bags used in baking ovens have code 7. Such plastic is microwave-safe. But any plastic in this category that doesn’t explicitly say that it’s oven-safe should not be presumed to be so.
Plastics with code 7 may be a bio-plastic, a new kind of plastic, or a combination of different materials that haven’t been clearly defined. A plastic may contain polycarbonate, or there could be a presence of Bisphenol-A (BPA). Both are harmful.
Melamine
Melamine is widely used to make utensils, dinnerware, and other kitchen essentials.
The material is a nitrogen-based hard plastic and durable for many applications. However, it’s not an ideal cooking vessel. Melamine isn’t oven-safe. Also, you shouldn’t microwave melamine mugs or cups until you receive more clarity from the FDA.
Polystyrene Foam (Styrofoam)
Polystyrene foam is cheap plastic. Styrofoam shot to fame due to its ability to keep coffee warm.
In reality, polystyrene foam is a toxic substance, and you shouldn’t use it to store or carry hot and acidic foods. Not only is polystyrene foam oven-unsafe, whether or not you may microwave coffee mugs made of the material is also a grey area.
Polystyrene is considered microwave-safe if the product label or package says so.
Coffee mugs made from polystyrene are usually disposable. While the material may endure some heat it’s exposed to in the microwave, substances used in the manufacturing may seep into the drink or food, and the risk is grave.
Conclusion
Safety is paramount. Always verify if the material is oven-safe. Also, not every oven-safe coffee mug can endure high temperatures with equal ease. Choose appropriate temperature settings depending on the material you have.
