Are Mason Jars Heat Proof?

heat proof mason jars
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Mason jars are most well-known for home canning and food preservation. However, they have become a staple for DIY projects, crafts, decor, and more.

With all their uses, an important question comes up – are mason jars heat proof? Can these glass jars withstand high temperatures when canning, microwaving, or storing hot liquids? 

Let’s take a closer look at how to use mason jars safely with heat.

Key Takeaways

  • Mason jars can tolerate heat up to approximately 392°F (200°C) under gradual heating conditions but are prone to thermal shock with sudden temperature changes.
  • Newer mason jars made from tempered glass are generally microwave-safe, but precautions should be taken to avoid sudden temperature changes. 
  • Mason jars are not safe for use in ovens due to their susceptibility to thermal shock.
  • Hot liquids can be added to mason jars if the jar is preheated with warm water to minimize the risk of thermal shock.
  • Mason jars are not suitable for high-heat oven baking but can be used for sous vide cooking, no-cook meals, and as storage containers.
  • Hot mason jars should not be placed directly in the fridge to avoid glass cracking or shattering from the temperature change.
glass mason jars

Are Mason Jars Heat Resistant?

Mason jars are great for storage, but they have limitations when it comes to heat. While technically they can withstand some heat, it’s important to understand two key factors: temperature tolerance and thermal shock resistance.

Regular mason jars are made from soda-lime glass, which can handle temperatures up to around 392°F (200°C). However, this is only under ideal conditions with slow and gradual heating.

The bigger concern is thermal shock resistance. Mason jars don’t handle sudden temperature changes well. Placing a hot jar directly into cold water can cause the glass to crack or even shatter.

Also, be aware that the rubber seal in the lid, while it can handle heat to a certain extent, can degrade at high temperatures. This degradation can compromise the seal’s ability to form a tight closure over time, potentially leading to leaks or spoilage.

Can You Microwave Mason Jars?

a mason jar inside a microwave

Newer Mason jars are generally made from tempered glass, which is designed to withstand microwave heat.

If the jar is relatively new, or bears a symbol indicating that it is microwave-safe, then it is typically okay to use in the microwave.

However, when microwaving a mason jar, you should exercise the same care as with any glassware in the microwave:

  • Avoid extreme temperature changes: Glass, even tempered glass, can break if subjected to sudden extreme changes in temperature. Do not move a jar from the refrigerator or freezer directly into the microwave. Allow it to come to room temperature first. Similarly, avoid placing a hot jar on a cold surface or filling it with cold liquid immediately after microwaving.
  • Loosen the lid or remove it completely: While metal lids should never be placed in the microwave, if your jar has a microwave-safe plastic lid, loosen it or remove it entirely to allow steam to escape and prevent pressure buildup. Remember, metal in the microwave can cause sparks and fires.
  • Check for cracks and chips: Before microwaving, inspect the Mason jar for any signs of damage, such as cracks, chips, or scratches. Damage can compromise the jar’s integrity and lead to breakage when heated.
  • Consider the contents: The density and water content of the food being heated can affect how it heats in the microwave. Dense foods or those with uneven textures may heat unevenly, leading to hot spots.
  • Heating time: Start with shorter heating times and adjust as necessary. Overheating can cause food to become too hot, making the jar difficult to handle, or worse, cause the contents to boil over or explode.
  • Handle with care: Use oven mitts or a towel to handle the jar after microwaving, as it can be very hot. Allow the jar to cool down a bit before consuming its contents directly.

Can You Heat Mason Jars in the Oven?

A shattered glass mason jar inside an oven

Since mason jars are made from soda-lime glass, they are susceptible to thermal shock. This means rapid changes in temperature can cause the glass to crack or even shatter. The intense heat of an oven can easily create this kind of shock, making them unsafe for oven use.

Can You Put Hot Drinks in Mason Jars?

Putting hot drinks in mason jars is possible, but you need to take a few safety precautions. When canning or storing hot soups, sauces, or beverages in mason jars, it’s important to allow the contents to cool properly before sealing the jar. 

Adding boiling hot liquids to a room temperature glass jar can create thermal shock, which can cause the glass to expand too quickly and possibly crack. 

To avoid this, preheat your mason jar with warm water before pouring in the hot liquid. This helps the glass adjust to the temperature gradually.

Keep in mind that while mason jars can handle boiling water, it’s generally recommended to use them for liquids close to boiling or even slightly cooler.

If the hot liquid has been simmering for a long time, letting it cool slightly before transferring it to the jar is a safe practice.

Is it Safe to Pour Boiling Water in a Mason Jar?

Pouring boiling water directly into glass mason jars can be risky business. The intense heat of water can deliver thermal shock to the jar and cause it to crack or shatter.  

This happens because of the rapid temperature change. Mason jars are designed to withstand high heats when gradually warmed in an oven or pot of water. But dumping boiling water directly into a room temperature glass jar creates a sudden, drastic jump in temperature that the glass cannot handle.

The thermal shock can create weak spots or micro-fractures in the glass that may cause it to break immediately or later down the road.

Instead of pouring boiling water straight from a kettle or pot, it’s safer to use one of these alternatives:

  • Place the jar in a pot of water and bring to a boil, letting the glass warm gradually. 
  • Set the jar on a hot pad or trivet and pour the boiling water. The pad helps prevent severe temperature spikes.

Can You Cook in a Mason Jar?

Vegetable soup in a glass mason jar

Mason jars are a handy kitchen tool, yes, but when it comes to cooking, there are some things to keep in mind. For instance, high-heat oven baking is a no-go because regular mason jars aren’t made of heat-resistant glass and could shatter.

However, mason jars excel in other areas. They’re perfect for sous vide cooking, where food gently cooks in a sealed jar submerged in a precisely controlled water bath. 

And for no-cook meals like salads in a jar or overnight oats, mason jars are fantastic for layering and storing ingredients for a grab-and-go meal prep option. 

Can You Put Hot Mason Jars in the Fridge?

It’s recommended that you avoid placing hot mason jars directly in the fridge. The sudden temperature change can cause the glass to crack or shatter.

To safely store your food, let your filled mason jars cool completely at room temperature before placing them in the fridge. This will prevent the jars from breaking. 

Tips for Using Mason Jars Safely with Heat

  • Before adding hot liquids, preheat your mason jars with warm water. This helps the glass adjust to the temperature change gradually, minimizing thermal shock.
  • Don’t place hot jars directly on cold surfaces like granite countertops. The sudden temperature difference can cause cracks. Use a trivet, hot pad, or wooden cutting board as a buffer when placing hot jars down.
  • When using mason jars for storing or holding hot beverages, ensure the lids are secure but not over-tightened. Over-tightening can trap heat and pressure, leading to breakage.
  • Always inspect your mason jars for cracks, chips, or other imperfections before using them with heat. Damaged jars are more susceptible to breaking under thermal stress. Discard any jars with visible flaws.
  • Wash your mason jars with warm, soapy water after each use. Let them air dry completely before storing or using them again. This helps prevent any residual moisture from contributing to thermal shock during future heating.
  • Metal lids can spark and damage the microwave. Additionally, the uneven heating distribution in microwaves can cause the glass to crack.
  • Don’t fill mason jars to the brim with boiling liquids. Leave some headspace at the top to allow for expansion as the contents heat up.
  • When simmering liquids on the stovetop with mason jars, gradually increase the heat to avoid sudden temperature changes.

Wrapping Up

Mason jars, with their charm and practicality, have secured a place in our kitchens and hearts.

Whether it’s for canning summer’s bounty, crafting the perfect overnight oatmeal, or even sous vide cooking, understanding their capabilities and limits with heat is key to both creative exploits and everyday uses.

By respecting their thermal tolerance and applying best practices, you can harness the full potential of mason jars in your culinary adventures and beyond.

Check out our blog post on Creative Mason Jar Decoration Ideas for more inspiration on how to use mason jars in your home. 



  • Dacia Flowers

    Dacia Flowers is a graduate of the University of Nevada, Las Vegas (UNLV) with a major in Cultural Anthropology. Since graduating in 2019, she has expanded her expertise and applied her anthropological background in the practical domain. As the Administration Manager at CMJJ Gourmet since August 2022, Dacia handles crucial day-to-day operations, ensuring the warehouse's optimal functionality, timely delivery of orders, and managing invoices. Her commitment to excellence and in-depth understanding of organizational dynamics stem not just from her academic prowess but also her personal passion. Beyond her professional responsibilities, Dacia has a keen interest in reading, loves to travel, and stays active through regular exercise.

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