If you have ever wondered "Can you put boiling water in mylar bags?" The short answer is yes, you can put boiling water in food-grade, thick Mylar bags, but not in thin or retail Mylar packaging. The bag must be heat-rated and designed for hot liquids. Never boil the bag itself or place it on a heat source.
This question comes up repeatedly with food storage, emergency preparation, and even cooking while camping.
What Mylar Bags Are Actually Made Of
Mylar bags consist of plastic and have lamination from the following layers:
- One layer of polyester film (aka Mylar).
- One aluminum foil layer for a barrier.
- One inner plastic layer, usually polyethylene, which makes contact with the food.
The inner layer is the most important to determine if the bag can withstand the heat adequately without softening, warping, or failing.
These same bags are commonly used for long-term food preservation, especially when storing dehydrated foods in Mylar bags.
Can Mylar Bags Handle Boiling Water?
Some Mylar bags may be able to endure boiling water, but not all of them are.
Boiling water has a temperature of about 212℉ or 100.0℃. Many mylar bags containing food grade material (with thick polyethylene lining) will withstand this high heat for a limited amount of time. These bags can be used for the following purposes:
- Dehydrated meals
- Food storage for backpacking and camping purposes
- Emergency food supplies or storage programs
- Sous vide cooking applications, when appropriate
Retail mylar packaging and other types of mylar packages that are thinner are not made to come into contact with boiling water. As such, they could become deformed, weaken their seals, or leak.
Because the inner layer comes into direct contact with food, it is important to understand whether Mylar bags are food safe before using them for hot liquids or food storage.
When It Is Safe to Use Boiling Water in Mylar Bags
Mylar bags can be used safely with boiling water once you make sure of the following conditions are correct:
- Make sure that the Mylar bag you're using is food grade.
- Make sure that the inner layer of the Mylar bag is heat rated polyethylene.
- Use a Mylar bag that is at least 5 mil thick (the thicker the better).
- Do not put the Mylar bag directly on the heat source where the boiling water will be used.
The water must be added to the Mylar bag after it has been poured inside, rather than by boiling the water inside the Mylar bag. This is why so many ready meal pouches state "add boiling water" as opposed to "boil in bag".
When You Should NOT Use Boiling Water in Mylar Bags
Don’t use boiling water in Mylar bags when:
- The bag is a thin promotional bag
- It doesn’t say it is food safe
- It has low quality heat seals
- You intend to expose the bag to prolonged heating
- You are unsure of what materials make the bag
The incorrect use of boiling water in a Mylar bag may cause the seal to fail, cause the plastic to become softened, and potentially add the risk of contaminating your food stored in the incorrect Mylar Bag.
Does the Aluminum Layer Matter With Heat?
When exposed to boiling temperatures, the outer layer of aluminum foil will not melt; however, it will not provide protection for an inner layer made of plastic from stress due to heat. Essentially, you should consider the aluminum foil to be a barrier instead of a form of armor. In the end, it will always be determined by the amount of heat transmitted through all the layers to the innermost layer.
Understanding the role of aluminum in Mylar packaging helps explain why heat tolerance depends more on the inner plastic layer than the foil barrier itself.
Best Practices for Using Hot Water With Mylar Bags
Here is some guidance about boiling water into a Mylar bag:
- Place it inside a bowl, cup, or similar container for support.
- When pouring it into the bag use a slow pouring technique
- Avoid overfilling the bag.
- Do not seal until after all the steam has been allowed to escape.
Following these tips will help reduce any leaks caused by condensation occurring at the seams of the mylar bag and minimize leakage overall.
Boiling Water vs Hot Water
Hot and boiling water are clearly different than one another. There are many Mylar bags that are not suitable for boiling but seem to work just fine as long as they are filled with hot water within the ranges of between 160°F and 180°F. An acceptable rehydration effect can be achieved by using instant foods or when moisture must be added and your materials are rehydrated within the limits of these temperatures.
FAQ: Boiling Water and Mylar Bags
Can you boil food inside a Mylar bag?
Yes, if they are food-grade and specifically made for boil-in-bag purposes.
Can Mylar bags melt?
Mylar film will not completely melt when exposed directly to boiling water, however, if there is enough heat applied to the inner plastic layer, this layer could melt or dehumanize (lost its original characteristics).
Are mylar bags safe when filled with hot liquid?
Yes, you can use food-grade, full-strength mylar bags for hot liquids if used properly & in accordance to what they are made for (i.e., heat resistance rating).
Can you store/cook using mylar bags while camping?
Yes, there are a lot of camping meals that require the use of a quality made mylar pouch (to use), and are very common for the purposes of cooking by "rehydrating" using boiling water.
Final Answer
So, can you put boiling water in Mylar bags? Yes, but only if the bag is food grade, thick, and designed for heat exposure. Using the wrong type of Mylar bag can lead to leaks, seal failure, or safety issues. When in doubt, assume retail Mylar bags are not heat safe unless stated otherwise.
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