Most of us reach into the kitchen cupboard without giving a second thought to the symbols stamped into the bottom of a plastic container.
They’re small.
Easy to overlook.
But those tiny markings are far more than manufacturing details—they’re practical instructions that tell you how to use the container safely and help it last longer.
One of the easiest symbols to recognize is the fork and wine glass.
This mark indicates that the material is intended for food contact. While it doesn’t guarantee the container can withstand heat or freezing, it does mean the plastic has been manufactured for storing or serving food rather than for industrial or non-food purposes.
Another common symbol is the microwave icon, often shown as wavy lines.
This tells you the container is designed to tolerate microwave use under normal conditions. However, microwave-safe doesn’t necessarily mean the plastic remains cool or that it should be used indefinitely. Always avoid heating food beyond the manufacturer’s recommendations, and never microwave containers that are cracked, warped, or heavily scratched.
If you see a snowflake, the container is suitable for freezer storage.
Freezer-safe plastics are designed to remain durable at low temperatures, helping reduce the risk of cracking when frozen foods expand. Even so, leaving a little space at the top of the container allows liquids to expand safely as they freeze.
A dishwasher symbol indicates the container can be cleaned in a dishwasher.
Some markings specify whether the item belongs on the top rack only, where temperatures are generally lower. Following these recommendations helps prevent warping and extends the life of reusable containers.
Perhaps the most familiar marking is the recycling triangle with a number inside.
Many people assume this number indicates whether a plastic is “safe” or “unsafe,” but its primary purpose is to identify the type of plastic used for recycling. Even so, understanding these numbers can help you make informed choices about everyday use.
Some common examples include:
- #1 (PET or PETE): Commonly used for water bottles and soft drink containers. These are generally intended for single use, although many people reuse them. Repeated use and wear can make thorough cleaning more difficult.
- #2 (HDPE): A durable plastic frequently used for milk jugs, detergent bottles, and some reusable food containers.
- #4 (LDPE): Often found in squeezable bottles and flexible food packaging.
- #5 (PP or polypropylene): A popular choice for reusable food containers because it is durable and commonly designed to tolerate repeated use and, in many cases, microwave heating.
- #3 (PVC), #6 (PS or polystyrene), and some #7 plastics: These are generally less common for reusable food storage. Certain products in these categories may not be suitable for repeated heating, so it’s important to follow the manufacturer’s instructions rather than relying on the recycling number alone.
You may also notice the words “BPA-free.”
This simply means the product was manufactured without bisphenol A (BPA), a chemical once commonly used in some plastics. While many consumers prefer BPA-free products, the label doesn’t automatically mean a container is appropriate for every use or every temperature. Other aspects—such as microwave safety and the condition of the container—remain important.
One habit can make food storage much simpler:
Before using a plastic container, turn it over and check the markings.
If the symbols indicate it’s suitable for the way you plan to use it, you’re ready to go. If the markings have worn away, the container is badly scratched, warped, cracked, or you can’t identify what it’s made from, it’s often best to transfer your food to a container with clear, readable instructions.
These symbols aren’t there to decorate the bottom of your containers.
They’re there to help you use them correctly, extend their lifespan, and reduce unnecessary guesswork.
A quick glance takes only a few seconds, but it can help you choose the right container for the job—whether you’re freezing leftovers, reheating lunch, or storing tomorrow’s dinner. When it comes to food safety, a little information stamped into the plastic can go a long way toward making everyday choices simpler and more confident.
