Materials & Safety Symbols Guide

Once you understand a few symbols and materials, most “is it safe?” questions answer themselves. This section explains the codes stamped on your containers, the safety symbols on your cookware, and the material science behind the verdicts — so you can read any item, even one we haven’t listed yet.

Plastic recycling numbers, at a glance

The number inside the triangle on a plastic item tells you what it’s made of — and that largely determines how it behaves with heat. A quick orientation (always defer to the item’s own microwave-safe marking):

Code	Plastic	Heat note
#1 PET/PETE	Water & soda bottles	Single-use; not made for heating.
#2 HDPE	Milk jugs, tubs	Fairly heat-tolerant but not typically microwave-rated.
#5 PP	Yogurt tubs, food storage	The common microwave-safe plastic.
#6 PS	Styrofoam, disposable cups	Softens and can leach; avoid heating unless marked safe.
#7 Other	Mixed / newer plastics	Varies widely — check the item’s own marking.

Symbols worth knowing

• Microwave-safe: a dish with wavy lines, or the words “microwave safe.”
• Oven-safe: an oven outline, often with a maximum temperature.
• Dishwasher-safe: plates or glasses under water droplets, sometimes marked “top rack.”
• Freezer-safe: a snowflake symbol.

Guides in progress

Deeper explainers are on the way: a full plastic recycling-number reference, how to read tableware safety symbols, how to tell if a dish is oven safe when it has no marking, and a material melt-point reference. Browse the appliance hubs — Microwave, Oven, Air fryer, Dishwasher, Freezer — for the item verdicts, and tell us which guide to write next.