7. Plastic Containers (Unless Marked “Dishwasher Safe”)
Plastic is tricky. Some plastics are fine, but many are not. The rule of thumb: if it’s cheap, thin, or old, keep it out.
The Science: Why it happens
The bottom rack of a dishwasher is very close to the heating element. The temperature here can exceed the melting point of many plastics. Even if they don’t melt, the heat causes the plastic to warp.
Furthermore, there is the issue of chemical leaching. High heat can cause chemicals like BPA or phthalates (in older plastics) to break down and leach into the plastic matrix, which can then transfer to your food later.
The Consequence
- Melting: You might open the dishwasher to find a plastic container melted onto the heating element or the rack. This is a fire hazard and ruins the machine.
- Warping: Lids will no longer fit containers. Containers will no longer sit flat.
- Clouding: Plastic becomes cloudy and scratched, making it hard to see what’s inside.
How to Clean It Instead
- Top Rack Only: If you must use the dishwasher, put plastics on the top rack, furthest away from the heating element.
- Hand Wash: The safest bet for Tupperware and takeout containers is a quick hand wash.
- Check the Symbol: Look for the “Dishwasher Safe” icon (usually a square with plates in it). If it’s not there, hand wash.
8. Copper Mugs and Pots
Copper is prized for its beauty and its excellent heat conductivity. It is often used for Moscow Mules or high-end cookware.
