My Roommate Tried to Heat Up Tupperware in My Brand New Slow Cooker—Here’s What Happened

I got my first slow cooker last week. Today, my roommate melted Tupperware inside it.

Let me paint you a picture.

It was a Tuesday. I came home from work, excited to finally use my new 6-quart Crock-Pot for the first time. I’d been waiting all week to make a proper pot roast. The box was still sitting on the counter. The ceramic insert was still spotless.

I walked into the kitchen and immediately smelled burning plastic.

My roommate was standing at the counter, scrolling through her phone, totally unbothered. The slow cooker was on. The lid was on. And inside, jammed crookedly into the pot like a shipwreck, was a bright blue plastic Tupperware container.

Full of leftover pasta.

She looked up. “Oh hey. I couldn’t find a pot so I just put this in here to heat up. Is that okay?”

No. No, it was not okay.

Here’s the thing: I genuinely thought this was common knowledge. You don’t put a slow cooker on with an empty ceramic insert. You don’t put frozen raw chicken in and walk away for 10 hours. And you absolutely, positively do not put plastic containers inside a dry, heating slow cooker.

But apparently, not everyone got that memo.

So, in the spirit of education and public service, here is everything I’ve learned in the past 48 hours about what you can and cannot put in a slow cooker—so your roommate (or you, no judgment) doesn’t make the same mistake.

What Actually Happens When You Put Tupperware in a Slow Cooker

Slow cookers work by heating the ceramic pot from the bottom and sides, slowly and evenly. When you put an empty plastic container inside and turn it on, here’s what happens:

The ceramic gets hot.
The air inside gets hot.
The plastic gets hot.
The plastic melts.
You now have a $50 slow cooker permanently infused with the ghost of last Tuesday’s ziti.

In my case, the bottom of the container fused slightly to the ceramic. The lid had heat-warped into a gentle oval shape. And the smell—oh, the smell—lingered for two days, three vinegar washes, and one very skeptical cat.

Why People Make This Mistake

Look, I’m not here to roast my roommate (though I did, gently, over dinner). I get it. Slow cookers are deceptively simple. They look like magic pods that just make food hot. If you’ve never used one, you might think: “It’s just a heating element. What’s the difference between this and a stovetop?”

The difference is everything.

A stovetop heats a pot from below. A slow cooker heats the pot itself—all sides, all at once. There’s no buffer. No water bath. No air gap. If you put something non-food inside, it becomes part of the cooking process.

And plastic was never meant to be part of that process.

What You Can Put in a Slow Cooker (Besides Food)

Here’s the good news: once you know the rules, slow cookers are incredibly forgiving.

Yes:

Food (obviously)
Liquid (broth, water, sauce)
Parchment paper (for lining, if you want easy cleanup)
A slow cooker liner (specifically designed for this purpose)
Aluminum foil (crumbled into balls to lift meat out of liquid, or as a lid seal)

No:

Plastic containers (even “microwave-safe” ones—slow cookers get hotter than microwaves in a different way)
Empty ceramic inserts
Frozen blocks of food without liquid (thermal shock can crack the pot)
Your roommate’s questionable judgment

How to Fix a Melted Plastic Disaster

If you’re reading this because you or someone you live with has already made this mistake, here’s how to salvage your slow cooker:

Unplug immediately. Do not let it continue heating.
Let it cool completely. Do not try to pry hot plastic off.
Remove the plastic carefully. If it’s stuck, put ice cubes in the plastic container—cold makes it brittle and easier to break away.
Wash with vinegar and baking soda. The smell is the real enemy. A paste of baking soda left overnight can help.
If the smell persists, try leaving the ceramic insert in the sun for a day. UV rays and fresh air do wonders.

In extreme cases, you may need to replace the ceramic insert. Some brands sell them separately. Some do not. Check before you buy.

The Aftermath

My slow cooker survived. The Tupperware did not. My roommate now knows that “slow cooker” does not mean “reheat anything container.” And I finally made my pot roast—on the stovetop, because frankly, I needed a break.

But next weekend? I’m trying again. This time with the liner. This time with the door closed.

And this time, with a Post-it note on the lid that says:

“NO TUPPERWARE. YES, THAT MEANS YOU.”

I got my first slow cooker last week, and today my roommate thought it was a good idea to heat up—you guess what—in it. This is what happened. Apparently, she didn’t know that you cannot put anything in the slow cooker!