Can You Microwave Rubber?

Q. I got into a fight with my wife recently. She says it is perfectly safe to microwave rubber containers, but I am pretty sure they would just melt! So my question to you is, can you microwave rubber? And if so, does it vary depending upon what kind of rubber it is? I’ve got ten bucks riding on this, so please let me know, can you put rubber in the microwave?

Can you microwave rubber?

A. The quick answer to “can you put rubber in the microwave?” is yes, of course, you can. But you wanted to know something more specific, namely, is it then safe to turn the microwave on? (Ba-dum-tish.)

The answer to that question – can you microwave rubber? – is more complicated. As you surmised, the answer does vary according to which sort of rubber you’re talking about. Modern Rubbermaid containers, for example, are made to withstand the heat of a microwave for the brief amount of time food is generally nuked in: Generally one to two minutes. But when in doubt, always check the bottom of the container; does it say “microwave-safe”? If not, it’s best not to risk it. Just get a plate out of the cupboard.

On a side note, you may have heard that microwaving plastic and rubber containers like these will cause chemicals to leech out of the container and into your food. This is nonsense. If the material is made properly, there will be no leeching of any nebulous “chemicals”. If it’s made improperly, then yes, there will be leeching – of the container itself, as its molecular bonds break down and it melts under the heat of the microwave oven. In that scenario, it will be abundantly clear to you that you should not eat whatever food you just tried to warm up. Either way, you’re not going to be poisoned by it. Same goes for reusing plastic water bottles.

Other kinds of rubber vary in microwave-safeness depending on their durability and what other materials they’re mixed with. Rubber bands, for example, have been known to melt in the microwave. But there are also rubber sheets made specifically to safely absorb and insulate from microwave radiation, which is of course what microwaves use to heat food with. You could microwave those, though I’m not sure why you would want to.

There are actually times when using a microwave to soften up rubber may be in your interest; for example, if you need to use rubber for molding but find that it’s too rigid to work with. In this case, a few seconds should suffice; any longer and you risk outright melting the rubber, rendering it useless and making a huge mess. If you’re unsure about this, though, you may be better off just using a bucket of hot water to better regulate the process.

While we’re on the subject of putting rubber in the microwave, I may as well get these other two definitions out of the way. Pencil erasers are known as “rubbers” in the United Kingdom, but they’re actually made out of a synthetic rubber-like material called styrene-butadiene, with pumice and other materials added in as filler. Microwaving these “rubbers” will melt them, leaving a mess inside your oven. You may want to put them inside a Rubbermaid container if you wish to try this experiment at home.

Condoms (no giggling, please) are also known as rubbers in many parts of the English-speaking world. You also shouldn’t microwave these. Doing this can damage the material, making it more likely to break and just causing all sorts of problems. Please do not microwave condoms.

But when it comes to rubber food containers – a.k.a. the only sort of rubber material that most people would ever consider putting in the microwave – as long as it says “microwave-safe” somewhere on the container or the packaging it came in, you’re good to go. If you’re not sure, then a good rule of thumb to keep in mind is, if it’s dishwasher safe then it’s probably also microwave safe, as similar temperatures are involved in both processes.

Sorry, questioner; you owe your wife a Hamilton.