# Microwaving foam coffee cups? **URL:** \ **Category:** Factual Questions\ **Created:** [August 12, 2012, 12:35am UTC](https://boards.straightdope.com/t/microwaving-foam-coffee-cups/631231 "2012-08-12T00:35:46Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Mdcastle](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mdcastle](https://boards.straightdope.com/u/Mdcastle)\ **Post date:** [August 12, 2012, 12:35am UTC](https://boards.straightdope.com/t/microwaving-foam-coffee-cups/631231/1 "2012-08-12T00:35:46Z")
I tend to keep fast food coffee cups (McDonalds and BK) for a while and use them for their intended purpose, ie drinking coffee, since I dislike ceramic mugs. Is there any reason why I shouldn’t microwave the cups if my coffee gets cold? ---
**Author:** ![ioioio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ioioio/32/316_2.png) [@ioioio](https://boards.straightdope.com/u/ioioio)\ **Post date:** [August 12, 2012, 12:42am UTC](https://boards.straightdope.com/t/microwaving-foam-coffee-cups/631231/2 "2012-08-12T00:42:05Z")
The one time I tried it, the foam cup melted. ---
**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\ **Post date:** [August 12, 2012, 1:00am UTC](https://boards.straightdope.com/t/microwaving-foam-coffee-cups/631231/3 "2012-08-12T01:00:56Z")
> [@laina\_f](#): > > The one time I tried it, the foam cup melted. This, which is pretty much the only risk associated with microwaving food containers, aside from possible [flash boiling](http://www.snopes.com/science/microwave.asp) if you overheat it. For other microwave myths, [here is a nice summary](http://www.cspinet.org/nah/04_05/microwavemyths.pdf) (PDF) of the supposed dangers (some people say that plastic leaches carcinogens but that isn’t true; some plastics do produce dioxins when burned in a fire, but not if simply heated).